KRUEGER AIR DISTRIBUTION BLOG

The Journey Continues

2018-07-05T18:25:00.000-07:00

It has come to my attention that this is my 100th blog entry and that I should think about something special to say. Like all the previous ones weren’t meaningful. HA! Perhaps a bit of reflection now and then isn’t a bad thing.

I attended the Houston Annual ASHRAE meeting a couple of weeks ago. I believe this was my 83rd ASHRAE meeting, but I don’t have data going back that far, as it was before personal computers… A lot has changed since the mid 70‘s when I got involved in the science of air distribution. I had the pleasure and privilege of knowing Dr. Miller and Dr. Nevins of Kansas State who literally wrote the book “Air Distribution”. They, along with industry figures like Harold Straub of Titus and Bill Waeldner of Anemostat, were gracious enough to let me in on the secrets of converting test results into catalogues, both printed, and later, electronic. The Krueger KEC electronic catalogue was released in 1984 for the MS-DOS operating system.

I also got to know Dr. Fanger and Dr. Gagge, who laid the foundations for our understanding of thermal comfort. I worked with those two to get a compromise on a computer algorithm combining the “two-node ET* and the PMV equations. Sadly, the ASHRAE Comfort committee (SSPC 55) is thinking about dropping the “graphical method” of compliance, in favor of computer models which either must be purchased or only run online from a university web site. There is of course, a free graphical model (the only one available) on the Krueger website. (http://bit.ly/2zdLKyr)

I also got to know the outgoing ASHRAE President, Bjarne Olesen, who was a protégé of Dr. Fanger and was who I replaced as chair of Standard 55 when he started his rise to the top at ASHRAE. The current ASHRAE President, Sheila Hayter, is the daughter of Dick Hayter, president of ASHRAE back in the 70’s. He was also at Kansas State back in the day. The involvement of Kansas State in the science of air distribution was a critical one. The ADPI predictions that are used to verify compliance to Standard 55 were developed at KSU in the late 60’s. Recently validated and updated at UT Austin through an ASHRAE research project, the ADPI predictions are valid down to minimum ventilation rates. A heating ADPI prediction is in development from the UTA data.

I went through the development cycle of DDC controls from earlier pneumatic devices in the 80’s. We had to learn that pressure independent airflow control was mandatory if multiple spaces were to be served from a single air source. It would appear that when (not if) ventilation supply is decoupled from comfort control, a pressure independent ventilation control system is also required.

Now, I am involved in the Residential Building Committee at ASHRAE. It seems we are entering the multifamily dwelling industry with about the same level of understanding of the rules for effective ventilation as we did for commercial buildings 40 years ago. I find myself doing the same training on airflow control as I did in the 80’s to a new generation of mechanical engineers who never had any training on this subject. So, job security.

And the wheels keep going round and round…..

Authored by: Dan Int-Hout, Chief Engineer Krueger

Inlet Plenum Claims

2018-06-20T14:54:00.000-07:00

I was asked recently by an engineer whether there is any truth to the claims that a 12” inlet plenum attached to a diffuser would reduce inlet generated sound by ~10NC.

The answer is no, not really. Keep reading to understand why…

There was an ASHRAE research project conducted at UNLV on inlet effects. The short of the story is that diffuser NC values are obtained under ideal test conditions (specified by ASHRAE 70) where there are several diameters of straight duct used. In reality, when you account for the effect of a sharp 90° flex duct bend and realize that rooms don’t really absorb 10dB, the reported value may be underestimated by about 5NC.

At Krueger, we used to sell 90° inlet plenum boxes, but we were shipping mostly air and local contractors could always under bid us. We reported (in 1982) that it would reduce sound by 3 NC.

Where we should be looking is at the ducting…

A straight, hard duct connection to a plenum box will transmit system noise to the diffuser. Even though straight, it may result in being louder than a flex connection, as flex duct has a high “insertion loss” with a low “breakout”, meaning that it makes for an excellent system sound attenuator.

As far as what we've seen in the field, there's often a 90° bend at the connection to the diffuser (outlet). Doing this can seriously affect the discharge pattern. As it turns out, more air will come out of one side, which then results in a longer throw in that direction. In some situations, this may cause occupant discomfort. (PS: This is bad.)

In my experience, air piled to one side by a hard 90° connection will remain piled to one side unless the plenum is HUGE. So to go back to the initial question we were asked, 12” won’t do it, and neither will placing a perforated plate in the path. It will still stay piled to one side. In fact, we found in testing that after 10 feet of 14” spiral duct that follows a 90° connection that the air was still not very uniform at the discharge. So anything that promises to work, just expect that it will add both noise and pressure drop.

In my opinion, I think the approach in unnecessary and likely ineffective. I think it’s better to support the flex duct so it doesn’t lay on the adjacent ceiling tile. Doing this will likely cost a lot less.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Specifying Control Logic

2018-05-03T08:06:00.003-07:00

The controls on VAV boxes have changed quite a bit since their conversion from pneumatic in the early 80’s. Back then, we often referred to overly complex control sequences as ‘Klingon Spaceship controls.’ One would think when DDC controls arrived, that things would be much simpler. Of course, this isn’t what happened.

Instead, we got a proverbial ‘black box’ with “Trust me” written on its side in disappearing ink. Simply broken down, there are two types of controls for VAV boxes, line and block. A line controller is essentially a programmable device with its code written in a ‘line-by-line’ manner. A block controller’s code is written in pre-programmed blocks that work together, hopefully. Technically a ‘line-by-line’ program is broken into functional blocks too. So the question is: What functions are the blocks performing?

It’s difficult to get control suppliers to program controls to do what we expect them to do. We (Krueger) have discussed it a lot with Specifying Engineers and some of our reps. There is a lot of ‘push-back’ from control contractors who want to reuse what they can, and charge the maximum amount for inventing what they feel are new, ‘custom’ sequences. Specifying engineers have told us that they feel the control contractors really don’t understand what the specified products can or should do.

ASHRAE Guideline 36: High Performance Sequences of Operation for HVAC Systems is going to be available this June, and it should provide a basis for writing specifications for VAV systems. I’ll be cutting and pasting from this document to try to put together a guide controls specification for a VAV Series fan box with a sensible cooling coil. Stay tuned for updates!

Authored by: Dan Int-Hout, Chief Engineer Krueger

What A Long Strange Trip It Has Been

2018-04-13T13:52:00.000-07:00

As we train new employees and I look ahead to eventually winding down my career, I tend to look back over my 40+ years in the Air Distribution field. I can say the journey has been, to say the least, interesting.

I started my adventure in HVAC after a tour in the Air Force. I ended up back in the town in Central Ohio, where I went to school (Denison U in Granville, Ohio), with a degree in Biology. I was hired as a “Scientist” in a product testing lab by Owens Corning Fiberglass at their research center there. I got involved in an air distribution problem and joined ASHRAE to learn more about the technology of air distribution. That began my journey in air distribution research, standards and building codes, which continues to this day. I chaired the ASHRAE thermal comfort standard committee (Standard 55), the comfort and air distribution technical committees (one of them twice), as well as several other related technical committees. I even got involved in Acoustics, managing the development of an Acoustical Application committee in AHRI. I was involved in different capacities with the ventilation standard 62.1, and I’m still the air distribution consultant to that committee. I have since become both an ASHRAE Fellow and a Life Member. I even spent three years as a Director at Large of the society, likely the first degreed Biologist to do so.

One of the advantages (some would say disadvantage) of having been around as long as I have is the ability to sometimes see where all this is headed. I was asked by a customer several years ago what I thought would be the “next big thing”. I predicted that someday there would be a requirement to deliver (measured) ventilation air directly into every occupied space. The new Washington State commercial building code requires just that.

