wireing for a 3.5 ton unit

Old 07-03-02, 11:33 AM
jay k fenwick
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wireing for a 3.5 ton unit

I am wireing my shop I am installing the wireing for a future 3.5 ton a/c heating unit. the run is about 60 feet from my subpanel. will #10 wire be ok or should I use #8? Also the same as above except for a 23-25 amp draw compressor.
Old 07-03-02, 01:48 PM
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wiring for 3.5 ton unit

With out knowing the full load amps(FLA) of the unit it is not possible to size the wire. The rule is amps x 1.25 = wire amps. An example would be if the FLA amps was 24 amps then
24 x 1.25 = 30 amps. #10 cu is good for 30 amps and it would be
the correct size. If the FLA was 25 amps then
25 x 1.25 = 31.25 amps and #10 would not be the correct size. You would need to go to #8 cu.
Old 07-03-02, 05:16 PM
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Look on your name plate for minimum branch circuit ampacity. This will tell you the minimum ampacity required of your branch cricuit conductor.

Look again on your name plate for maximum overcurrent or fuse amps. This will tell you the maximum fuse or breaker allowed to serve your a/c unit.

I once had a heating man ridicule me to my customer saying that if I don't know what size wire is required for a so many ton a/c unit then I shouldn't be an electrician.

What that heating contractor did not know is that each a/c unit has different efficiency ratings and minimum ampacity ratings requirments for the branch circuit conductor and the maximum ampacity allowed on the breaker or fuse. There is no minimum and maximum that fits all a/c units. YOu need to see the name plate info meantioned above to be accurate in conductor and overcurrent device [fuse or breaker] sizing.

Old 07-13-02, 12:30 PM
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Use the #8 wire

It will help prevent any hard start problems that MIGHT occur

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