ᐅ Heat load calculation is 10.3 kW; is an air-to-water heat pump with 9.5 kW capacity sufficient?
Created on: 5 Mar 2020 22:09
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hippjoha
Hello everyone,
I just had a brief phone call with our heating engineer. The heating load calculation resulted in a value of 10.3 kW. He would recommend a 9.5 kW air-to-water heat pump (nothing else is possible since drilling, etc., is not allowed), among other reasons because it is eligible for funding through BAFA.
My question now is whether this air-to-water heat pump is adequately sized. In the open-plan living room, we also have a wood stove.
I hope someone here can clarify this for me.
Thank you very much!
Best regards,
Hannes
I just had a brief phone call with our heating engineer. The heating load calculation resulted in a value of 10.3 kW. He would recommend a 9.5 kW air-to-water heat pump (nothing else is possible since drilling, etc., is not allowed), among other reasons because it is eligible for funding through BAFA.
My question now is whether this air-to-water heat pump is adequately sized. In the open-plan living room, we also have a wood stove.
I hope someone here can clarify this for me.
Thank you very much!
Best regards,
Hannes
The CoP value or the annual performance factor is naturally irrelevant when determining whether a heat pump is properly or adequately sized. Nevertheless, certain values must be met (specifically for the location of the planned use) in order to qualify for any possible subsidies.
However, if your heat pump has a nominal capacity of 8.1 kW at 7 degrees Celsius (45°F) outdoor temperature and 35 degrees Celsius (95°F) flow temperature, then the output will likely be significantly lower at -12 degrees Celsius (10°F) outdoor temperature. Therefore, assuming the heating load calculation is correct, this could be a tight fit once it gets really cold, or an expensive situation if the electric heater activates.
However, if your heat pump has a nominal capacity of 8.1 kW at 7 degrees Celsius (45°F) outdoor temperature and 35 degrees Celsius (95°F) flow temperature, then the output will likely be significantly lower at -12 degrees Celsius (10°F) outdoor temperature. Therefore, assuming the heating load calculation is correct, this could be a tight fit once it gets really cold, or an expensive situation if the electric heater activates.
K1300S schrieb:
The CoP value or the seasonal performance factor is naturally completely irrelevant to the question of whether this heat pump is properly or adequately sized. Nevertheless, certain values must be met (specifically for the location of the intended use) in order to qualify for possible subsidies.
However, if your heat pump has a nominal capacity of 8.1 kW at 7 degrees Celsius (45°F) outdoor temperature and 35 degrees Celsius (95°F) supply temperature, then its capacity will likely be significantly lower at -12 degrees Celsius (10°F) outdoor temperature. If the heat load calculation is correct, this could become a tight situation once it gets really cold or an expensive one if the electric backup heater runs. So does that mean the heat pump is too small?
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Daniel-Sp22 Mar 2020 17:20How often do you experience -12°C (10°F)?
And what is the minimum capacity of the heat pump at +7°C (45°F) and at 0°C (32°F)?
And what is the minimum capacity of the heat pump at +7°C (45°F) and at 0°C (32°F)?
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CrazyChris24 Mar 2020 09:04You clearly ended up with the wrong heating installer. He calculates the heating load with the rough rule of area times energy demand plus 20% for hot water. But that’s not how it works.
If you have a heating load of 10 kW for a new build with 252 m² (2713 ft²), you built it incorrectly! Your primary energy demand is also surprisingly high but still within limits. It should be a maximum of 8 kW.
The heat pump you mentioned will very likely no longer qualify for subsidies at the proposed size! The larger the pump, the worse the annual performance factor. Especially the Viessmann air-to-water heat pumps stand out negatively here.
A modulating pump should also be as small as possible and not sized for the lowest outdoor temperature. Just because you have -20°C (–4°F) twice a year doesn’t mean it makes sense to choose a larger pump that can handle those two days. Two days with an additional electric heater (which then only runs for about two hours) are cheaper than running an oversized pump continuously. People sometimes say nonsense about this...
If you have a heating load of 10 kW for a new build with 252 m² (2713 ft²), you built it incorrectly! Your primary energy demand is also surprisingly high but still within limits. It should be a maximum of 8 kW.
The heat pump you mentioned will very likely no longer qualify for subsidies at the proposed size! The larger the pump, the worse the annual performance factor. Especially the Viessmann air-to-water heat pumps stand out negatively here.
A modulating pump should also be as small as possible and not sized for the lowest outdoor temperature. Just because you have -20°C (–4°F) twice a year doesn’t mean it makes sense to choose a larger pump that can handle those two days. Two days with an additional electric heater (which then only runs for about two hours) are cheaper than running an oversized pump continuously. People sometimes say nonsense about this...
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