Wednesday, September 19, 2012

My Findings in Washington D.C

I spent the last few days in our nation’s capitol. In the schedule were a couple of speaking engagements as well as a few sales calls with our Terminal Unit Product Manager.

Interestingly, Washington D.C. has a number of very “progressive” Mechanical Engineering firms – probably more than any other city I have visited. All are very interested in “pushing the envelope” in air distribution designs and are, in one way or another, using a series fan powered VAV terminal unit as the basis of their designs, always with an ECM motor. Most are using a “Chilled Box”, or DOAS fan terminal unit, as it is sometimes called, which is a series fan box with a sensible cooling coil on the induction port. We have a white paper on this technology on the Krueger website. (

The DOAS terminal unit was the subject of the Washington D.C. chapter ASHRAE dinner talk, presented by Southland Industries. They recently finished a retrofit of the Pentagon using this technology. The talk was an excellent discussion of both the development of this strategy and the control options possible. They mentioned the beginnings of the concept and even the SSA Payment Centers with which I was involved in the ‘70’s, a precursor to this concept. My first exposure to the concept dates back to 1991. Similar to Carrier’s 36 series induction units, first installed in 1948, both the chilled beam and the DOAS fan terminal units use similar technology by combining non-condensating cooling coils and conditioned primary air to handle the sensible load in the space. That product was one of the many products I supported as terminal engineering manager back then. It is gratifying to see the excitement we observed on this technology at the many engineering firms we deal with in the D.C. area. In fact, one participant during the Q&A period stated “Since this is obviously the way we are going to be doing things in the future.”

I couldn’t agree more. The use of variable flow ECM motor technology, tied to a sensible cooling coil and a low temperature DOAS system, will likely be the most cost effective way to provide load management and ventilation to many types of spaces for some time to come.

Authored by: Dan Int-Hout, Chief Engineer Krueger