wiring amperage?

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  #1  
Old 12-16-12, 10:24 PM
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wiring amperage?

Hello there,
I have an American Standard air handler, which has aluminum wiring I'd like to change out for copper. The breaker in the box outside the house is 100 amp dual pole, which then runs the aluminum wire into the air handler, which then splits off to a 60 and 30 amp breaker.. Can someone tell me what size of wire I should be using? 100 amp wire looks too big. I'm assuming both 30 amp and 60 amp don't run together at the same time and that I'm meant to have 60 amp wire running, but I'm no expert.
 
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Old 12-16-12, 11:59 PM
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I'm assuming both 30 amp and 60 amp don't run together at the same time and that I'm meant to have 60 amp wire running,...
That would be an erroneous assumption. You need either #3 or #2 copper conductors.
 
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Old 12-17-12, 03:45 PM
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no, both will run at the same time when all your aux heat strips are on. We can't tell you what size wire is needed without knowing the length of the run. You should run wiring to each breaker.
 
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Old 12-17-12, 07:33 PM
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The run would be about 20 to 30 feet. I'd have to go measure to be more accurate. Are you saying I should have a breaker outside for each breaker inside the air handler? And run 60 and 30 amp wires to both respectively? I don't think I have aux heater elements. There are 3 of them which add up to 15kw I think...How do you know if they are all run at the same time? I should probably take some pictures of the name plates and post. The one thing the install guide does actually say is don't use any other conducter other than copper....Aluminum was used back in the day so for whatever reason they ignored the guidelines then.

There's also the compressor outside, which is run aluminum as well. And that is about 40 to 50 feet. I'm just trying to get one thing at a time done. So I'd like to get the airhandler out of the way first..And for some odd reason these appliances are the only things that are run on aluminum wiring in the entire house everything else is copper.
 
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Old 12-17-12, 08:27 PM
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if you have 15kw. then that is (3) 5 kw strip heaters. Depending on how the low voltage was wired they will and should all run at the same time at some point. Ideally they would be staged on. I would use 10 AWG for the 30A circuit and 6 AWG for the 60A circuit.
 

Last edited by hvactechfw; 12-17-12 at 08:47 PM.
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