Having been involved in the development of VAV from its crude beginnings in the early 70’s, I watched the progression from pressure-dependent to pressure-independent flow control. I also experienced the transition from pneumatic to digital controls. Does anyone still remember how to set pneumatic velocity controllers? What is apparent to me is that we are going through a similar progression with ventilated air. We are still working to get the control sequences we need to be implemented in DDC controllers.

VAV boxes went from system powered and constant volume induction types to parallel fan powered units, then series fan powered units. The ECM motor, introduced 20 years ago (really, 20 years ago?) is now required by code in many jurisdictions, and analog outputs on DDC controls allow fans to vary airflow. This results in variable volume series flow terminal units. We are challenged today with getting controls to properly manage this exciting technology.

Back in 1973, it was difficult to measure low air speeds. The required anemometer was found to have an accuracy of +/- 50 fpm at 50 fpm! I attempted to verify a GSA specification of 20 fpm minimum air speed with this crude device. Working with an anemometer manufacturer, we developed the omni directional anemometer as well as ASHRAE Standard 113, which defined a repeatable method of test for its use. Eventually, we developed methods of predicting air distribution performance using techniques established by a research project conducted by ASHRAE (Then ASHVE) at Kansas State University in the 60’s. The KSU research was validated at today’s lower air flows in a subsequent research project at the University of Texas at Austin in 2013. The premise that “there is no minimum air speed for comfort” (included in the first release of ASHRAE Standard 55 in 1979), was finally validated in a research project that took place in a million square foot building in 2012. Sometimes these things take a while.

While visiting California and Arizona last year, I was promoting the concept of using a variable volume series fan box, (and a sensible cooling coil), to deliver a measured quantity of ventilation air, as well as efficient and flexible operation of economizer (both air side and water side) to commercial spaces. This concept has been in use in Washington DC (starting with the Pentagon) for 16 years. Imagine a concept starting on the east coast and spreading west (instead of the other way around). Operating a series fan box at the lowest possible airflow, while meeting demands, can provide a comfortable environment as well as an energy efficient solution. The energy consumption of ECM boxes has been documented through joint ASHRAE / AHRI research at Texas A&M University. That data is being added to HAP TRACE Energy Plus and other energy use computer programs. Three published ASHRAE journal articles describe the research and its implications.

I am proud to have been involved in all aspects of this technological development. Starting with an impossible specification in a GSA building in 1973, we in the air distribution industry have finally figured out how to effectively and efficiently manage indoor environments in a measurable and controllable fashion. Using ADPI prediction techniques developed in the late 60’s, and validated in the last few years, we can provide design guidance for engineers to lay out air distribution in a way that will ensure occupant comfort at today’s low interior loads, taking advantage of the latest DDC controls and variable fan speed technology. I look forward to assisting the newcomers to this industry as we take the technology into the future.

Authored by: Dan Int-Hout, Chief Engineer Krueger

My Time on the ASHRAE Board

2017-08-01T09:11:00.001-07:00

As many of you know, I served for the last three years on the ASHRAE Board as a Director at Large. It was a three-year term, which ended at the June meeting in Las Vegas. It was certainly an interesting time... I served as ExO (Executive Officer) of two committees: RAC (Research Administration Committee) and the newly formed RBC (Residential Building Committee). As ExO, my function was to ensure that the committees ran well, that membership and leadership functioned properly, and that issues were brought to the Board (through Tech Council, on which I also served).

During this time, ASHRAE established a European Region. This not only helped build alliances with other international organizations, but it gave me an opportunity to spend time with a number of people that I would not have otherwise. And to make it that much more enjoyable, I was also able to continue working alongside others that I've known for years. So, it's no surprise that I was a bit sad to see it come to an end.

Since then, I volunteered for and have been accepted as a voting member on the RBC, where I was previously an ExO. The RBC has been tasked with getting ASHRAE involved in the residential side of our industry, which has received little attention thus far. The overlap between commercial and industrial engineering with residential starts with multi-family dwellings. As such, one of our first orders of business was to develop a multi-family design guide; it should be going to bid soon.

ASHRAE is a rarity in technical societies. It brings together engineers, scholars, and manufacturers for the purpose of researching and developing true consensus standards for the industry. I am proud to have served on the Board and will continue to support ASHRAE in the future.

Authored by: Dan Int-Hout, Chief Engineer Krueger

High Performance Air Systems

2017-05-25T08:40:00.001-07:00

Almost a year ago I wrote a blog about the new code in Washington State. AMCA objected to the wording of the code through several avenues, and was essentially ignored. As I said then, the code mandates “the use of decentralized ventilation systems using dedicated outdoor air systems (DOAS) to deliver 100 percent outside air independent of heating and cooling systems.” This code, in effect, prohibits central station air handlers.

It seems reasonable to assume that the authors of the code were heavily influenced by proponents of “non-ducted” systems, including VRF, WSHP, and Chilled Beams. All these systems require that outside air be carried through ducts to every space, so “non-ducted” is a pretty poor definition.

AMCA had already formed an ad-hoc committee on “High Performance Air Systems”, issuing a white paper this past January. I presented an HPAS webinar on May 4 (2017) to discuss this white paper and an article in HPAC “Specifications for High-Efficiency VAV Systems,” which outlines the requirements and exceptions to the code. The two documents spell out the advantages of “ducted” systems as well as the disadvantages of the other types. Earlier in 2014, I presented a two part HPAS webinar before the Washington code was in place. Both recorded webinars are available on the Krueger website.

I’m a bit surprised that this isn’t front page news. I am more surprised that after visiting engineers in Phoenix, Rochester, Saskatchewan, and Sacramento, there was no awareness of this code change. I have been predicting that one day we would see a code requiring direct measurement and control of ventilation air into all spaces --- and here it is. As it turns out, the “chilled box” I have been touting for the past few years meets most of the requirements of the identified alternates in the Washington State code. As you might guess, I mentioned this in the webinar!

Authored by: Dan Int-Hout, Chief Engineer Krueger

A Look Back

2017-04-05T14:28:00.000-07:00

I’ll be doing another ASHRAE talk, this time in in Sacramento, CA. As I prepared for this trip, I started to think back to when I lived there for a year right out of college, going to the USAF Navigator School at the (now closed) Mather Air Force Base, which is about a mile from where I’ll be giving my talk. What I couldn’t believe is that it has been 50 years!

I served 5 years in the USAF, separating in 1972. A year later, I entered the building construction industry, working for Owens Corning Fiberglass (OCF) in their Product Testing Laboratory, in the same Ohio town where I went to college. Within a year, I reopened their Air Lab to study an issue with a specification on room air motion. It was then that I became involved in ASHRAE and the Air Diffusion Council to better understand air distribution, thermal comfort, and applicable standards.

At OCF, for any claim we published or advertised, we were required to have actual supporting test data (conducted in accordance with established test methods). I have carried that “rule” with me ever since, for 44+ years.

At Krueger, we have a set of folders on the server that hold performance data for every VAV terminal unit and air device for all our printed and electronic catalogs, dating back to 1983, when Excel became available on computers running MS-DOS. We learned in the early 80’s that it was not possible to develop an electronic catalog from printed data. Rather, what we found was that the printed data needed to be produced from the same equations and data used to create an electronic catalog. Krueger’s KEC (Krueger Electronic Catalog) was released in 1984 in MS-DOS. It is still able to run, be it painfully, as it doesn’t use a mouse or function keys (neither of which had been invented yet).

As I train new Krueger employees in the art of data gathering, regression, and catalog preparation (printed and electronic), I hope to instill the spirit of traceable and verifiable performance data that I learned all those many years ago.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Getting Caught Up

2017-03-30T18:26:00.000-07:00

Well, it's March of 2017 and I haven’t posted a blog in 6 months. I guess it’s time.

