new 220v installation

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  #1  
Old 04-14-07, 09:15 PM
ben
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new 220v installation

Hi,
I need to wire for a new central AC installation. The outside compressor and the air handler both uses 220V. The compressor needs 30 amp and the air handler needs 5 amp.

I wanted to use an existing 220 40 amp line that is not currently being used
for the compressor. However the 4 feet wire from the service box to the unit is a #10 wire. Another words, from the service panel to the service shut off box uses a #8 with a 40 amp beaker and from the service shut off box to the compressor unit uses a #10 wire. Is this ok?

For the air handler inside(attic) I am planning on using a #12 wire with a 15 amp 2 pole breaker. Someone has told me to use a #12 wire instead of #14 because of the higher heat from 220. And also I am not able to find #14 wire with 1 red, 1 black and 1grn(ground). All I can find is 1 black, 1 white and 1 ground. Is this ok to use? However I found #12 with 1 red, 1 black , and 1 white(white will be used for ground)

Is what I am doing here ok? Please advice Thanks in advance
 
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Old 04-14-07, 09:49 PM
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You can use that older circuit, but replace the breaker with a 30A, since the compressor disconnect to compressor wiring is #10, and it only needed a 30A circuit anyway.

#14 is fine for the air handler. There is no extra "heat" in a 240V circuit of the same amperage. But if it's easier to find a 20A breaker, then make sure you use #12 wire.

Did the compressor specify a 30A breaker? Or did it say that it draws 30A? Those mean different things. Is the #10 wire in question part of the factory assembly?

If you are using a preassembled cable, like Romex, you can run 240V by using the black and white wires. Please recolor the white wire wherever it is visible by using a marker or tape along its length, any color except white, gray, or green. It can even be a second black. If you go with that #12, recolor the white to be a green.
 
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Old 04-15-07, 06:09 AM
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Note that you need a 120 volt circuit nearby as part of the installation.
 
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Old 04-15-07, 05:52 PM
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Thanks for the help.

The compressor specify a minimum 30 amp and maximum 35 amp breaker. should I use a 30 or 40 amp breaker? I could not find a 35 amp breaker. The #10 wire is not factory assembly. The AC supply house sold me this #10 wire with liquid tite conduit and it is only 4 feet long. Will this be ok with 40 amp?

If I use a 12 amp for the air handler, will it cause any problem for the air handler's motor? Since it only require 5 amp max.
Is not #14 wire too thin for 220v?

Is 120 outlet near outside unit required by the code ?
 

Last edited by ben; 04-15-07 at 06:08 PM.
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Old 04-15-07, 06:00 PM
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If the directions call for a 30 or 35 amp breaker why would you use a 40 amp one? Use a 30 amp breaker.

Wire size (12 gage, 14 gage, 10 gage, etc.) is based on is based on current, not voltage.

For the handler use a 15 amp breaker and 14 gage or 12 gage wire; or use a 20 amp breaker with 12 gage wire.

For the 120 volt convenience receptacle you need use either a 15 circuit or a 20 amp circuit.
 
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Old 04-15-07, 06:42 PM
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Use the 30A breaker for the compressor. You need it to protect that #10 wire.

I thought we already settled that #14 is fine for a 240V load, as long as it's protected by a 15A breaker.

Yes, the 120V standard household receptacle is required by the Code for using power tools while servicing the equipment. The equipment itself doesn't need it. It's up to you if you want to (or have to) follow the Code in this respect.
 
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Old 04-15-07, 07:10 PM
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Thanks again for all the help.

Couple of things that I forgot to ask.
I need to install a service switch for the air handler. What should I use in this case? 2 pole 125V switch is ok for this case?

Also, do you happened to know whats the height from the ground up that the service shutoff box for the compressor should be installed?
 
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Old 04-15-07, 07:40 PM
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The switch would have to be DPST (double-pole, single-throw) and rated at least 250V.
 
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Old 04-15-07, 07:42 PM
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Don;t think there is a minimum height. Usually these boxes are 2-4 ft. off the ground.
 
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Old 04-16-07, 01:44 PM
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Hello All,

As planned, I am running the #8 with a 30 amp breaker (to reuse the existing 40amp unused line) to the outside unit. However as I opened the electrical box on the unit, it is using #12 gage wire (factory assembled). Will this be a problem? Please advice thanks in advance
 
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Old 04-16-07, 02:21 PM
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Nevermind; redundant post.
 
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Old 04-17-07, 05:26 AM
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Question

What do you mean "redundant post"
 
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Old 04-17-07, 07:44 AM
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I accidentally posted the same information that has already been provided by others before me.
 
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Old 04-17-07, 01:45 PM
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"As planned, I am running the #8 with a 30 amp breaker (to reuse the existing 40amp unused line) to the outside unit. However as I opened the electrical box on the unit, it is using #12 gage wire (factory assembled). Will this be a problem? Please advice thanks in advance"



The wiring size leaving the breaker panel to the compressor has nothing to do with the internal wiring of the unit. If that was what you were asking?
 
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