Feeder & switch wires in same conduit to detached building?

[malibu101]

I know this has been asked before and after searching I must ask this simple question. I am helping a buddy plan and we are stumped on this.
It is not getting inspected but we want to insure that it is NEC code compliant if he were to sell the place and have it inspected.

100A subpanel feed from the house to a pole building. All in conduit and all properly sized.
He would like (2) 3-way switches at the garage door and the house door to operate exterior lights on both the garage and the house from each location.
Simple enough.

QUESTIONS-
1- Can the (8) #12 THHN run through the same conduit as the feeders to the garage? Conduit sized properly of course.
2- If so; Should they be fed from one structure or the other?

 

[Norcal]

Are the conductors tapped from the meter, or are they off the house panel? If yes to the first part, then absolutely not, but either way I would run another conduit.

 

[theoldwizard1]

Are the conductors tapped from the meter, or are they off the house panel? If yes to the first part, then absolutely not, but either way I would run another conduit.

I would NEVER tap directly off of a meter !

Second conduit is not required. Good question on where the "source" should be from.

You might consider some of the modern "wireless" 3 way switches. The remote one mounts on a wall in the house. It looks like a normal switch with a switch plate ! Battery powered.

 

[Bert_]

I would probably run another conduit. Another 3/4 - 1" PVC is cheap. Nothing wrong with running them in the same pipe though. Only thing to watch is that you might have to derate your wires if you have to many in one conduit.

Source should be the sub panel. That way there is only a single feed to the garage and either panel can de-energize the circuit since it would pass though both panels.

 

[alfredeneuman]

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QUESTIONS-
1- Can the (8) #12 THHN run through the same conduit as the feeders to the garage?

Why 8? (the equipment ground in the feeder will cover the grounding duties.)

 

[malibu101]

I would probably run another conduit. Another 3/4 - 1" PVC is cheap. Nothing wrong with running them in the same pipe though. Only thing to watch is that you might have to derate your wires if you have to many in one conduit.

Source should be the sub panel. That way there is only a single feed to the garage and either panel can de-energize the circuit since it would pass though both panels.

Never thought of derating for the conductor count. Good catch!

Thanks all for the answer that it can be done.

 

[teamextreme]

I can't imagine you would have to count all 3-way switch travelers on a conductor count, seeing as only one per group would be energized at a time. Also not sure why you need 8 wires. Worst case I see is if you are planning on 2 pairs of 3 ways, each controlling an independent light on each end, then you'd need 6. If it's one pair of 3 ways controlling a commonly connected light on each end, then you'd only need 4.

And you need to source power from the pole barn to be legal.

 

[malibu101]

I can't imagine you would have to count all 3-way switch travelers on a conductor count, seeing as only one per group would be energized at a time. Also not sure why you need 8 wires. Worst case I see is if you are planning on 2 pairs of 3 ways, each controlling an independent light on each end, then you'd need 6. If it's one pair of 3 ways controlling a commonly connected light on each end, then you'd only need 4.

And you need to source power from the pole barn to be legal.

Both lights can be on at the same time if wished.
We just figured to pull the ground wires for the (2) switch circuits along with the travellers. Just like using (2) 12/3 NM cables.
So yes, we could get away with only 6 wires between the buildings IF we use the ground of each building on each end.

Thanks!

 

[Dirtydan69]

I would NEVER tap directly off of a meter !

Second conduit is not required. Good question on where the "source" should be from.

You might consider some of the modern "wireless" 3 way switches. The remote one mounts on a wall in the house. It looks like a normal switch with a switch plate ! Battery powered.

I have one of those in my house. Slight delay but works as it should.

 

[wyliesdiesels]

I would NEVER tap directly off of a meter!

Second conduit is not required. Good question on where the "source" should be from.

You might consider some of the modern "wireless" 3 way switches. The remote one mounts on a wall in the house. It looks like a normal switch with a switch plate ! Battery powered.

I wouldnt either but its done quite often...

And yeah he could run UF-b...

I can't imagine you would have to count all 3-way switch travelers on a conductor count, seeing as only one per group would be energized at a time. Also not sure why you need 8 wires. Worst case I see is if you are planning on 2 pairs of 3 ways, each controlling an independent light on each end, then you'd need 6. If it's one pair of 3 ways controlling a commonly connected light on each end, then you'd only need 4.

And you need to source power from the pole barn to be legal.

Actually, it would be 2 per group because one traveller and the wire on the common screw would be energized all the time on the source switches and energized when the light is on, on the load switches.

Code however, says to count the current carrying conductors so would be 6. I would have to look and see if theres any exceptions for 3 way lighting circuits.

 

[Bretny]

Cant he use motion lights? Even if its one on the house and one on the garage.