Central A/C wiring

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  #1  
Old 04-07-14, 05:44 PM
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Central A/C wiring

I am getting central air conditioning installed within the next couple of weeks and I need to run the electric for both the Air Handler and the A/C Compressor.

Unfortunately the installer does not do the electric so I will be running the lines and having an electrician come in to terminate.

I will be getting a 2 zone system installed so I will have to air handlers up in my attic and to A/C compressors outside. I currently have a 10-3 wire ran for 1 AC compressor outside. I still need to run another line for the other compressor, I will run 12-3 since it will be for a smaller unit.

My main question is, what kind of wire should I run to the air handlers in the attic? Are they standard 120V or are they 240V? Should I run 12-3 or 12-2 for both air handlers?
 
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Old 04-07-14, 06:04 PM
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We need more information to answer your questions.

First of all, where in NY are you? All codes are local and there are different requirements for wiring methods in "the city" than in the rest of the state.

I currently have a 10-3 wire ran for 1 AC compressor outside. I still need to run another line for the other compressor, I will run 12-3 since it will be for a smaller unit.

My main question is, what kind of wire should I run to the air handlers in the attic? Are they standard 120V or are they 240V? Should I run 12-3 or 12-2 for both air handlers?
What is the power drew of each condensing unit and each air handler? If you don't have them at home and unpacked yet, just look up the information online. Or you can post a link to the information, or the specific make and model of each.
 
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Old 04-07-14, 06:13 PM
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I am in West Islip Long Island which is in the Town of Islip.

I do not know the exact modem numbers of the equipment yet and I know they all vary. I am going with the following series:

http://cdn.globalimageserver.com/fet...ication-sheets
http://cdn.globalimageserver.com/fet...ication-sheets

Not sure if that will be much help.
 
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Old 04-07-14, 06:21 PM
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A/C uses straight 240 and are wired with xx-2 with ground cables, not xx-3. You do not need a neutral.
 
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Old 04-07-14, 09:06 PM
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The links went to blank pages.

A/C uses straight 240 and are wired with xx-2 with ground cables, not xx-3. You do not need a neutral.
That's for the outside units. The air handlers in your attic will probably use 120V hot-to-neutral power.

The "xx"s in PCBoss's post can be replaced with wire gauge numbers once you tell us how many amps each unit draws.

what kind of wire should I run to the air handlers in the attic? Are they standard 120V or are they 240V? Should I run 12-3 or 12-2 for both air handlers?
You may be able to run one xx-3/G cable to take two hots and one neutral to your attic and supply each unit with its own circuit. The size of the conductors needed in that cable depends on the amp draws.
 
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Old 04-07-14, 09:22 PM
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To be on the safe side I'd run a 14-2 w/gr to each air handler. This way if it's 120v or 240v.... you are covered. In your link.... all those air handlers are under 15A so 14-2 is ok.


Your link to the compressors is the complete line. You need the exact model number or the tonnage of each unit.
Most A/C compressors require 10-2 w/gr.
Larger units require a larger wire like 8-2 w/gr.
 
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Old 04-08-14, 05:08 AM
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I appreciate everyone's feedback. I asked my contractor for the part numbers so he should be getting back to me shortly.

As for the tonnage, I am going to have x1 3ton and 1x 2ton. I will use the 10-3 wire that is currently there and probably just run a 12-2 wire for the 2 ton depending on how many Amps it is.

I've been doing my own electric for quite some time now and I am pretty good with it. I looked online and it does not look hard to install the AC disconnects for the compressors. Do disconnects need to be installed for the air handlers as well?

I am contemplating if I should terminate myself...
 
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Old 04-08-14, 12:26 PM
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Do disconnects need to be installed for the air handlers as well?
Yes, although more often than not a switch is used rather than a pull-out disconnect. If it is a 120 volt air handler then a simple single pole switch is acceptable.
 
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Old 04-09-14, 09:14 AM
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I advice determining the ampacity of the circuit conductors in accordance with the values that appear on the equiptments name-plates. I recommend a 12/3 cable for the power-supply to the two A.H. units.

Hint; the NEC requires a receptacle outlet adjacent to any equiptments that are "serviceable", so consider installing such an outlet; best if its a GFI -type receptacle.

What you can do prior to any "Line-Voltage" work is the 24v control wiring; you will need two two-conductor "thermostat" cables between the AHU's and the compressors ; possibly you can route them inside the structure to the closest point where they leave the interior of the structure.
 
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