Tuesday, March 12, 2013

Canada in Winter

I went to Ottawa in February. I’d forgotten what winter in the cold North was all about, but it all came back in a rush.

I spoke to the Ottawa ASHRAE chapter with my latest presentation, titled “What A (Building) Load”. I’ve been working on this for a while, as my “Methods of Effective Room Air Distribution” talk is a couple of years old and was published in November and December in the ASHRAE Journal.

Having been on the project review committee of the ASHRAE research project 1515, which was a thorough study of a couple buildings in California, where occupant response, equipment operation and energy use were all mapped, I have a pretty good idea of what was in the final report, presented in Dallas last month. The building loads were all far below what most engineers design for, and required setting the minimums on the VAV boxes at 10% of maximum to keep from going into reheat every afternoon. What was most interesting is that there were minimal complaints at the low air flows, and occupants were generally satisfied at 0.2 cfm/sf. This confirms the idea that there is no minimum air speed for comfort, which has been in the ASHRAE Comfort Standard for some time.

This leads to a conclusion that using a series fan terminal with an ECM motor and varying the air flow rate to as low as possible offers a very energy efficient way to provide HVAC to a commercial office space. It can be even better if a sensible cooling coil is placed at the inlet of the unit. This concept was utilized at the Pentagon in its most recent upgrade and is being used in a number of buildings around the country.

I described this concept to a design build contractor in Ottawa, and when he realized that one could actually eliminate the air handler (using only a DOAS unit) he is going to try this on a couple of designs.

I also did some webinars a couple weeks ago on “the basics of air distribution” and maxed out our number of available connections. I guess going back to the basics is something we have to do once in a while.

Authored by: Dan Int-Hout, Chief Engineer Krueger