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Old 04-19-2010, 03:09 PM   #1
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30A Air Conditioner Disconnect


I am having a central air conditioner installed and told the HVAC contractor that I would install the disconnect outside. I have done quite a bit of electrical work at my house, but nothing over the run-of-the-mill 15-20A circuits for receptacles, switches and fixtures.

This is my plan:
- 2-pole 30A breaker in box
- 10/2 wire (white coded hot) from box fished through floor joists to wall penetration
- 1" conduit through wall, to LB, 1" conduit to bottom of disconnect box
- 30A non-fused disconnect box
- HVAC contractor to install "whip" from disconnect to 2 Ton compressor/condenser.

Does this all sound right?

I have a question about the disconnect box. All I find at Lowe's/Home Depot is a fusible disconnect, but the HVAC contractor specifically said, non-fused. Why is this? Should I try a local supplier for a non-fused disconnect?

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Old 04-19-2010, 03:23 PM   #2
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30A Air Conditioner Disconnect


Are you using conduit that is weather proof between the building penetration and the bottom of the disconnect?

If you're using EMT, I don't know if that would be considered "water proof" and therefore not suitable for what I assume is a "wet" location (outdoors in the rain). The disconnect for my AC uses some sort of gray colored flexable conduit between the house and the disconnect. Since there is NM 10/2 running through the basement, and no junction box at the wall penetration, I assum the NM wire continues through this weather protection conduit to the disconnect box.

My disconnect box is then something of a pair of knife like blades (one knife for each of the two hots). The blades are positioned such that you disconnect the power by pulling the "thing" the blades are mounted to. The blades are positioned such that you spin the "thing" around and insert it back into the disconnect. That way, the hots in the disconnect are covered, but the unit is disconnected.

As a guess, the HVAC doesn't want a fussed disconnect because that way you don't have to worry about blowing the fuses (requiring that you either stock the fuses, or run to the local supplier when one of them activates). It's much simpler to only have to worry about tripping a breaker rather than worring about blowing a fuse.

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Old 04-19-2010, 03:34 PM   #3
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30A Air Conditioner Disconnect


I was going to use the grey plastic conduit (Sch 40 I believe) from the disconnect to the LB and through the wall. It should be water tight, because I’m going to glue it. It’s the same material that runs from my meter to the LB and through the wall for the main service wires, just smaller diameter.

The fusible disconnects that I’ve seen are the “knife blade” type as well, but there needs to be a 1/2" +/- fuse in there to make the connection.

I was thinking that the non-fused disconnect would be beneficial for the exact reasons you mentioned. I just don’t understand why Lowe’s/HD doesn’t carry these right in the same spot. Is there a code issue?
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Old 04-19-2010, 03:46 PM   #4
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30A Air Conditioner Disconnect


You should be able to get a non-fused disconnect at your local electrical supply wholesale house. They should also sell retail to you.

If you are running cable outside of the house to the disconnect, you must use the type rated for a wet area. You can set a j-box in the basement and transition to UF or just run UF all the way back to the panel.
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Old 04-19-2010, 03:46 PM   #5
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30A Air Conditioner Disconnect


Not a code issue unless the data plate on the A/C calls for fused protection.
They should be located in the same place, but they may be labeled as a 60 amp disconnect.
You can not run romex inside the conduit.
Mount the disconnect so the cable enters the back of the disconnect.
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Old 04-19-2010, 03:52 PM   #6
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30A Air Conditioner Disconnect


Quote:
Originally Posted by Jupe Blue View Post
If you are running cable outside of the house to the disconnect, you must use the type rated for a wet area. You can set a j-box in the basement and transition to UF or just run UF all the way back to the panel.
Even if it's in an enclosed conduit? Can't I use NM-B in a conduit?
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Old 04-19-2010, 03:55 PM   #7
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30A Air Conditioner Disconnect


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Originally Posted by JPWMU View Post
Even if it's in an enclosed conduit? Can't I use NM-B in a conduit?
Not in a wet location, and outside the house is a wet location.

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