I last posted a summary of the ASHRAE Journal articles I have had published way back in 2015.

- June 2013 - Slots are Adjustable
- July 2013 - Comfort vs. Energy
- August 2013 - VAV Research Validates Low Airflow Comfort
- September 2013 - Balancing Factors
- October 2013 - You Have to Prove It
- December 2013 - Hospital Operating Room Air Distribution
- January 2014 - Reheat Coil Issues and Answers
- February 2014 - High Bay Air Distribution
- March 2014 - High Performance Air Distribution Systems
- April 2014 - Compliance to Standard 55 (Comfort)
- May 2014 - The Deal about Duct Lining
- August 2014 - The VAV DOAS Fan Powered Terminal
- November 2104 - Proper Selection of Chilled Beams
- January 2015 - Variable Volume Series Fan Box

Since then, I have had three more published, two in the Journal and the final one in the on-line version of the Journal.

- July 2015 - Basics of Air Distribution - This article provided a basic understanding of how well mixed air distribution works in a space.

- October 2015 - History of Fan Powered VAV Terminal Units - Co-authored with another industry colleague, this article traced the history of the fan powered terminal unit in commercial office systems.

- October 2016 - Part of Making Connections - In this, I described how three technical paths, all starting in the 70’s, progressed to finally come together in 2016 to allow new designs to be employed for improvement in acoustics, energy, and comfort.

Planned for this summer are three ASHRAE Journal papers. They will summarize a significant amount of information gained from a study of series and parallel fan powered terminal units performed by ASHRAE and AHRI. These will be co-authored with other industry colleagues.

Authored by: Dan Int-Hout, Chief Engineer Krueger

NW Code Requirements

2016-07-25T06:54:00.001-07:00

The State of Washington has issued a new building code that affects, among other spaces, office buildings. The code is very specific about ventilation and building energy use in that it mandates “the use of decentralized ventilation systems using dedicated outdoor air systems (DOAS) to deliver 100 percent outside air independent of heating and cooling systems”.

What this means is that DOAS systems are mandated and that conventional VAV systems, which mix ventilation and return air at an air handler, are essentially prohibited. While there is an exemption for “High Performance VAV systems”, which I have described in an ASHRAE Journal article and in earlier blogs, it tends to favor those that are disconnected from the ventilation supply, such as VRV and chilled beams.

What is particularly interesting is the requirement that states “ECM motors that vary with load are required for all fan powered VAV terminal units”. This, of course, is what I have been advocating for some time – variable volume series fan box control. When employed with 100% outside air through the VAV inlet (and a sensible cooling coil on the induction port), all the requirements of the new Washington code are met. I’m willing to bet that this will not be the only such code requirement that we’ll see in the future.

Authored by: Dan Int-Hout, Chief Engineer Krueger

ADPI and Standard 55

2016-07-12T11:37:00.005-07:00

I have been campaigning for 40 years to get a correlation between ASHRAE Standard 55 and the concept of ADPI. I chaired Standard 70, (Method of Test, Air Diffusers), Standard 113 (Method of Test, Room Air Distribution, including ADPI) and Standard 55 itself. I also chaired TC 2.1, Thermal Comfort and TC 5.3, Space Air Distribution. I Chaired TC 4.10, Calculation of room air motion (CFD), when it moved from a TG to a TC.

In prior blog posts, I have described the issues with the 40 fpm limit on using the graphical method of Standard 55 to show compliance and wrote an ASHRAE Journal article on how to manage the process. After several false starts, ASHRAE finally approved the creation of a user’s manual for Standard 55. While I was listed as a reviewer during its creation, I was either on the Technical Activities Committee or Standards Activities Committee and felt some conflict of either jurisdiction or time. I have been on ASHRAE’s board for the past two years and have attempted to remain neutral. The process of creating a user’s manual was not without conflicts of opinions.

The document, nonetheless, has been approved for publication. I couldn’t be more pleased with the result. I have attached a tiny piece of the user's manual:

Example 1: Using ADPI for overhead air distribution systems, the diffuser manufacturers often rate their products based on the Air Diffuser Performance Index (ADPI). ADPI is defined by ASHRAE Standard 113 as the percentage of points measured in a room that are within both the ASHRAE temperature and velocity ranges for comfort. ADPI is based on the acceptance and recognition that it is not possible to achieve a comfort level of 100 percent, but 80 percent acceptance is achievable and measurable. Using the example space identified in Figure 3-B, in cooling mode the designer needs to provide 79.6 W/m2 (25.2 Btu/h-sf) of sensible cooling.

As seen in Figure 3-E, the diffuser type is ceiling-mounted with 4-way throw and the return is at the ceiling. Characteristic length of the diffuser is 1.07m (3’-6”) to the wall, 2.23m (7’-4”) to midpoint between diffusers. From Table 4 Chapter 57, ASHRAE Handbook – HVAC Applications, 2011, the closest room load is 63 W/ m2 (20 Btu/h-ft22), with a maximum achievable ADPI of 93, a T50/L of 0.8 for maximum ADPI, and a range of T50/L of 0.7 to 1.3 to achieve an ADPI greater than 90. The designer has selected a diffuser with an isothermal throw of 1.2m (4-ft) to 0.25 m/s (50 fpm). X50/L for this selection is 1.12, which is within the range needed to have ADPI > 80, therefore ADPI requirements are met. Based on ADPI > 80, the designer can conclude that the average airspeed is less than 0.35 m/s (70 fpm) for greater than 80% of the space. The designer can also conclude from the ADPI calculations that the temperature stratification is less than 2.8 °C (5 °F) for locations between ankle and head level (1.8m (6-ft) above floor level) and at least 0.6m (2-ft) away from the exterior wall. In many cases, achieving ADPI of this value will also meet the requirement to not exceed 0.2 m/s (40 fpm) and even 0.15 m/s (30 fpm) if the operative temperature (to) is below 22.5°C (72.5°F). ADPI does not predict air speeds in heating mode, but if the overhead air system is the only potential source of elevated air speed (window drafts have been accounted for with perimeter baseboard heating systems), then it is also likely that the air speed criteria will not be exceeded in heating as the terminal box has been tuned to minimum vent rate in heating mode. See Section 5.5 for more discussion of this point.

The above is what I have been campaigning for as long as I have been in ASHRAE (since 1974). I was asked if referencing the user’s manual was the same as referencing the Standard itself. It would appear that it could. So at last, we have a path to use performance data in our catalog and design documents to be able to claim compliance to major portions of Standard 55.

Authored by: Dan Int-Hout, Chief Engineer Krueger

CO2 is a problem?

2015-11-04T15:07:00.000-08:00

I recently received a link to a new paper on the effect of elevated levels of CO2 on the cognitive ability of building occupants. This explains why student test scores are reported to be higher as ventilation rates increase. While LEED gives a point for increasing ventilation 30% above the 62.1 minimums, the implication here is that the ventilation rate needs to be quite a bit higher than that.

http://thinkprogress.org/climate/2015/10/26/3714853/carbon-dioxide-impair-brain/?utm_source=newsletter&utm_medium=email&utm_campaign=tptop3&utm_term=5&utm_content=5

Currently, outdoor CO2 levels are approaching 400ppm. The report states that while no ‘critical’ level is defined for indoor spaces, the 62.1 DCV (Demand Controlled Ventilation) suggests that it be “700 ppm above outside”, or no more than 1100 ppm total, which is quite a bit higher than what is found to be “safe”. They seem to believe that 600ppm is a good target.

Achieving this will require an efficient means of introducing outside air into a building.

