Thursday, May 25, 2017

High Performance Air Systems

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!

Wednesday, April 5, 2017

A Look Back

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.     

Thursday, March 30, 2017

Getting Caught Up

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.

Monday, July 25, 2016

NW Code Requirements

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

Tuesday, July 12, 2016

ADPI and Standard 55

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


Wednesday, November 4, 2015

CO2 is a problem?

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.

Friday, October 2, 2015

Underfloor Products

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