How to get HVAC heat pump load estimates?

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liam913

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Location
Boston
Occupation
Electrical Engineer
Mechanical engineer sent me cutsheets for some outdoor heat pumps that give me an MCA and MOCP. I would like to get an as accurate as possible load in VA. I have seen multiple people say to use the MCA here but this is a large scale project where there are multiple in use.

How do I get the FLA for the units? I don't want to overestimate.
 
liam913 said:
Mechanical engineer sent me cutsheets for some outdoor heat pumps that give me an MCA and MOCP. I would like to get an as accurate as possible load in VA. I have seen multiple people say to use the MCA here but this is a large scale project where there are multiple in use.

How do I get the FLA for the units? I don't want to overestimate.
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Ask mechanical who the sales rep is.
 
There should be RLA on the cut sheet. Likely only for the compressor so you would need to add FLA of fans or any other loads it may have.

RLA is basically it's max design load sort of like FLA on a motor. Most the time they don't draw RLA but in extreme conditions they will draw more current than usual. Same compressor unit may have different current in a different installation, that is due to differences in those installations. The load on the compressor will vary depending on how much heat the system is moving, differences in ducting, plugged coils, etc. also will have an impact.
 
The best way is to do a Manual J load calculation. Anything else is mostly a guess. You need correct info like home size, insulation, windows, and local weather. Most HVAC contractors use software for this. If you just want a basic understanding, this page about the HVAC industry is helpful, but you shouldn’t size a heat pump without a proper load calculation.
 
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