Hello Everyone:
I am working in an office building project located in Galicia (Spain). We are carrying out the selection process of the heat pump for the air conditioning of the building. According to ANSI/ASHRAE/IESNA 90.1-2007, this heat pump (>40 kW) must comply the following minimum efficiency requirements:
COP (8.3 ºC db / 6.1 ºC wb): 3.2 (as of 1/1/2010)
COP (-8.3 ºC db / -9.4 ºC wb): 2.0
The heat pump we are evaluating has a COP of 3.5 (8.3 ºC db / 6.1 ºC wb). However, the manufacturer of the heat pump does not have the COP value at -8.3 ºC. They send us a letter explaining that this heat pump doesn’t operate under -7 ºC.
We have analyzed the historic minimum site temperatures, and the minimum recorded temperature is -2.7 ºC, so the heat pump would never work under -7 ºC. Additionally, the manufacturer has given us the COP values at various temperatures. With these data, we obtained an equation that relates COP to temperature. The coefficient of determination (R2) of this equation is 1, and our estimated COP with this equation at -8.3 ºC is 2.2 (above the minimum ASHRAE value). This is the efficiency value which would have the machine assuming it could work at -8.3 ºC.
Thus, could we achieve the ASHRAE requirements compliance taking into account these considerations?
Thanks in advance!
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
June 28, 2017 - 9:51 am
Sure sounds like it to me. You have done an admirable job of due diligence. Provide this explanation to the reviewer when submitting.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
June 28, 2017 - 10:38 am
Looks like you're using 90.1-2010?
I was looking at this, since it seemed wrong. Turns out Table 6.8.1B lists, for the heating mode, first the COP for heating and then the COP for cooling underneith it (because they can do both at the same time these days). E.g.
COP (8.3 ºC db / 6.1 ºC wb): 3.2 (as of 1/1/2010)
COP (-8.3 ºC db / -9.4 ºC wb): 2.0
However, there is a typo for the >=40 kW air cooled machine (heating mode). If you flip to p14 at the back of the 2012 Addenda, you notice that it should be
COP (-8.3 ºC db / -9.4 ºC wb): 2.05
and not
COP (8.3 ºC db / -9.4 ºC wb): 2.05
...but it looks like you got that.
That being said, if your unit cannot cool whilst in heating mode, then that COP requirement is void, right?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
June 28, 2017 - 11:19 am
The minimum efficiency requirements are void only if the equipment in question is not addressed by the standard.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
June 29, 2017 - 3:56 am
So how would you evaluate a heatpump that only heats? Is there an extra item for it?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
June 29, 2017 - 9:21 am
In 6.8.1B there is a referenced testing standard associated with the minimum efficiency for each row. In order to determine if a particular piece of equipment is covered under the testing protocol you have to go into that testing standard to see specifically what equipment is covered.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
June 29, 2017 - 9:36 am
In 6.8.1B there is a referenced testing standard associated with the minimum efficiency for each row. In order to determine if a particular piece of equipment is covered under the testing protocol you have to go into that testing standard to see specifically what equipment is covered.
Jorge Mato Rial
Electrical EngineerINSTRA Engineers
July 5, 2017 - 2:53 am
Thanks for your comments!
We are evaluating several machines. If we finally choose this one, we will provide to the reviewer these explanation.
Best regards