Garage Power Disconnect

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mkgrady

Senior Member
Location
Massachusetts
I’m planning to run power from a residence to a new detached garage for a door opener, lights and a few outlets for small power tools. I’m going to run one 20 amp multiwire branch circuit and run all 20 amp NM cable inside the garage. The branch circuit feeding the building will be 12-3 UF installed in conduit.

My question is about the disconnect. I will use a two pole 20 amp snap switch. Does the disconnect have a location requirement? There will be an underground conduit run to the building but it will not enter the building near an entrance. Does the disconnect need to be near the entry door? Can it be located inside or outside the building?
 

Leespark57

Senior Member
Location
Boston, MA, USA
See 225.32

Located inside or outside, readily accessible, nearest the point of entry of the conductors (does not need to be near the entry door). Two single pole switches would be fine (up to 6 disconnects). FYI, no grounding electrodes needed with individual branch circuit or MWBC.
 

mkgrady

Senior Member
Location
Massachusetts
See 225.32

Located inside or outside, readily accessible, nearest the point of entry of the conductors (does not need to be near the entry door). Two single pole switches would be fine (up to 6 disconnects). FYI, no grounding electrodes needed with individual branch circuit or MWBC.

Thanks. That makes sense. I was thinking if the circuits ran through part of the building to get near the entry that that would not make sense. I think I will put the disconnect outside so it will be accessible. If I put it inside they will probably just pile junk in front of it. Maybe I’ll put a sign near the entry that says the disconnect is behind the building.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I would opt for #10 on 30a - same labor, room for expansion.

Home Depot sells a 30a 2-pole toggle switch, by the way.

You could install a 6-circuit panel with no other disconnect.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Maybe I’ll put a sign near the entry that says the disconnect is behind the building.
I routinely put them at 48" on center above the floor on the inside (more secure) and label them as "vacation disconnect" to give them a little more context for the homeowner.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
I would opt for #10 on 30a - same labor, room for expansion.

Home Depot sells a 30a 2-pole toggle switch, by the way.

You could install a 6-circuit panel with no other disconnect.

You use a panel and that would invoke the requirement for a GEC at the separate building. IMO.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Okay, I'm pretty sure there's a rule around here somewhere that prohibits making too much sense. Stop that. :p
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I would use a two pole switch and not worry about the end user piling junk in front of it, chances are no one will ever use it anyway. :)
 

mkgrady

Senior Member
Location
Massachusetts
Thanks guys. Using a combination of your ideas I think I will run 10-3 UF from the house in 1-1/2 conduit, put a 6 circuit panel in side and drive a rod.
 

newservice

Senior Member
Thanks guys. Using a combination of your ideas I think I will run 10-3 UF from the house in 1-1/2 conduit, put a 6 circuit panel in side and drive a rod.

Old thread but I think romex in conduit is a violation for that distance.

So, if I get this right, for a multiwire ..two 20a circuits to the detached garage overhead you could use 10/3 UF on the guy wire, bond the guy wire to the ground?.. a double pole 20 non GFI breaker in the service panel, to a DPST disconnect switch in the garage, then receptacles on one leg and lights on the other. No panel and no ground rod.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Old thread but I think romex in conduit is a violation for that distance.

So, if I get this right, for a multiwire ..two 20a circuits to the detached garage overhead you could use 10/3 UF on the guy wire, bond the guy wire to the ground?.. a double pole 20 non GFI breaker in the service panel, to a DPST disconnect switch in the garage, then receptacles on one leg and lights on the other. No panel and no ground rod.
Why do you feel that #10 conductors overhead would be better than #10 conductors underground? What would be the violation that you've mentioned?
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
Old thread but I think romex in conduit is a violation for that distance.

So, if I get this right, for a multiwire ..two 20a circuits to the detached garage overhead you could use 10/3 UF on the guy wire, bond the guy wire to the ground?.. a double pole 20 non GFI breaker in the service panel, to a DPST disconnect switch in the garage, then receptacles on one leg and lights on the other. No panel and no ground rod.
I believe the OP indicated running UF in the conduit not the NM, thus not a violation. If it was romex (NM) it would be violation on a couple of counts.
 

newservice

Senior Member
I believe the OP indicated running UF in the conduit not the NM, thus not a violation. If it was romex (NM) it would be violation on a couple of counts.

I hear you but I disagree, even though I can't say why.
Other than it's using 2 wiring methods combined. For one thing you would have to de-rate the UF right off the bat for being installed in the conduit. There aren't charts that I can find for that. NM isn't prohibited from being run in conduit either ( "uses not permitted"), nor is UF, but we still know you can't do it.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Old thread that took a tangent.

You most certainly can run a cable assembly in conduit. In fact the conduit fill requirements even describe how you should treat cables for calculating cross section.

You might bump into issues such as proper fastening of the cable at the end of a conduit, or you might hit location restrictions, but that is separate from the general concept.

For example the conduit required for 10-3 UF is probably larger than the conduit required for 4 #10 THHN wires, and you couldn't run NM in an underground conduit, but 10-3 UF in a suitable underground conduit is just fine.

Jon
 

retirede

Senior Member
Location
Illinois
I hear you but I disagree, even though I can't say why.
Other than it's using 2 wiring methods combined. For one thing you would have to de-rate the UF right off the bat for being installed in the conduit. There aren't charts that I can find for that. NM isn't prohibited from being run in conduit either ( "uses not permitted"), nor is UF, but we still know you can't do it.

Why would UF need to be derated simply for being in conduit?

Nothing wrong with mixing wiring methods as long as the transition is proper.

NM is prohibited in wet locations. Conduit outdoors is a wet location.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I hear you but I disagree, even though I can't say why.
Other than it's using 2 wiring methods combined. For one thing you would have to de-rate the UF right off the bat for being installed in the conduit. There aren't charts that I can find for that. NM isn't prohibited from being run in conduit either ( "uses not permitted"), nor is UF, but we still know you can't do it.

Your first sentence says it all. How can you disagree if you don't know of any code to support your theory. Then you say UF must be de-rated in conduit- another off the cuff statement that isn't true. Then you agree the nm and uf is permitted in conduit but say you still can't do it.

I am asking you please to not make statements without some type of logic or code to back it up.
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
I hear you but I disagree, even though I can't say why.
Other than it's using 2 wiring methods combined. For one thing you would have to de-rate the UF right off the bat for being installed in the conduit. There aren't charts that I can find for that. NM isn't prohibited from being run in conduit either ( "uses not permitted"), nor is UF, but we still know you can't do it.
All code references NEC 2017
NM is prohibited from being used in wet locations, 334.12(B)(4) any conduit run out of doors is automatically considered a wet location regardless of glued connections.
UF rating requirements found in table 310.15(B)(16)
How is transitioning from UF to NM once inside using a 2 wireing methods violation? Both 60°c wire. Even if using THHN in conduit pull you wouldn't be prohibited from transitioning to NM inside, just would calculate based on the lower rated 60°c cable
 

newservice

Senior Member
Im sorry. I guess Ive been licensed for 25 years and rely on my instinct too much. I was dangling my statements out for your feedback and I see I got it.
My original question was regarding an overhead, not underground, installation to a garage, where you run the UF with a guy wire.
The underground discussion of running UF in a pipe was my afterthought on the OP post and I didn't realize it stirred a hornet nest.
For the record Fred I don't see where I said anything at all about transitioning from UF to NM or for running NM outside or wet locations.
310.15 B 16 says nothing about ampacities for UF cable installed in conduit. Its allowable ampacities for insulated conductors and cables.

Not trying to be confrontational here guys just searching for answers
 
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