[Equest-users] eQuest heat pump performance curves

[Daniel Knapp]

I’m not sure I understand why the 39+ capacity curve falls after after 54ºF, but I don’t think that the 39+ and 39- curves have been switched. The 39+ curve goes negative at about 11ºF so it won’t work as a replacement for the 39- curve. Also the 39- curve flattens out as it drops to -13ºF and then starts to rise again. I suspect the curves are intended to be used over an operating range of about -10ºF to 50ºF. Below -10ºF the heat pump chiller shuts off and goes to supplemental resistance heating. Above 54ºF the heat pump chiller is unlikely to have a call for heating? It does seem a bit strange.

Cheers,
Dan

—
Daniel Knapp, PhD, PPhys, LEED® AP O+M
danielk at arborus.ca

Arborus Consulting
Energy Strategies for the Built Environment
www.arborus.ca
76 Chamberlain Avenue 
Ottawa, ON, K1S 1V9 
Phone: (613) 234-7178 ext. 113
Fax: (613) 234-0740




> On Nov 18, 2015, at 11:49 AM, Fernando Varela <fvarela at ind.uned.es> wrote:
> 
> Dear Bill and Jeff:
> 
> The problem arises when you plot for a fix hot water outlet (let's say 113ºF) the whole curve for exterior temperatures (from 9 to 59ºF), using the expression of 39- curve for values till 39ºF and 39+ for the rest of them.
> 
> It shows like this:
>  
> <image.png>
> 
> Shouldn't  COP  increase with higher exterior temperatures for a fixed hot water outlet temperature? It seems even to decay after 54ºF...
> 
> With capacity curves is the same, but in that case it makes more sense.
> 
> Thanks.
> 
> 
> 	
> Fernando Varela Díez
> Dpto. Ingeniería Energética - ETSI Industriales
> Email: fvarela at ind.uned.es
> Tlf: 91 398 6468
> 
> Universidad Nacional de Educación a Distancia (UNED)
> C/ Juan del Rosal, 12. Despacho 2.20
> Ciudad Universitaria, 28040, Madrid
> 
> 
> 
> 2015-11-17 16:03 GMT+01:00 Bishop, Bill <bbishop at pathfinder-ea.com>:
> Fernando,
> 
> The curves look okay to me. I plotted them out for a range of hot water temperatures from 90F to 130F.
> 
> -        I plotted the “…39+” curve for the range of entering dry bulb from 40F to 60F.
> 
> -        I plotted the ”…39-“ curve for the range of Edb from 20F to 38F.
> 
> -        Both curves show decreasing capacity as the heat pump chiller makes hotter water, which makes sense.
> 
> -        Both curves show decreasing capacity with lower outside air condenser temperatures, which makes sense.
> 
> -        The “…39-“ curve shows rapidly decreasing capacity with decreasing condenser temperature below 39F, which makes sense since larger portions of the chiller heat pump heat is needed to defrost the condenser coils.
> 
> -        I’m guessing that the curves are normalized to 110F HWT and 44F Edb.
> 
> I can share an Excel file I used to generate the curves and chart if anybody wants it.
> 
> ~Bill
> 
>  
> 
> <image001.png>
> 
>  
> 
>  
> 
> William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
> 
> Senior Energy Engineer
> 
> <image010.jpg>  <image011.jpg>
> 
>  
> 
> 134 South Fitzhugh Street                 Rochester, NY 14608
> 
> T: (585) 698-1956                        F: (585) 325-6005
> 
> bbishop at pathfinder-ea.com             www.pathfinder-ea.com
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> 
> From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Fernando Varela
> Sent: Tuesday, November 17, 2015 5:04 AM
> To: equest-users at lists.onebuilding.org
> Subject: [Equest-users] eQuest heat pump performance curves
> 
>  
> 
> Dear users:
> 
>  
> 
> I've noticed that eQuest heat pump performance curves:
> 
>  
> 
> ChlrHPAirHeatCap-fHW&39+
> 
> ChlrHPAirHeatCap-fHW&39-
> 
>  
> 
> which refer, respectively, to the temperature capacity factor of the heat pump in normal and defrost mode, seem to be exchanged. This is, ChlrHPAirHeatCap-fHW&39+ curve seems to be the defrost mode curve, and ChlrHPAirHeatCap-fHW&39- the curve regarding to normal mode.
> 
>  
> 
> I've plotted (with fixed condensing temperature) both capacities varying exterior temperature, and observing the results taking the curves in the opposite way as it shoud be (below 39ºF,ChlrHPAirHeatCap-fHW&39+, and ChlrHPAirHeatCap-fHW&39- above 39ºF ), the resulting HP capacity curve seems more like it should be.
> 
>  
> 
> Am I doing something wrong?
> 
>  
> 
> Thank you in advance.
> 
> <image013.jpg>
> 
> Fernando Varela Díez
> Dpto. Ingeniería Energética - ETSI Industriales
> Email: fvarela at ind.uned.es
> Tlf: 91 398 6468
> 
> Universidad Nacional de Educación a Distancia (UNED)
> C/ Juan del Rosal, 12. Despacho 2.20
> Ciudad Universitaria, 28040, Madrid
> 
>  
> 
> 
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