[Bldg-sim] 90.1 - leaving air temperature (DX cooling / Economizer)

[David Berty]

Leaving air is indeed the air stream leaving the cooling coil.


In my experience, most OA economizers are not set this aggressively in the field because of problems with cold spots.


David Berty P.E.
Baseline Energy Consulting
317.220.9272



________________________________
From: Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> on behalf of Jim Dirkes <jim at buildingperformanceteam.com>
Sent: Monday, November 23, 2015 4:15 PM
To: Julien.Dutel at mern.gouv.qc.ca
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] 90.1 - leaving air temperature (DX cooling / Economizer)

Without looking at the 90.1 definitions pages (though I recommend that), the meaning should be the temperature leaving the cooling coil, since that is what might freeze.

2015-11-23 16:11 GMT-05:00 <Julien.Dutel at mern.gouv.qc.ca<mailto:Julien.Dutel at mern.gouv.qc.ca>>:
Hello,

Section 6.5.1.3 of 90.1-2013, requires that the "outdoor air damper does not begin to close to prevent coil freezing due to minimum compressor run time until the leaving air temperature is less than 45°F"

1) I'm not an expert with refrigeration system, and I want make sure that I have the good interpretation of what is the "leaving air" .
A) "Leaving air" is the mixed air (outside air + return air) that leaves the evaporator coil of a DX cooling system, so it's pretty much equivalent to the supply air.
B) "Leaving air" is the air leaving the outdoor air damper, so it's equivalent to the outside air.

2) If the answer is A, based on your experience in the field, have you notice any comfort problem by supplying air at 45°F when the unit setpoint is typically at 55°F ?

Many thanks,

Julien Dutel, ing., CEM, CMVP.
Direction des secteurs résidentiel, institutionnel et des affaires
Bureau de l'efficacité et de l'innovation énergétiques
Ministère des Ressources naturelles
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James V Dirkes II, PE, BEMP, LEED AP
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The Building Performance Team Inc.
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