One option is to simply increase the outdoor air setting of the air handler, but most units are designed to handle only about 30% of the unit’s air flow capacity for the climate in which it is installed, so this may not provide enough ventilation. Another option is to increase the percentage of outside air, but that would likely generate limitations with regard to dehumidification capacity and temperature. I believe the most effective method of introducing ventilation is to vary the quantity of ventilation air to the spaces that need it, which would imply the use of a Dedicated Outdoor Air System, or DOAS.

For this concept to work properly, the DOAS unit would likely need to be at a little larger than typical. It would also require an effective delivery system. For it to be energy efficient, it must only deliver as much outside air to each space as is required, which would involve a measured and controlled air flow damper at each zone. The VAV DOAS unit would then supply dry, cool ventilation. Doing this however comes with the risk of sub cooling spaces if the dehumidified ventilation air is not reheated (resulting from minimum ventilation rates that exceed the load).

I’m sure there are other possible means of accomplishing this, but it’s likely that they would not be quite as cost effective as the DOAS solution.

At Krueger, we call our DOAS unit a “Chilled Box”, which is an ECM variable speed, series flow, fan-powered terminal unit with a sensible cooling coil on the induction inlet. I encourage you to read my recent ASHRAE Journal article on this topic, as it not only provides a solution to address this CO2 issue, but it can also satisfy a number of other ventilation challenges you may come across.

Underfloor Products

2015-10-02T14:22:00.004-07:00

With installations taking place in millions of square feet of office space, underfloor air distribution (UFAD) is seemingly gaining in popularity, at least when compared to where it was just a few years ago. In fact, Krueger just recently released their new and improved line of UFAD products that include interior, perimeter, partially stratified, and true displacement ventilation solutions.

As chair of the Technical Committee for the rewriting of ASHRAE’s UFAD design guide, I became much more familiar with the details surrounding underfloor air distribution, both good and bad.

- It provides a truly flexible solution and is great for high-churn applications.

- It allows users to be in more control of their comfort by way of controlling the flow of air in their immediate space.

- It requires careful coordination with all the construction trades to avoid the loss of conditioned air into unwanted spaces (leakage).

- Designs must take into account the perimeter to properly handle solar loads. (This can be said for any form of air distribution!)

- There must be controls in place to maintain humidity control. Should moisture issues arise, they may not be apparent until it has caused a more severe problem.

Luckily though, with proper planning and when you can find the right partners and product mix, all these details can be addressed to ensure a successful UFAD system. (Of course, with the products come the expertise and guidance from the supplier - like Krueger, who has installed many successful UFAD projects.) So, if you haven’t already, take another look at UFAD, it’s a proven technology that can offer many benefits to building owners and occupants.

Learn about Krueger’s new line of underfloor products.
https://www.krueger-hvac.com/Catalog%20Home/Underfloor

Top Ten HVAC Predictions Scores for 2014

2015-02-06T13:10:00.003-08:00

Now that a certain event has past (weekend before last) I can finally score myself on my predictions for last year.

1. LEED V4, released last fall, includes a reference to either AHRI 885 or the ASHRAE Handbooks to prove compliance to acoustical requirements. The handbooks are missing a critical path table for the sound transmitted from a plenum noise source into a space. The incoming chair of TC 2.1 has indicated he will get the missing ceiling table included in the Handbooks. I predict he will fail in this effort for at least three years and that the 885 handbooks will be the only easy path to compliance. (One can hire an acoustician, of course, and TC 2.6 is populated with them). Yup. Nothing happening - 10 points.

2. Installed linear diffusers will still fail to have pattern controllers set prior to balancing. If adjusted after balancing, rebalancing is required. It is the design engineer’s responsibility to provide the adjustment information. The installing contractor should be designated as the one responsible for setting the pattern deflectors. I saw close to 1000 Engineers last year. Only a couple admitted it was their responsibility to specify who was to adjust them and to provide instructions. The NEBB says in their basic instructions it is their responsibility. No balancer I spoke to knew this or did it - 10 points .

3. ASHRAE Thermal Comfort Standard (55-2013) has been modified to include Normative (mandatory) and Informative sections so that it can be referenced directly in codes. ADPI will be included by reference to the ASHRAE Handbooks, which will be updated to show the relationship between air distribution and thermal comfort. Well, this didn’t happen. The ball got dropped somewhere. My bad - 0 points.

4. There will still be no new published, peer reviewed, energy savings data for any of the “energy saving” systems (VRF, displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems, to get LEED or Energy Star ratings. Yup. No data - 10 points.

5. The AHRI / ASHRAE study on whole system energy use of fan powered boxes will begin to be integrated into the Energy Plus and possibly Trane Trace and Carrier HAP energy models under an AHRI research program. Underway. An excellent paper will be presented in June - 10 points.

6. The number 1 reason for not renewing the lease in high rise buildings will continue to be “occupant dissatisfaction with the building environment” (ie: comfort). It has been so for the past 20 years and is frankly a ‘gimmee’. One can hope that I miss this one. The BOMA public relations person now refuses to answer this question. I guess they are a bit embarrassed by the data. I’ll give myself 5 points.

7. The market for HVAC components will again be up about 5% with pent-up demand slowly coming back. Slowly but surely it is - 10 points.

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load. ASHRAE RP 1515 will open a lot of eyes. The report from the ASHRAE MTG on Advanced Air Distribution will be circulated showing paths to optimize system design. The MTG says it has completed its work and has been dissolved. About 20% of the engineers I spoke to have lowered their interior design from 1.0 to 0.65cfm/sf. - 8 points

9. While many VAV box schedules will continue to show design discharge temperatures in excess of 90°F, a number of Engineers will finally get it. (ps: Hot air rises!) I still get push back on this issue, but some are getting it. It’s getting better, but we’re still not there yet - 8 points.

10. Sadly, I predict that the Cowboys will continue to wallow in the mud of disappointment. Ok. I blew this one. Of course, the Cowboys blew the last one! But, I’m still giving myself 0 points.

So I get 71 out 100. That’s just a barely passing grade… but seems familiar some how. I’ll try to do better this year.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Top Ten HVAC Predictions for 2015

2015-01-28T07:15:00.002-08:00

It’s time for my long awaited top 10 predictions for 2015. I am becoming a bit pessimistic in my predictions. If I get a high score next January, it will mean the industry has failed its customers - building occupants.

1. LEED V4 will get less and less buy-in. Since there is no enforcement or post construction check, the LEED rating has no teeth --- but it gets “feel good” points from the “greens”. None from me though.

2. Installed linear diffusers will still fail to have pattern controllers set prior to balancing. Sadly, this is likely a gimmee. When asked, neither balancers, contractors, or design engineers take any responsibility for assuring this gets done. Building occupants will suffer, but everyone else gets paid.

3. The Variable Volume Series Fan Powered Box will be recognized as a really effective way to design an energy efficient HVAC system.

4. There will still be no new published, peer reviewed, energy savings data for any of the “energy saving” systems (VRF, displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems to get LEED or Energy Star ratings. This is likely another gimmee, but I can hope.

5. The AHRI / ASHRAE study on whole system energy use of fan powered boxes will start to be integrated into the Energy Plus and possibly Trane Trace and Carrier HAP energy models under an AHRI research program. This is one I hope I win.

6. The number 1 complaint I hear is that offices get cold in the afternoon. No kidding. Design loads are overestimated by likely a factor of five. I predict this will not change in 2015… Another one I wish to lose.

7. The market for HVAC components will again be up about 5% with pent-up demand slowly coming back.

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load.

9. While many VAV box schedules will continue to show design discharge temperatures in excess of 90°F, a number of engineers will finally get it.

