[Bldg-sim] ASHRAE 90.1-2004 Packaged Terminal Heat Pump Efficiencies
ldegelman at suddenlink.net
Tue Dec 1 08:52:02 PST 2009
You are correct to use Watts for the SI equation. The counterpart equation for the PTHP (cooling mode, new construction) in the IP version is [12.3 - (0.213 x Cap/1000)], but is expressed as EER (not COP.) COP's are expressed for heating mode as [3.2 - (0.026 x Cap/1000)]. That lower coefficient (0.026) softens the Cap/1000 value, when Cap is in Btu/h.
Larry O. Degelman, P.E.
Professor Emeritus of Architecture
Texas A&M University
From: Dan Jestico
Sent: Tuesday, December 01, 2009 10:34 AM
To: Bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] ASHRAE 90.1-2004 Packaged Terminal Heat Pump Efficiencies
We're trying to obtain the minimum CoP for a Packaged Terminal Heat Pump in cooling mode for a new construction using table 6.8.1D in ASHRAE 90.1-2004 (SI edition) and the formula is proving to be somewhat confusing. In the SI edition it is described as
[3.60 - (0.213 x Cap/1000)]
Is this the same equation as listed in the imperial edition of 90.1-2004? If the max. unit capacity of 4.4kW is converted to Btu/hr (approx 15024 Btu/hr, as per note c) and input to the formula, the minimum CoP is only 0.4, which seems very low. However, if I use the value in Watts in the equation, the minimum CoP comes out as a much more reasonable 2.66.
I can't seem to find any addenda on ASHRAE's website or additional guidance on this matter and would very much appreciate any guidance you can provide.
Many thanks for your help.
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