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-   -   Installing Conditioning disconnect (http://www.diychatroom.com/f18/installing-conditioning-disconnect-150496/)

rrodgers 07-16-2012 06:39 PM

Installing Conditioning disconnect
 
I am installing an Air Conditioner 60 amp disconnect on the side of the house and running it up and into the attic in conduit and then over approximately 50 feet and down to a 50 amp feeder breaker with no conduit. What is the correct way to wire this.


I would like to make one unbroken wire run.

stickboy1375 07-16-2012 06:45 PM

Quote:

Originally Posted by rrodgers (Post 967330)
I am installing an Air Conditioner 60 amp disconnect on the side of the house and running it up and into the attic in conduit and then over approximately 50 feet and down to a 50 amp feeder breaker with no conduit. What is the correct way to wire this.


I would like to make one unbroken wire run.

You would have to use UF type wire, but seriously. what ton AC unit do you have, 50 amp feeder is ridiculously high... Do you have the unit on site? What does the nameplate actually require? MAX Breaker, and MIN Amperage is what you are looking for.

rrodgers 07-16-2012 06:54 PM

Information
 
I am going to have a 4 ton unit installed and it seems pretty high to me too. I am going by what the installers requirements are. I do not have the equipment on site, it will be installed in a few weeks. It will be an American Standard and from the specs i found, minimum amps are 28 and protection required 50 amp.

stickboy1375 07-16-2012 06:57 PM

Quote:

Originally Posted by rrodgers (Post 967337)
I am going to have a 4 ton unit installed and it seems pretty high to me too. I am going by what the installers requirements are. I do not have the equipment on site, it will be installed in a few weeks.

I figure 7-8 amps per ton, but that's usually on the high end.... can you wait till the unit is in place before wiring? Im guessing no on this... :)


Some installers don't know how to size a AC unit, Im guessing you could easily run #10 wire and be safe.... but you should ask for the model number or the actual nameplate to save yourself some money in wire...

And don't be scared to install a larger size breaker than wire size you ran... just follow the name plate. :)

mpoulton 07-16-2012 07:00 PM

Quote:

Originally Posted by rrodgers (Post 967337)
minimum amps are 28 and protection required 50 amp.

I assume the 50A rating is the MAXIMUM overcurrent protection, not a minimum requirement. Since the rated current is 28A, you can use #10 wire and any breaker from 30-50A. 30A may trip on startup. 40A would probably do fine. 50A is overkill, but allowed. Your wire size only needs to match the rated current (28A) not the breaker rating.

stickboy1375 07-16-2012 07:07 PM

The reason you can use a much larger breaker on AC systems is because the over current protection is actually built into the hermetically sealed motor, so in essence, the breaker you install is only providing ground fault and short circuit protection, this way the motor will start with its high current start up.

rrodgers 07-16-2012 07:19 PM

Uf
 
So UF 8/3 with a 10AWG ground is the best choice for this job?

Yoyizit 07-16-2012 07:22 PM

Quote:

Originally Posted by stickboy1375 (Post 967339)
I figure 7-8 amps per ton, but that's usually on the high end

Yeah, at a COP of 3.4 and @240v this would be 4.3 A/ton.

stickboy1375 07-16-2012 07:26 PM

Quote:

Originally Posted by rrodgers (Post 967368)
So UF 8/3 with a 10AWG ground is the best choice for this job?

You certainly won't have an issue running #8 UF, that's for sure.

stickboy1375 07-16-2012 07:28 PM

Quote:

Originally Posted by Yoyizit (Post 967374)
Yeah, at a COP of 3.4 and @240v this would be 4.3 A/ton.

Yes, but you have to figure in 125%, and with my numbers, I'm confident on running a wire and not being undersized with equipment unseen.

rrodgers 07-16-2012 07:31 PM

Thanks a million, I have a call in now to the tech to get the nameplate data.

stickboy1375 07-16-2012 07:35 PM

Quote:

Originally Posted by rrodgers (Post 967381)
Thanks a million, I have a call in now to the tech to get the nameplate data.

Lets us know the actual nameplate, you want the MINIMUM circuit ampacity, and the MAXIMUM breaker size.... these numbers are the important ones.

kbsparky 07-16-2012 09:07 PM

Quote:

Originally Posted by rrodgers (Post 967368)
So UF 8/3 with a 10AWG ground is the best choice for this job?

Nope. You are planning to install an oversized cable, with a neutral conductor that will not be needed. #8/3 uf cable is a large, flat assembly and will be unwieldy when trying to install it. It's also very expensive and a waste of money and resources.

All you need is a #10/2 cable for this equipment. The minimum circuit ampacity rating already allows for the 125% requirements of the NEC.

stickboy1375 07-16-2012 09:19 PM

Quote:

Originally Posted by kbsparky (Post 967490)
Nope. You are planning to install an oversized cable, with a neutral conductor that will not be needed. #8/3 uf cable is a large, flat assembly and will be unwieldy when trying to install it. It's also very expensive and a waste of money and resources.

All you need is a #10/2 cable for this equipment. The minimum circuit ampacity rating already allows for the 125% requirements of the NEC.

We don't know the actual nameplate, Im not so sure I would say #10 is sufficient, but probably is... and I completely missed the 8-3, not 8-2 part. :(

kbsparky 07-16-2012 09:44 PM

Quote:

Originally Posted by stickboy1375 (Post 967500)
We don't know the actual nameplate...


From the OP:

Quote:

Originally Posted by rrodgers (Post 967337)
... from the specs i found, minimum amps are 28 and protection required 50 amp.

Taking this at face value, #10 is quite sufficient for the load ...


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