1. Junior Member
Join Date
Dec 2003
Posts
16

## Tons to amps

Is there a way to calculate an air conditioning load if all you have is the size of the unit in tons? Applied voltage is also known. 208v 1 phase - 4 ton unit. This is a hermetically sealed compressor.

2. Moderator
Join Date
Jun 2003
Posts
6,021

## Re: Tons to amps

I usually use 1.5 KVA per ton, for AC units in the 2-5 ton range, but it can vary a lot.

Steve

3. ## Re: Tons to amps

1 Ton of refrigerant =3.5 KVA. So if you 4 tons, you're looking @ 14 KVA or 14,000 watts. I=P/E. 14,000/208=67.3 amps

4. ## Re: Tons to amps

I usually use 1.5 KVA per ton, for AC units in the 2-5 ton range, but it can vary a lot.
1 Ton of refrigerant =3.5 KVA

5. Senior Member
Join Date
Nov 2004
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3,172

## Re: Tons to amps

I have measured my own, very old, 3-ton unit at 19A @ 240V. That works out to 1.5KVA/ton. The breakers are 30A. 3.5KVA/ton sounds much too high for a modern AC unit.

6. ## Re: Tons to amps

I used OC Conversion Pro: where 1 ton of refrigeration = 3,516.85284 volt ampere or 3.5 KVA.

"I have measured my own, very old, 3-ton unit at 19A @ 240V. That works out to 1.5KVA/ton. The breakers are 30A. 3.5KVA/ton sounds much too high for a modern AC unit."

Now that I think about it, That does sound kind of high, I may have done something wrong in my calculation. :confused:

7. ## Re: Tons to amps

So what do you do when you have to design for an essentially unknown load? Go huge?

Do you try to go as small as you can to get the bid and hope you don't shoot yourself in the foot?

The whole idea of doing this backwards seems unprofessional to me. (No offence intended towards you garyfitzgerald). I see this sort of dilema a lot.

8. Senior Member
Join Date
Sep 2004
Posts
388

## Re: Tons to amps

I've never done a lot of research on it. I do not deal much with compressor/condenser units of this size.

But a general rule-of-thumb that I've used for 1-phase, 240V. units in the appx. 2 - 5 ton range is 1440VA per ton.
This is close to steve66 1.5KVA.

[ February 25, 2005, 08:32 PM: Message edited by: kiloamp7 ]

9. Senior Member
Join Date
Nov 2004
Posts
3,172

## Re: Tons to amps

A little background is in order here. About 1 KW is needed to drive a 1 hp motor,and about 1 hp is needed to drive a 1 ton AC compressor. Throw in some PF, and you have 1.5KVA/ton. This number may be a bit high for modern AC units though.

10. ## Re: Tons to amps

Another way

One ton of frig.=12000 BTU
1 watt=3.412 BTU

4 tons x 12,000=48,000 BTU

48,000/3.412=14,068 watts

14,068/208 volts=67.63 amps.

Ronald

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