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Estimating Heat Pump Output (BTU/h)

Air Source Heat Pumps (ASHPs)

Last Post by neilrobertson 2 years ago

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neilrobertson

(@neilrobertson)

New Member Member

Joined: 2 years ago

Posts: 3

Topic starter 01/06/2024 8:20 pm [#1566]

My centrally-ducted heat pump is a variable-speed Bryant 284ANV048. This brand is marketed in the U.S. and is made by Carrier. It has a fancy thermostat with a screen called "Equipment operating status". This screen reports something called "HP var", which is reported as a percent, and can vary between approximately 30% and 100%. My question: is there a way to estimate the heat output in BTU/h from this HP var parameter? Note that I have the heating capacity curves for the heat pump.

thanks,

Neil

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Derek M

(@derek-m)

Illustrious Member Member

Joined: 6 years ago

Posts: 4425

02/06/2024 9:38 pm

Hi Neil,

I presume that you live in the USA and have what we in the UK would call an Air to Air (A2A) heating system, in that when in heating mode it takes thermal energy from the outside air and uses this thermal energy to heat the indoor air.

I assume that the HP Var is an indication of how fast the heat pump compressor is operating, which often indicates how hard it is working. I doubt that you would be able to ascertain the actual thermal energy output from the HP Var value either in BTU's or kW's, since this will vary with the size of the heat pump and the operating conditions.

I would suggest that you contact the manufacturer and ask if there is a way to obtain the information that you seek.

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neilrobertson

(@neilrobertson)

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Joined: 2 years ago

Posts: 3

Topic starter 02/06/2024 10:43 pm

@derek-m

Thanks Derek. Note I do have the capacity vs. temp curve for the heat pump. I have not had much luck with the manufacturer. Here, the manufacturers seem always to direct you to the local contractors/installers -- who are very polite but not of any help. I wish they were rude and useful!

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Derek M

(@derek-m)

Illustrious Member Member

Joined: 6 years ago

Posts: 4425

02/06/2024 11:05 pm

@neilrobertson

The majority of heat pumps in the UK are Air to Water (A2W), which makes quantifying the thermal energy output easier by installing a thermal energy output meter. In basic terms it measures the water flow rate passing through the heat pump, measures the temperature of the water going into the heat pump and the temperature of the water coming out of the heat pump. It is therefore only a matter of determining the temperature increase of the water and the flow rate and applying the Specific Heating Capacity for water.

In theory it should be possible to do the same with an A2A heat pump, provided that you can measure the air flow rate and In and Out temperatures with a sufficient degree of accuracy.

I would be interested to see the capacity vs. temp curve that you mention.

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