Wiring for AC unit

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  #1  
Old 11-27-10, 11:16 AM
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Wiring for AC unit

Hi all,

I've got a neighbor that is going to help me with the electrical installation for a mini-split ac unit. I want to have everything ready to go for when he gets home from his Thanksgiving trip so that when the AC guys get here everything is ready for them.

Please help me understand what I need to purchase to install the AC sub-panel. I need to know what size breaker, wire and anything else that I may need.

The electrical requirements state that for the 12,000 BTU unit the following:

Minimum Circuit Ampacity: 12 A
Maximum Overcurrent Protection (Time Delay Fuse or HACR Circuit Breaker): 15 A

I'm relatively ignorant about electricity, but what I do believe we are going to do is install a new breaker into the main panel, run a line to the other side of the house (part of the run is going to be outside), install an AC electrical cut-off box near where the outdoor unit will be positioned. I've seen the AC cut-off box just like the other units have so I'm assuming I just purchase the same type of unit.

Is there anything else that I need? Thanks for helping me save time when he gets back!
 
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Old 11-27-10, 11:31 AM
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One big question..which will determine everything else. 240VAC or 120VAC? The Pro's may know from the info you provided...but why not beat 'em to the punch.

Oh and welcome to the Forum!
 
  #3  
Old 11-27-10, 11:44 AM
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Thanks for the welcome...this site looks like I could lose hours of work time reading all the great information!

I'm not sure of the answer to your question...here is the only other information that I can find about the unit (I don't have the unit...just looking at the installation guide on the internet):

TYPE HEAT & COOL MODEL
MODEL INDOOR UNIT ASU12RLS
OUTDOOR UNIT AOU12RLS
POWER SUPPLY 208/230 V 60 Hz
COOLING CAPACITY 12000 BTU/h
INPUT POWER 0.83 kW
CURRENT 3.9 A
HEATING CAPACITY 16000 BTU/h
INPUT POWER 1.20 kW
CURRENT 5.5 A

For anyone wondering it is a Fujitsu 12RLS mini-split for our attic.

http://www.e-comfortusa.com/PDF_file...ice_Manual.pdf
http://www.e-comfortusa.com/PDF_file...n%20Manual.pdf
 
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Old 11-27-10, 11:51 AM
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Thats what was needed....when the Pro's check in they'll be well informed.

Yes..looking through all the posts can be addictive. Almost every repair imaginable has been listed at one time or another...but never take someone elses issue as gospel...just ask.
 
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Old 11-27-10, 02:12 PM
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Current draw for your mini split is only 5.5 amps at 240 volts so a 15 amp circuit will be fine. You feed the circuit to the outside unit. Then you will need to run a 3 wire (14/3 or 12/3 if you choose to use a 20 amp circuit) with a ground between the outside and inside unit. This cannot just be NM-b. UF is minimum but this must be protected from damage. You will also need a 2 pole disconnect at the outside unit and by the inside unit. Outside I suggest a standard weather proof A/C disconnect. Inside can be a 2 pole switch.
 
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Old 11-27-10, 03:16 PM
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Give us more info on how you are going to route the wiring. Is the breaker box on the outside of the house? Is it on the same side as where the outside unit will go? Is there an unfinished attic or crawl space wiring can be run in? One story or two story house. If two story is the inside unit going on the first or second floor.
 
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Old 11-27-10, 03:37 PM
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The breaker box is in the garage against an outside wall.

The only access I have to run the electrical is to go out the wall from above the breaker box and then can run it down about 6 feet into the crawlspace. From there I will just come right out where the AC cutoff box will be.

I have hardiplank cement siding and figure I must need some way to 'tap' into the wall outside of the breaker box and then run the 6 feet to the crawl space with some sort of weather protecting covering. In the crawlspace I will just tack it in place every few feet along the run.

I don't think I need a switch for the internal unit on a mini-split. The AC installer didn't mention needing one and I don't recall seeing anything in the installation guides either. All that is called for is a line set run from the outdoor to indoor unit. Even if it's not called for, should I install a two pole switch as suggested?

Thanks for the help!
 
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Old 11-27-10, 05:08 PM
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The breaker box is in the garage against an outside wall.

The only access I have to run the electrical is to go out the wall from above the breaker box and then can run it down about 6 feet into the crawlspace. From there I will just come right out where the AC cutoff box will be.
Do the house and garage share a wall? If so why not down the wall and into the crawl space?
 
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Old 11-27-10, 06:21 PM
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Nope, no common wall between the house that I can use to easily get to the crawlspace. Line will have to run out the back of the garage, down the wall, and then over 6 feet to the crawlspace.
 
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Old 11-27-10, 07:14 PM
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Originally Posted by chamill View Post
Nope, no common wall between the house that I can use to easily get to the crawlspace. Line will have to run out the back of the garage, down the wall, and then over 6 feet to the crawlspace.
You will need to use UF and sheath it with PVC conduit where it runs down the outside wall. You can end the PVC below ground and continue the cable to the house at a minimum depth of 24".
 
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Old 11-28-10, 12:08 PM
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I don't think I need a switch for the internal unit on a mini-split. The AC installer didn't mention needing one and I don't recall seeing anything in the installation guides either. All that is called for is a line set run from the outdoor to indoor unit. Even if it's not called for, should I install a two pole switch as suggested?
Yes, a service disconnect is required by NEC regardless of whether it is mentioned in instructions or not. However, the disconnect switch could be built into the inside unit. Is there a manual switch on it that turns off all power or are there just lugs to wire into?
 
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Old 11-28-10, 12:15 PM
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Originally Posted by CasualJoe View Post
Yes, a service disconnect is required by NEC regardless of whether it is mentioned in instructions or not. However, the disconnect switch could be built into the inside unit. Is there a manual switch on it that turns off all power or are there just lugs to wire into?
Agreed. Instructions even show a disconnect between the outside and inside unit (Fig. 11). I have wired that brand before and there never had been a disconnect, only lugs (screws)
 
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