10. The Cowboys will prove to be unpredictable. After last season, one has hope, but I wouldn’t bet any money. I predict a 9-7 season.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Engineers Push Back

2014-09-03T06:42:00.000-07:00

I recently received a nice letter from an engineer in California who said she had heard me speak a few years ago about overhead heating and had been following my advice (and that in 62.1 and the Handbook) about limiting discharge delta-t to 15oF. She then went on to say how surprised she has been at the push back from engineers on this recommendation. Sadly, I had to tell her that my experience has been similar.

In my role as an ASHRAE Distinguished Lecturer and in making engineering sales calls with Krueger Reps, I see an average of 1000 engineers a year. I almost always manage to bring this topic up in conversations or lectures and nearly every time, there’s an engineer that tells me, “I’ve been doing this for XX years and no one has complained”.

Apparently, the concept of hot air rising (and cold air falling) isn’t a universally accepted paradigm when it comes to air distribution. This person (California engineer) mentioned that there is disbelief in my stated rule on heating a room, where “the hotter the air delivered at the ceiling, the longer it takes to heat a room.” Sorry folks, but it’s true - overly hot air dispensed at the ceiling will most certainly want to stick to it. The hotter it is, the longer it will stay stratified, which means the longer it will take to cool enough to blend with the air below in the occupant space.

Every forced air project with a heating coil likely has an equipment schedule. Somewhere on that schedule is a column headed ‘Leaving Air Temperature’. If any values in that column are 15°F greater than the designed zone temperature (usually between 73°F and 75°F), the code official has the right to ask how the engineer intends to comply with the Standard 62.1 requirement for increased ventilation air and if that requirement was included in the building load calculations. If you recall, ASHRAE Standard 62.1 requires an additional 20% outside air if heating from the ceiling with a ceiling return, as is the case in most commercial buildings. The 62.1 Ventilation Rate Procedure has been adopted by many, if not most building codes.

It’s also worth noting that any space with a discharge to room differential exceeding 15°F will not comply with the vertical stratification limitation of ASHRAE Standard 55, which is often included in many codes, if not a minimum in building design assumptions. Still, engineers are pushing back. It’s no wonder the level of discomfort in commercial spaces is as high as it is. But as they say, “who’s checking?”

Do you work in a stuffy building? Are you using a space heater year round? Tweet us @KruegerHVAC and share your comments with the HVAC engineering community. Let them know that regardless of #whoschecking, proper air distribution matters.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Air Leakage

2014-07-22T07:33:00.002-07:00

Not too long ago, I attended my first ASHRAE meeting as a member of the Board of Directors. My time at the meetings has, for the most part, been focused around participating in the Tech Council and being a board representative on RAC (at least for one year). It’s a busy job, but someone has to do it!

As for recent happenings, I have received quite a few questions about air leakage. Ironically, there has also been a push from the 90.1 committee for VAV box manufacturers to “come clean” about air leakage rates. Just to give some history, a couple years ago the AHRI section that covers VAV terminals was asked to come up with leakage numbers. Several manufacturers put numbers on the table for single duct and dual duct boxes, as a function of size and type of heat. This data was presented to those requesting it. They then asked, “So when will you start certifying the data?” The answer is never. Not only is the required test setup expensive to run, but there are a number of uncertainties involved. With regard to cost, if for some reason a test failed to be certified, the penalties are so expensive that it would most certainly warrant an increase in cost, which we know would not be received well by customers. (Then, to make matters worse, there is little payback for the slight reduction in leakage that would result for single or double duct units.) So, when we informed the interested parties that there would not be a certification program, their response – to our surprise – was “then, never mind”. However, there have been rumors that the DOE is pushing the 90.1 committee to bring it up again.

Fan boxes, on the other hand, are a different matter. For starters, a both series and parallel fan boxes, for the most part, are under negative pressure, so leaks would be in the unit, not out. This is definitely the case for series boxes. For parallel boxes, half the unit is at a slight positive pressure, but it is probably no more than 0.5”, which is just enough to feed the downstream diffusers and ductwork, and possibly a water coil. The backdraft damper on parallel boxes, however, is seldom robust enough to effectively provide a tight seal. The ASHRAE/AHRI project evaluating series and parallel boxes at Texas A&M University found that a typical parallel box will leak between 10% and 15% at typical pressures. Of course, this could be significantly reduced, but as mentioned earlier it would add significantly to the cost of the unit and require an actuator and actuated damper. We have not (yet) seen any specifications calling for this degree of air tightness. The A&M report also stated that a parallel box would have to leak less than 7% to be more cost effective than a series box, from a total system standpoint.

So that’s where the industry is at this point with regard to air leakage. I expect that we will hear from the DOE in the future and that certain the rules will be tightened up, but sadly, the efforts are likely to generate little actual energy savings.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Is it May already??

2014-05-07T14:19:00.003-07:00

Sadly, ASHRAE still hasn’t published the letter to the Editor from our Engineering Manager on the Hospital OR article that made the cover of the Journal in February. (The one I wrote last year has received no comments.) The other articles I wrote have all been posted on our website under Learn > White Papers.

The big news is, of course, the purchase of Air Distribution Technologies (our parent company) by JCI (Johnson Controls). We have been assured that business will continue as always. The best part is that we are no longer being owned by a “holding company,” where our future was rather uncertain. We hope, of course, that the purchasing power and vast industry knowledge of our new owners will provide us with an array of new opportunities that will allow us to serve our customers better.

All that being said, I will continue towards my role as a member of ASHRAE’s board, effective after the summer meeting. I have been appointed to the Tech Council, where I will be able to see the ins and outs of technical activities. I was asked to prepare a short statement in response to the question “As ASHRAE moves ahead in developing a new strategic plan, what are the strengths of ASHRAE that we must not lose sight of?” I responded with the following, as printed in the April ASHRAE Insights.

“ASHRAE has a unique membership composed of manufacturers, academics, and design engineers. We need to make sure we take full advantage of the research capabilities and manufacturing expertise to provide the design community with the truly innovative, thoroughly tested, and affordable products and systems that meet our core goal: that of providing acceptable environments for the occupants of buildings that we heat, cool, and ventilate. In this way, we can ensure that healthy and comfortable folks continue to provide a record level of productivity in the workplace and at home. It would be an added bonus if we could, at the same time, minimize our impact on the environment by reducing energy use and minimizing unsustainable activities."

Authored by: Dan Int-Hout, Chief Engineer Krueger

Krueger-HVAC Response to ASHRAE Journal Article on "Hospital OR Air Distribution"

2014-03-27T14:12:00.000-07:00

In February, there was an ASHRAE Journal article on Hospital OR Air Distribution. After thoroughly reviewing it, we identified several technical flaws. It’s worth noting that the article I authored on the same subject was published in December 2013 (with quite different conclusions, I might add). Now with 11 articles having been accepted by the Journal as of recent, only a few are posted on our website, unfortunately. We will make them available as soon as we get approved copies from ASHRAE.

In response to the article, a letter to the editor was prepared by our Engineering Manager and will hopefully be published soon. Below is a quick summary of what was sent:

Summary of letter to the editor on “Improving Operating Room Contamination Control”

The authors incorrectly state the four different ceiling air delivery scenarios meet ASHRAE Standard 170 guidelines for diffuser coverage over the patient table.
The AC system doesn’t comply with the Space Ventilation requirements stated in section 7.1.a of ASHRAE Standard 170-2013.
Based on the sizing of the AC system, one could also question the results for the MDA system.
Splitting the MDA array completely across the table is one of the worst possible configurations for this type of system, especially since it happens right in the middle of the surgical table where it can induce contaminants rising from the patient.
The author gives the room dimensions as 20 ft 5 in. W x 20 ft 7 in. L x 10 ft H for a room volume of 4,202 ft3 but uses a room volume of 4,800 ft3 to 4,822 ft3 for their ACH calculations.
The author makes the statement – “The data also indicates that at equal size and airflow, a one or two ISO Class improvement was achieved between the MDA and SLD1 scenarios without additional energy consumption.” The data shows only a single ISO Class Improvement from ISO Class 8 for the MDA-30 to an ISO Class 7 for the SLD1-30 for systems complying with ASHRAE Standard 170-2013.

