Friday, April 13, 2018

What A Long Strange Trip It Has Been

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