Thursday, June 30, 2011

Montreal ASHRAE Meeting Updates

Well, another ASHRAE meeting is behind us. There are a few interesting items to report:

Standard 55 (Thermal Comfort) is being made to be “more mandatory”. As it is referenced in many codes, there has been a concern that it is a bit wishy washy in its requirements. To clear up the concerns, changes are proposed that will make it clear that Standard 55 is intended to standardize how one calculates thermal comfort, not which conditions will be required. It may help the code guys, but will likely still be misinterpreted.

A study ongoing through the Thermal Comfort Technical Committee (TC 2.1) is showing, yet again, that buildings are operating at far lower loads than they are designed for. In many cases, VAV systems are showing satisfactory performance at less than 0.3 cfm/sq. ft. Airflows greater than that are causing systems to run in reheat in interior/cooling zones. This is further evidence that part load operation is the predominant condition and that we need to be designing for that eventuality.

The results of the Texas A&M study on Series vs. Parallel / ECM vs. PSC motor study has been donated to both ASHRAE and AHRI at the summer meeting. It is hoped (indeed expected) that these results (partly funded by Krueger and two other manufacturers) will result in a rewrite of Appendix G of 90.1 which currently favors Parallel boxes, to the exclusion of Series flow types.

AHRI’s ACDD section, which covers VAV terminals, has updated their Operations Manual. We will be seeing a change in everyone’s discharge sound performance in the next year to account for end reflection in the reverb room. Other standards take this phenomenon into consideration, but VAV boxes, which have been using test methods developed before ASHRAE, had a full understanding of End Reflection, do not. The result will be between 3 to 7 NC increase, depending on unit discharge duct size, in reported, and certified, discharge sound levels. The units won’t be any louder, but the sound data will increase. Typically, discharge sound is seldom critical, especially when there is lined duct present between the box and the diffuser.

TRG7 / UFAD which is a committee rewriting the Underfloor design manual (no longer available from ASHRAE) has uploaded all the first draft documents to a website where committee members can propose revisions and review changes to the entire draft. We should be able to have an approved document to turn over to ASHRAE (which will do an independent review) after the Chicago meeting. This is the first design guide written by a technical committee, not an independent contractor. Fortunately, I am rolling off as chair of this committee after this meeting and hand the reigns over to the very capable Jim Mergerson of Burns and McDonald of Kansas City, who has many successful UFAD projects to his credit.

I’ll be glad to get back to the USA, where at least I can read signs directing me where things are!

Authored by: Dan Int-Hout, Chief Engineer Krueger