AC TONS TO CURRENT

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florida-sparkey

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Need to do an energy calc for the PC on a residence. They want both tons and KW. I have the tons (4) but that is all the AC guy gave up. I remember a basic translation existed but its been a long time. Voltage is 240 Nominal. I can guess and throw down 30Amps but that's not any fun. Any help?
 
infinity

infinity

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It can vary depending on the efficiency of the system components. I would just look up a few random 4 ton unit spec's and take it from there.
 
tw1156

tw1156

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These are "loose" values that I have used in the past:

1kVA per ton can be a rough start and we'll use it for quick calcs when we have no additional information and are trying to anticipate service size to a building. I'm unsure if this is true for residential though.

~350 - 400sqft / ton on average, but this varies by space and location.
 
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florida-sparkey

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I have also looked up a few and they seem to be around 17 RLA, FANS 1.2 FLA. This is close to what most have suggested so going to use 18.5A / 4.4KW and call it Friday!
Thanks!
 
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Ingenieur

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florida-sparkey

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Ingenieur said:
that is ~a 2 ton trane unit
https://www.trane.com/content/dam/T...stems-1-1-2-to-5-tons/22-1864-03_01012013.pdf
Click to expand...

Thanks for the help. I really appreciate it.

I think you are looking at min circuit ampacity? Unless I am misreading it, the 4 ton unit on your sheet has 21.2 RLA and 1 FLA FAN. A little larger but I have found Trane to do that. If I hadn't already done the clac and sent it I would of used your load. Its the largest I have seen of the 5 I looked at. In any case, +-5A is not a big deal in this calc.
 
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florida-sparkey

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Ingenieur said:
that is a direct conversion without unit eff considered

in the US htg/clg calcs are done in btu's and that is how units are rated
12000 btu = 1 ton clg capacity

units are elec/mech overall eff ~50%
so you can use 1/2 of the calculator kw value
but obviously best to have specific unit data or at least similar units
Click to expand...

Thanks, I was wondering how it got to 60A. Even half is higher than the units you posted links to. I think the "pull a few random data sheets" is the most realistic so far.
 
gadfly56

gadfly56

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Ingenieur said:
that is a direct conversion without unit eff considered

in the US htg/clg calcs are done in btu's and that is how units are rated
12000 btu = 1 ton clg capacity


calc 4 ton ~ 14 kw or 58 a at 240/1
actual numbers 28-30 a or 7 kw
Click to expand...

Are you assuming a COP of 2 or better?
 
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Ingenieur

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al hildenbrand said:
Power equals volts times amps. Solve for amps. A = W / V = 14,000 / 240 = 58.33333 Amps.
Click to expand...

cop = coef of performance
bssically output kw/input kw
it varies might be ss low as 1 if very hot outside > 100 f
and as high as 3-4 if inside temp ~ outside temp 70 F
the eff varies with the delta oat vs desired inside temp

so if the unit has a cop of 2
4 tons or 14 kw of clg can be done with 7 kw of elec
7000/240 = 29 a
 
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