No nameplate

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OK Sparky 93

Senior Member
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Iridea14Strat
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Electrician
I have the taste of providing power to a relocated 3 phase A/C. I have been told that it is a 5 ton. The nameplate might as well not be there. How would a guy know or find out the minimum amps?
 
The ton rating is pretty useless for determining the current draw because of different SEER ratings. The most accurate way would be to hook it up and run it then take current readings on the individual components.
 
OK Sparky 93 said:
I have the taste of providing power to a relocated 3 phase A/C. I have been told that it is a 5 ton. The nameplate might as well not be there. How would a guy know or find out the minimum amps?
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Can you not simply duplicate what is supplying it now?
 
infinity said:
The ton rating is pretty useless for determining the current draw because of different SEER ratings. The most accurate way would be to hook it up and run it then take current readings on the individual components.
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I always hate when a builder or GC says It will be “X tons”. Then I tell him tons means nothing to an electrician.
 
hillbilly1 said:
I always hate when a builder or GC says It will be “X tons”. Then I tell him tons means nothing to an electrician.
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Exactly! And your the only trade that has been the on the job. The job is commercial, adding a living quarters. The owner says no 3 phase needed. He had this used unit in storage. A/C guy shows up and says yeah it’s a 3 phase 5ton.
Now that I already have the panel mounted and my homies running
 
OK Sparky 93 said:
Exactly! And your the only trade that has been the on the job. The job is commercial, adding a living quarters. The owner says no 3 phase needed. He had this used unit in storage. A/C guy shows up and says yeah it’s a 3 phase 5ton.
Now that I already have the panel mounted and my homies running. Enough of my rant.
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RTU are about 4 amps/ton on 240v half of that for 480

If you open up the panel on the unit and scrounge around they usually have the model and serial # inside as well. At least Carrier always doesYour have to search a little.

If not wort case is you add up loads compressor, indoor blower and condenser fans etc. Don't include any heat. If it has electric heat then you have to calculate the heat amps.

Take the larger of the AC or Heat load then add 25% of the largest load (compressor) or (electric heat) That will give you the MCA
 
If it is 5 ton [ice] air conditioning then it produces 60000 Btu/h [17.58 kW[=23.6 HP]
However, the air conditioning pump draws only 8.5 hp [6 kW].
If the p.f.=0.85 the kVA=6/0.85=7.At 480 V [USA] I=7000/SQRT(3)/480=8.5 A
 
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