Rewire A/C System

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  #1  
Old 06-01-08, 01:03 PM
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Rewire A/C System

I am fairly good with working on electrical work around my home. I am not a licensed electrician, but have enough sense what to do and not do when it comes to electrical safety.

With that said, I will soon have my main central AC system replaced - I chose a Carrier 21 seer Infinity system. My current system is on the west side of my house jammed in between pool equipment and another condensing unit (I have two systems) and faces the sunlight most of the day. The air handler/furnace is in my attic about 65 ft from the condenser.

I want to relocate the condensing unit to the east side of the house to provide more breathing room for the condensing unit and will put it closer to the air handler in the attic (now only be about 25 ft away). But, I will need to have electricity run from the circuit panel to the new location.

Here are my questions related to wiring (I plan to re-wire this myself):
1) What gauge wire should I run for this distance?
2) The wire will be run in the attic for approx 70 ft. to the breaker box - any concerns I should be aware of running this wire?
3) What type/size of disconnect box should I use oustide?
4) What size circuit should I install in the breaker box? I don't have any of the electrical specs for the Carrier unit.
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  #2  
Old 06-01-08, 01:20 PM
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Before anyone can give you a correct answer you need all the data from the unit nameplate.

Most times a 30 amp unfused disconnect is fine, but if the unit says MAX FUSE you would need a fused disconnect.
 
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Old 06-01-08, 01:23 PM
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Without the electrical specifications no one can advise you on what is needed.

You can probably use a 60 ampere disconnect at the location of the condensing unit and you will need a 120 volt receptacle near the condensing unit. I would make the receptacle a 20 ampere circuit and, of course, GFCI.
 
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Old 06-01-08, 08:09 PM
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Found specs on the Carrier 21 system - 24ana1.

Says the Max Fuse or Circuit breaker amps = 20

This equates to #14 wire per the NEC table 310-16, which seems rather small for an ac system.

Please advise.
 
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Old 06-01-08, 08:21 PM
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Not really., due the art 440 they have specal cause on the amparage rating on the A/C motor But however you mention 70 feet IMO you should stick with #12 AWG size minumin sizewise.

I useally sized by following items.

Full load amp
Max fuse or circuit breaker rating

that about it with wire size but however ya have to becarefull some manufacter if stated fused disconnected not mention breaker then you have to use the fused disconnected switch there otherwise a standard A/C pullout will useally meet the code as long it marked Fused or Circuit breaker.

Merci,Marc
 
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Old 06-01-08, 08:25 PM
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You didn't read the footnote that states #14 is limited to 15 amperes, #12 is limited to 20 amperes and #10 is limited to 30 amperes.

Run #12 wire or cable. If you use conduit you may use individual conductors and also run the #12 conductors for the 120 volt, 20 ampere convenience receptacle that needs to be within (I think) 20 feet of the unit.

You will need a 20 ampere, 2 pole circuit breaker for the condenser unit and the convenience receptacle needs to be either a GFCI type or fed from a GFCI circuit.
 
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Old 06-01-08, 08:34 PM
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Furd .,, Yes i did read the footnote about it and i did mention in the forum he should run #12 wire anyway

But Furd if you read the NEC code related to the A/C section it will change a bit there it will be in both art 430 and art 440.

Merci,Marc
 
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Old 06-02-08, 12:01 AM
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Not you, Marc, I wouldn't dream of correcting you. I meant that gbreezer80 had not read the footnote.

I am also familiar with articles 430 and 440 although I admit I didn't check them before responding.

Your post came through as I was writing mine.
 
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Old 06-02-08, 08:50 AM
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Guys - thanks tons for the info.

Do I really need a convenience recepticle for the condensing unit outside? I currently have another run to the attic furnace/coil with a switch and recepticle.

Any preference on what kind of wire I run using 12 gauge to the condensing unit?
 
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Old 06-02-08, 10:40 AM
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Actually, I was given incorrect info for the sizing of the circuit....20 amps was for a 2 ton unit....I will be putting in a 5 ton system which requires (per the electrical specs) a 50 amp circuit.

What gauge wire do I need to run for a 50 amp circuit?
 
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Old 06-02-08, 10:50 AM
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If you are going run the wire in the same route then you will have to use the # 6 copper with a 60 amp pullout disconnection switch.

Now let get to the other issue senice you mention about the outdoor repectale near the outdoor unit by per NEC code if you have a outdoor repectale withen 25 feet from the unit that fine otherwise you will have to add one near to it.

{ if you can get the manufacter specs that will be great then we can able dail in little better with the wire size }

Merci,Marc
 
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Old 06-02-08, 11:17 AM
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I have seen disconnect boxes with these convenience recepticles in them. Would I need to run #14 wire for this too for 110 service?
 
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Old 06-03-08, 08:31 AM
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After measurements, I need to run approx 100ft of wire from disconnect to breaker panel.

The specs for the AC unit is 50 amps....so could I run #8 for a 50 amp service at this distance and be okay?

The city inspectors use the 2005 NEC as their reference
 
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Old 06-03-08, 06:16 PM
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Go with #6 due you mention length there.

Are you going to run this conductor thru the attic area or all the way on outdoor wall ?

It may change the choice of materal you can use on this one.

Let us know what your intend run is.

Merci,Marc
 
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Old 06-29-08, 03:27 PM
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Thanks for the replies....sorry it's been a while since my last post, but here are the specs for wiring my AC system.

50 amp max load (will be using a 50amp double pole breaker)
60 amp non-fused disconnect box
6/2# NMB wire (with bare copper ground) - run is about 90 ft. total

Question:
Is this the correct gauge wire I chose for this? The wire will be run in the attic (approx 70 ft) and run in conduit (rubber liquid tight) on each side of the house (10 ft each) - one to the disconnect box and the other to the breaker panel.

I could not run the wire down the inside wall to the breaker panel from the attic, so I had to run it outside under the soffet in the conduit - drilled a hole in the brick wall just on the other side of where the breaker panel is located and routed the wire through the hole (put a junction box just outside the hole).

By the way...I live in Texas where my attic temp gets around 120 degrees during two months in the summer.
 
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