[Bldg-sim] ASHRAE 90.1-2004 Packaged Terminal Heat Pump Efficiencies

Larry Degelman ldegelman at suddenlink.net
Tue Dec 1 08:52:02 PST 2009


Hello Dan,

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.

LOD
===========================
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


Afternoon all,

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.

Dan.

DAN JESTICO 

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