How to find peak wattage of AC unit?

Burnrate

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Apr 20, 2022
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Is there a way to find out the surge of your home AC?

It is understanding that my air handler and condenser will just between 3800-4200 watts while running (based on the seer rating and tonnage). I've seen things state the surge will be anywhere between 2x two 5x of that. 8 kw to 20 kw is a huge range and I can't measure it unfortunately.

I have a 4tec trane 4ton unit. (4tec3f48b1000aa is the handler, 4twr3048a1000aa is the compressor)

The only thing I saw was an lra of 134 on the compressor which would mean 32 kw surge which just seems nuts. Is that for real?
 

acdoctor

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Oct 5, 2020
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Yes it is for real. I see it daily. If a compressor won’t start because of baring issues or other problems. They will exceed 100 amps for a second or three before the breaker trips or the internal thermal trips. Their are amp meters out there that can capture the start inrush.
 

RCinFLA

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Many Trane's use Copeland scroll compressors. They have a very high startup surge current. My 4 ton Trane compressor as factory delivered has 195A for 400 milliseconds @240vac startup surge current.

I installed a MicroAir EasyStart 368 softstart/booster cap startup unit and brought the 195 amps down to 77 amps.
 

Burnrate

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Apr 20, 2022
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41
Many Trane's use Copeland scroll compressors. They have a very high startup surge current. My 4 ton Trane compressor as factory delivered has 195A for 400 milliseconds @240vac startup surge current.

I installed a MicroAir EasyStart 368 softstart/booster cap startup unit and brought the 195 amps down to 77 amps.
Awesome! I just saw that:

One review said it brought theirs from 134 to 33. The system I want to setup should be good as long as it stays below 50.

195 amps is crazy.
 

RCinFLA

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SecureStart's chart. I think this is 3.5 ton Copeland scroll compressor. Scroll compressors have a large heavy counter weight to spin up for their 'wobulator' scroll counterbalance and high initial mechanical load during startup.

Scroll compressors are like the Mazda Wankel engine of compressors, but they are pretty rugged.

I'd take any manf. supplied examples with a grain of salt.

Refrigerant charging variance, ambient temp, and line voltage varies results.

During the five training cycles on the EasyStart, the lowest startup current was 68 amps but it sounded like it was dangerously close to stalling out. The training computer justly selected the next higher level which was 77 amps for my unit. I have been using it for about 2 1/2 years. It is much easier on the contactor relay contacts wear.

SecureStart chart.gif
 
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