While this article is a good starting point for generating dialog on hospital OR environments, the study itself is flawed and looks to be more of a marketing/promotional piece for manufacturers of SLD systems.

The results are at odds with both the testing conducted by Krueger in the 1980’s with actual patients and with the Egyptian study I referenced in the ASHRAE Journal article (“Air Distribution in the OR”, December, 2013). This is to say, we are convinced that a properly designed air curtain system will provide the safest form of air distribution in a hospital setting.

BTW - Stay tuned to the Krueger website for exciting clean room developments soon to be released!
www.krueger-hvac.com

ASHRAE Articles Authored by Dan Int-Hout (Update)

2014-02-20T10:47:00.001-08:00

Now that we are settled after the January ASHRAE meeting, I have some interesting news to report. I have been named a Director At Large (DAL) for ASHRAE. I’ll be traveling to Atlanta at the end of January for training and then I’ll be able to report on what my duties will be. I will of course be attending all meetings of the Board of Directors, either in Atlanta at annual meetings or on-line. I am very excited about being able to use my experience as an ASHRAE member for 40 years to help the Society move forward. My tenure will be for three years, starting officially in June.

I now have 10 articles submitted or published in the ASHRAE Journal. I reported earlier on the first set, here are the summaries:

June 2013 - Slots are Adjustable
July 2013 - Comfort vs. Energy
August 2013 - VAV Research Validates Low Airflow Comfort
September 2013 - Balancing Factors

I reported on some of the details of these in a blog in September last year.

New are:

October 2013 - You Have to Prove It
Validation of computer models is necessary to prove that the input assumptions, and the math used is valid. All too often we are seeing estimates that just don’t pan out in practice.

December 2013 - Hospital Operating Room Air Distribution
I reported on the understandings of how air curtain systems in Hospital OR’s have been proven to be an effective way of reducing infection rates, the current article in the February issue notwithstanding.

January 2014 - Reheat Coil Issues and Answers
Hot water coils are being designed with cooler entering water than in the past and it is causing some selection issues. I discuss minimum flows, and issues with electric heaters as well.

February 2014 - High Bay Air Distribution
Providing temperature control and comfort in locations with high ceilings is always a challenge. I have provided some easy ways to estimate the effect of buoyancy on delivered air flows.

March 2014 - High Performance Air Distribution Systems
An ASHRAE multiple discipline task group (MTG) is looking at how to design air distribution systems for maximum efficiency and sustainability. I have offered the spin on the terminal end of things.

April 2014 (Just submitted) – Compliance to Standard 55 (Comfort)
Compliance with Standard 55 (Comfort) can appear to be complicated. I have offered a bit of history on the calculation methods and have shown an easy path to compliance.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Cold Calls – “Our Electric Coils Aren’t Working”

2014-01-15T08:00:00.000-08:00

With the record cold that has gripped the country, the last thing one wants to hear is that the heat isn't coming on! So, we looked into the issue and have found that in most cases, this complaint stems from the design engineer not understanding some basic facts regarding the proper use of a VAV reheat air terminal device.

The typical complaint we get on electric heat is that it doesn't come on because the airflow safety switch isn't “making”. There are several issues that need to be understood:

1. Energizing: With today’s DDC systems, there is always low voltage available and electric heat is energized through electronic relays. In the past, these were typically wire wound electromagnetic coil relay devices, triggered and powered by low voltage current. As of recent, we are employing solid state relays, which although more expensive, are silent. With older pneumatic systems, the circuitry was all high voltage, which sometimes caused issue with arcing across the contacts in the safety “sail switches”.

2. Safety: UL specifications (and logic) require that the electric heat not operate unless there is sufficient air flow across the coils. After the main relay that energizes the electric coils, there is an airflow proving device and an overheat “high limit” device and on Single Duct units, there is a manually re-settable high temperature thermal cutout.

3. Airflow Proving: The air proving device used in all Krueger boxes is a “sail switch”, which is actually a combination of a membrane and micro-switch. This is used as a differential pressure assembly with only the high side connected to a pickup in the air stream. The low side is typically open to the control enclosure. On some airflow switches, there is no connection tap on the low side. If the switch is installed in a relatively air tight enclosure, this can be a problem, so Krueger has elected to only use higher cost switches with a low side tap so we can reference the differential pressure outside the cabinet if desired.

4. Air Flow Pickup: The single point pickup probe is located at the point of highest airflow in the heater assembly. The single tube pickup is actually a “total pressure”, rather than a velocity pressure device, which would require two tubes.

5. The mechanics of this type of sail switch precludes a tight operating range specification, with the one Krueger uses having an 0.05” stated response, but with an accuracy of +/- 0.02”. We find that most operate (make) at about 0.03”. The published minimum airflows in the Krueger catalog develop less than 0.01” velocity pressure at the probe location, so Krueger requires that there be at least 0.03” downstream pressure in the airflow path to the room to get the necessary total pressure to engage the airflow switch.

So, knowing the “rules”, we can now look at the issues they raise. If a single duct VAV box is set to have heat come on at minimum VAV box airflow settings, it is very unlikely that downstream pressure will be as high as 0.03. If it were, and if the box is set at the typical 25% of cooling maximum air flow, the downstream pressure would 16 times higher at maximum flow! For a typical single duct VAV box electric heater, this is about 0.4”. Few systems are set to operate with downstream pressures this high.

This is compounded by the damper position in the VAV box. Even though we require a longer box when using electric heat, we still see a higher velocity pressure at the pickup location at partially closed damper positions than when the damper is fully open. With dynamic air handler system pressures being set so that at least one box has a fully open damper (as required in some codes), it is possible that a perimeter heating VAV box may have a fully open damper, but then it may not “make” even at the Krueger stated minimums. A balancing damper set to provide some back pressure may be required in some extreme cases.

In most cases, it shouldn't be a problem, that is, if the engineer is following good practice (and most codes) and limiting discharge temperatures to 90°F. This will usually require heating airflows to be higher than 25% of cooling maximums to meet the heating load requirements. DDC controllers make having a “dual minimum” as simple as just setting it up. (Older pneumatic systems require complex plumbing to achieve dual minimum control). The ASHRAE 90.1 energy standard, typically referenced in codes, now allows for reheat up to 50% of design cooling air flows if one starts at 20% and limits discharge temperatures and uses VAV heating. Of course, Krueger’s LineaHeat electric heat was designed with this as a standard feature should one add a temperature probe located downstream of the heater.

So in summary, a VAV box with electric heat will operate properly when the heating airflows are high enough to provide sufficient total pressure at the heater. This can usually be accomplished with sufficient airflow to meet the 90°F discharge limitation. If lower airflows are required, providing some static pressure resistance downstream may be needed.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Top Ten HVAC Predictions for 2014

2014-01-08T06:15:00.000-08:00

1. LEED V4, released last fall, includes a reference to either AHRI 885 or the ASHRAE Handbooks to prove compliance to acoustical requirements. The handbooks are missing a critical path table for the sound transmitted from a plenum noise source into a space. The incoming chair of TC 2.1 has indicated he will get the missing ceiling table included in the Handbooks. I predict he will fail in this effort for at least three years and that the 885 handbooks will be the only easy path to compliance. (One can hire an acoustician, of course, and TC 2.6 is populated with them).

