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!