[BLDG-SIM] Heat Pump COP

[Brandon Nichols]

Good point, John -- but there may be an arguably easier way to not
double-count fan energy...following is a reprint from the DOE2
documentation:

 


COOLING-EIR


The Electric Input Ratio (EIR), or 1/(Coefficient of Performance), for
the cooling unit at ARI rated conditions. The program defines EIR to be
the ratio of the electric energy input  to the rated capacity, when both
the energy input and rated capacity are expressed in the same units.
This EIR is at ARI rated conditions, i.e., without correction for
different temperature or part load. 

Note:  If you include fan electric energy consumption in your value of
COOLING-EIR, then you should set SUPPLY-KW/FLOW to zero (and
SUPPLY-STATIC, SUPPLY-EFF and SUPPLY-DELTA-T should be omitted).
Otherwise, the supply fan electrical energy will be double counted. For
commercial systems the default value of COOLING-EIR includes compressor
and outdoor fan energy, but not indoor fan energy. 


HEATING-EIR


Electric Input Ratio, or 1/(heating Coefficient of Performance), for the
heat pump. This EIR is at ARI rated conditions, i.e., without
corrections for temperature or part load. The program-calculated
HEATING-EIR does not include fan power and heat. This keyword is
appropriate only to HP, RESYS, and PTAC systems.  

Mysteriously, the HEATING-EIR documentation makes no mention of the fan
energy double counting issue.  But if you're consistent and use 3.41
divided by the manufacturers published EER for the cooling EIR, the
inverse of the published COP for the heating EIR, and zero-out the
supply fan energy as described in the documentaion ...  then Bob's your
uncle, right? 
FWIW, that's the way we do it...
 
Brandon Nichols, PE, LEED(r) AP
Mechanical
HARGIS ENGINEERS

600 Stewart Street

Suite 1000

Seattle, WA 98101

www.hargis.biz

 

d | 206.436.0400  c | 206.228.8707

o | 206.448.3376  f  | 206.448.4450

 
 

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Fred
Porter
Sent: Friday, October 12, 2007 10:23 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Heat Pump COP


Yes and no. The energy is "removed," but the COP improves because the
fan heat had a COP of 1.0, and is included in the rated gross kW in and
Btuh out. I think the T24 ACM may have a "method" or formula.



  _____  

From: Aulbach, John
Sent: Thu, 10/11/2007 3:25pm
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Heat Pump COP


Folks:
 
In eQuest, the Energy Input Ratio (EIR) can be derived from EER or COP
given for a unit or from a Standard. To correctly model such a unit, one
must subtract the fan energy for the unit to obtain the EER (EIR) of the
compressor only. This improves the input from, say, a COP of 12.3 to 15.
 
What about in the case of the heat pump heating COP? Must one subtract
out the fan energy here as well, thus "worsening" the COP for the
heating side?
 
I cannot find anything written on this subject.
 
Thanks.
 
John R. Aulbach, PE, CEM
Project Manager
Nexant, Inc.
100 North Barranca, Suite 820
West Covina, CA 91791 USA
Phone: 626-430-9054
Fax: 626-430-9060
email: jaulbach at nexant.com
 
 
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