2. Installed linear diffusers will still fail to have pattern controllers set prior to balancing. If adjusted after balancing, rebalancing is required. It is the design engineer’s responsibility to provide the adjustment information. The installing contractor should be designated as the one responsible for setting the pattern deflectors.

3. ASHRAE Thermal Comfort Standard (55-2013) has been modified to include Normative (mandatory) and Informative sections so that it can be referenced directly in codes. ADPI will be included by reference to the ASHRAE Handbooks, which will be updated to show the relationship between air distribution and thermal comfort.

4. There will still be no new published, peer reviewed, energy savings data for any of the “energy saving” systems (VRF, displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems, to get LEED or Energy Star ratings.

5. The AHRI / ASHRAE study on whole system energy use of fan powered boxes will start to be integrated into the Energy Plus and possibly Trane Trace and Carrier HAP energy models under an AHRI research program.

6. The number 1 reason for not renewing the lease in high rise buildings will continue to be “occupant dissatisfaction with the building environment” (ie: comfort). It has been so for the past 20 years, so this is likely a ‘gimmee’. One can hope I miss this one.

7. The market for HVAC components will again be up about 5% with pent-up demand slowly coming back.

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load. ASHRAE RP 1515 will open a lot of eyes. The report from the ASHRAE MTG on Advanced Air Distribution will be circulated showing paths to optimize system design.

9. While many VAV box schedules will continue to show design discharge temperatures in excess of 90°F, a number of Engineers will finally get it. (ps: Hot air rises!)

10. Sadly, I predict that the Cowboys will continue to wallow in the mud of disappointment.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Scoring on My Top Ten HVAC Predictions for 2013

2014-01-02T09:01:00.001-08:00

1. LEED 2013 will be released in the fall, and it will include a reference to AHRI 885 to prove compliance to acoustical requirements. Done - 10 points

2. Balancers will continue to ignore the need to adjust linear diffusers before balancing. If adjusted after balancing, rebalancing is required. This is the design engineer’s responsibility, of course, so they need to require adjustment is they specify adjustable slots. I predict this will be ignored. (It’ll be an easy 10 points). Yup - 10 points

3. ASHRAE Thermal Comfort Standard (55-2010) will be modified to include Normative (mandatory) and Informative sections so that it can be referenced directly in codes. This is already partly accomplished. ADPI will be included in ASHRAE standard 55 as a means of predicting compliance. In progress - 7 points

4. The updated ASHRAE UFAD Design Guide will be published in 2013. Done - 10 points

5. We will see no published, peer reviewed, energy savings data for any of the “new” systems (displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems, to get LEED or Energy Star ratings. Sadly, still no published validation - 10 points

6. BOMA will continue to state that the #1 reason for not renewing the lease in high rise buildings is “occupant dissatisfaction with the building environment” (ie: comfort). (It has been for the past 20 years, this is likely a ‘gimmee’.) Still the top reason - 10 points

7. The market for HVAC components will again be relatively flat with local ups and downs. Still flat - 10 points

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load. ASHRAE RP 1515 will open a lot of eyes. Yup - 10 points.

9. The majority of VAV box schedules will continue to show design discharge temperatures in excess of 90F, in spite of the ASHRAE handbook stating this will guarantee non-compliance to Standard 55’s vertical temperature stratification limitation, and without compensating increases in ventilation, as required by Standard 62.1 (and code in most states). Again, this is sadly true - 10 points

10. Sadly, the Cowboys will continue to disappoint their fans. (Again) I’m tempted to give this bonus points, but I’m in a giving mood – 10 points.

97 Points total. Nostradamus has nothing!

(It’s easy to score high if you grade your own predictions….)

Authored by: Dan Int-Hout, Chief Engineer Krueger

Vertical Stratification Limits

2013-11-11T11:12:00.000-08:00

In their infinite wisdom (just ask them), the academics on the ASHRAE Standard 55, Thermal Comfort, are proposing that the 5°F vertical stratification limit be only for seated persons, and that standing persons should be allowed 7°F or more. I posted the following to members of the committee.

While it is a wonderful thing that we are looking to research and make our standard as accurate as possible, we are missing the forest for the trees. An academic approach is certainly defensible, but sadly, it is of little use to the design engineer. The number one reason for occupants not renewing the lease in commercial spaces continues to be, as it has for the last 25 years, occupant dissatisfaction with the thermal environment.

The majority of commercial spaces in North America are supplied with overhead, well mixed air distribution systems, and a huge percentage of these are VAV. If air outlets are not designed to work at low flows, the space becomes stratified. Since hot air rises (I know this is obvious to all the academics on this committee, just not to many practicing mechanical engineers), it becomes cold at the floor. The only tool available to convince engineers this is an issue is Standard 55 – and you are all conspiring to take that single tool and throw it out the window.

I was asked to chair TC 2.1 back in ’78 because I was the only non-academic on the committee who was willing to express an opinion at that time. I was also involved in Standard 55 at the same time, again as a non-academic, trying to force some real world logic into the standard. As an ASHRAE DL (Possibly the only one on this committee?), I see over a thousand mechanical engineers, contractors and sales reps a year, and have done so for 20 years. The practicing engineer is woefully ignorant of the nuances of Standard 55 and has a lot of other things to worry about. But, they are most often hired by the architect, and often seeking LEED accreditation. Compliance to Standard 55 is only one point out of 100 (that’s 1% for any non-academics who might read this). Requiring analysis of a project at the design stage leaves few tools for the ME. ADPI is one that can at least be performed using software, which is available from a number of manufacturers. We on the manufacturing side have shown for many years that an ADPI of 80% of greater ensures a vertical stratification that meets the 5.4°F limitation in the present standard. The GBCI reviewers have accepted this in a number of cases, as reported to this committee in the past.

More importantly, using ADPI analysis, one can easily show that several types of air outlets do not perform well at turn down, particularly the face mounted deflector perforated outlet. This was at one time the highest selling type of air outlet in North America, due in part because it was the cheapest. Thanks in large part to Standard 55, it has, thankfully, fallen from favor, despite architects’ wishes. Standard 55 and LEED have been tools in this conversion, forcing architects to use a better performing device. The “swirl” diffuser, so highly promoted (touted?) by our European friends, also performs poorly at low airflows (VAV is seldom used in Europe).

Opening the vertical stratification limit to greater than 3°C eliminates ADPI as a limiting design factor. While Gwellen is correct in stating that an ADPI of 80% is assurance of meeting Standard 55 (and that it is not necessarily so in reverse), it is the only tool available to the design engineer. (CFD has not, to date, been shown to be a validated method of predicting air distribution performance, at least not in any peer reviewed papers readily available – I’m sure Peter has several that he can let us peek at, but cannot be circulated).

Overhead air distribution assumes a well mixed space. 3°C in a 6’ high comfort zone is a pretty well mixed space. 4 or 5°C is not. Well mixed spaces are necessary for thermostats to function properly. When air outlets “dump” at low flows (ok, exhibit “excessive drop” for you academics), not only is it cold at the floor where those not wearing socks will be uncomfortable (which applies to most women working in offices, and likely some males, especially in Berkeley), but thermostat response is significantly longer. I know of one courtroom where the thermostat response went from 55 minutes to 5 minutes by fixing the ceiling air distribution to stop it from ‘dumping’. I have repeated this many times in a number of places by simply adjusting the diverters in slot diffusers to produce a horizontal air pattern. Allowing non-well-mixed air distribution, which opening up the vertical stratification limit will permit, will have the effect of allowing the architects to again select air outlets that perform poorly at low flows, which will result in greater occupant dissatisfaction and poor thermostat response. It will also allow installing contractors to ignore the requirement (sadly seldom enforced) that adjustable slot diffusers actually be adjusted. With an allowed 6 or 7°F vertical stratification, we are in effect saying “what does it matter?”

It does matter, though. We are doing a horrible job of designing comfortable spaces. If you would actually get out there and ask folks how they feel, you might get some idea of the extent of the poor comfort conditions we have created. Almost all the complaints are “it’s too cold at the floor”, followed by “it’s too cold”, period. Resetting VAV minimums lower, eliminating code required dead bands (which force the system to control to 68°F once they go into reheat as a result of sub cooling), and using air outlets that perform well at low air flows are all strategies that need to be implemented. Opening up stratification limits, which may be technically accurate, is only going to allow us to continue our apparent practice of creating uncomfortable spaces, which will now comply with the Standard!

The law of Unintended Consequences is about to rear it’s ugly head. Sadly, I fear I will once again be able to say “I told you so”.

My ASHRAE Journal Articles

2013-10-09T12:36:00.001-07:00

I now have 5 of the 6 promised articles published in ASHRAE Journal. The first 4 are posted in the newly redesigned Krueger website under the menu “Learn” > "White Papers" (http://www.krueger-hvac.com/public/learn/white%20papers).

#1 - The first article was about adjusting adjustable diffusers, primarily linear slots (which are seldom adjusted, it seems). In discussions since the publication of this article, I have learned that this is likely a major cause of occupant discomfort in office spaces, as it seems no one ever adjusts them. When slots blow down, they create significant stratification in the space; cold air settles to the floor without very much mixing; hot air rises and the thermostat thinks the room is satisfied, which is true only in a thin layer the same distance above the floor as the sensor. The resultant cold layer causes great discomfort for those occupants not wearing socks; leading to the ubiquitous 1500 watt heater. Perhaps, more importantly, the thermostat response is greatly slowed in this scenario, often 10 times slower than when properly mixed at the ceiling. Adjusting the diffuser then requires that it be rebalanced, which is best done at installation. A combination of instructions from the specifying engineer to the installing contractor is likely the best path to getting this done.

#2 - The second article was on the tradeoff between energy and comfort. As I reported in my last blog, this one drew comments from a couple energy zealots who, apparently, are still not convinced that making people uncomfortable in order to save energy is counterproductive in terms of both energy and cost. I suspect that anyone who makes a living as an “energy consultant” has misplaced priorities. Worse, there doesn’t seem to be a market for “comfort consultants” to counter them – and there should be, as salaries are on the order of 100x energy costs in most buildings. If we are not careful, we will have buildings that qualify as “Net Zero Satisfaction Buildings (another article I wrote for ASHRAE last year (http://www.krueger-hvac.com/files/white%20papers/article_net_zero_acceptability.pdf).

#3 - The third article was on the validation of high turndown VAV systems, based on recent ASHRAE research conducted on several California buildings. Two significant results (in addition to others) were that loads are so low in a modern office interior zone that spaces are often sub cooled, and that operation at very low air flow rates, with good diffusers (plaque-type, in this case) provide excellent occupant responses. This opens the door for a number of energy saving strategies, including variable volume series fan powered terminal units and fan coils using ECM motors. In both cases, however, maintaining proper code required ventilation rates requires measured and controlled ventilation dampers. There will be an article on this subject in the ASHRAE Journal in the near future from another contributor (who beat me to the punch!).

#4 - The fourth article was on the issue of area factors for balancing diffusers and discussing why we really can’t publish them anymore, as the choice of the instrument used to measure discharge velocity from a diffuser has become a significant variable in the calculation of the constant to convert velocity to air flow rate. The old stand-by, Alnor Velometer, is seldom used anymore, as the new digital anemometers can store and average data. Sadly, they all respond quite differently to the thin high velocity air jet that is created by today’s air outlets, so there is no single Ak for any device, rather, each device has a different factor. Our advice is to carefully measure the airflow rate for one diffuser/zone on a project and then determine the Ak for that diffuser and velometer.

#5 - The fifth article, which we haven’t yet posted because we haven’t yet received a web-friendly copy back from ASHRAE, is about the lack of validation data on calculations/predictions of a number of building variables, including air motion, energy, and acoustics. The result is that energy predictions often fall far from the mark; spaces are noisy and occupants feel drafts. None of the available building energy programs properly account for the energy consumption of either series or parallel fan powered terminal units, which typically overstates (grossly) the energy use of those with ECM motors. While the savings from variable flow ECM series fan boxes is obvious, one has to “make up” the calculations. Similar issues are found for displacement, underfloor, and chilled beam systems. A literature search will turn up almost no actual energy use data for any of these “energy savings” strategies. Calculation of acoustics for ducted devices is in much better shape, as AHRI 885 has been in place, with a spreadsheet, for a number of years. All that is required is octave band sound power for the devices in question, which has been certified for VAV boxes for many years via the AHRI 880 program. Other ducted devices can be tested to AHRI 260. LEED V4, out this month, will recommend AHRI 885 for proof of compliance with the 40dBA HVAC sound levels prerequisite in classrooms.

I’ll be working on the 6th article, scheduled for December ASHRAE Journal over the next week. It will either be on water coil calculations for VAV boxes, or on the many “magnification factors” being used to define the performance of inlet probes on VAVC terminals. Stay tuned….

Authored by: Dan Int-Hout, Chief Engineer Krueger

ASHRAE Journal Articles

2013-08-29T12:43:00.000-07:00

I have had 4 of the 6 promised “Engineer’s Notebook” articles published in the ASHRAE Journal. I received permission to post these on the Krueger website, which I will do as soon as they send me back the “approved” versions. We’ll update this blog entry with links as soon as they become available.

I have had a lot of very positive feedback from these articles, but today I got my first negative critique. The responder, a consultant (I assume an energy consultant) from Seattle, complained that “this kind of thinking will prevent ASHRAE from progressing the art of design”. I responded with this:

While I fully agree that oversized equipment may lead to occupant dissatisfaction, as the system attempts to operate efficiently at part load (see my most recent article in the Journal ), there are a large number of "energy efficient" buildings where occupant comfort has taken a back seat to energy savings. Following the publication of the article in question, I received a comment regarding a government building in your city, which is going for an energy award with both Underfloor Air Distribution (UFAD) and Chilled Beams. An occupant posted a picture on the internet of a temperature sensor on his desk indicating it was 90°F there. I'm sure they will have low energy use, but at what cost? Supposedly, there are umbrellas duct taped to office dividers to keep the sun off the occupants.

I fully agree that "Energy efficiency does not make buildings uncomfortable; but the lack of good mechanical engineering design does." Sadly, so does poor understanding of how a building is supposed to operate. Innovative systems need much more building operations training than more traditional ones. Construction of innovative designs is also often compromised by poor construction. As indicated in the recently released ASHRAE UFAD Design Guide, the key to a successful UFAD system starts at the first day of construction in order to avoid issues with leakage in the end, which may be impossible to locate or remedy.

But, the biggest issue I have with energy efficient designs is the apparent lack of validation of the energy calculations created to get owner and code acceptance (and LEED points). There are plenty of examples of buildings using far more energy than was predicted. Some schools are reporting that their expensive schools (at more than twice the cost/unit area of any prior schools in that area) are the highest energy users (again in terms of energy/unit area). I suggest that validation is lacking in many of these claims. An internet search for peer reviewed cases of proven energy savings of innovative designs will show you there isn't much out there. If these designs are so good, I'd expect the internet to be flooded with glowing reports. Sadly, that doesn't seem to be the case. Maybe all the successful building owners and designers are just bashful?

Authored by: Dan Int-Hout, Chief Engineer Krueger