Questions on wiring for light switch in the house for detached garage light

Quijote · Nov 3, 2013

I have a detached garage ~90' from my house. It has power fed to it via an electrician-installed 100A sub-panel running through a PVC conduit properly buried underground.

At the time I also asked the contractor to run a separate 1.5" PVC conduit for a potential future wiring for my generator. That smaller conduit is capped and empty. It runs separate but alongside the main power feed to the garage.

I would like to install a floodlight above the garage door but would like to put a 3-pole switch so I can turn that light on/off from inside the house.

Question: Can I just run a 14/3 UF wire through the empty conduit and be done? If so, can I later also run a 10/4 or 8/4 wire for the power generator through the same conduit?

Thanks!

cnttxmdc · Nov 3, 2013

Quijote said:
I have a detached garage ~90' from my house. It has power fed to it via an electrician-installed 100A sub-panel running through a PVC conduit properly buried underground.

At the time I also asked the contractor to run a separate 1.5" PVC conduit for a potential future wiring for my generator. That smaller conduit is capped and empty. It runs separate but alongside the main power feed to the garage.

I would like to install a floodlight above the garage door but would like to put a 3-pole switch so I can turn that light on/off from inside the house.

Question: Can I just run a 14/3 UF wire through the empty conduit and be done? If so, can I later also run a 10/4 or 8/4 wire for the power generator through the same conduit?

Thanks!

I'd run something heavier than 14 because of the distance (and preference), but it also depends on how much that floodlight will draw. I wouldn't consider anything less than 12, but that's me.

You shouldn't have any problems running an additional wire through there, but make it easy on yourself by taping a heavy string to the wire you run for the light, when you pull it through the conduit. When you go to run the generator wire later, you can use that rope to just pull it right on through.

theoldwizard1 · Nov 3, 2013

If all you are going to run is an outdoor light of less 1000 watts, 14/3 is probably fine. Especially if it is incandescent. Incandescent light can tolerate lower voltage and you should only get about 4-5% voltage drop at that load and distance.

Of course 12/3 would have less voltage drop !

2ManyProjects · Nov 3, 2013

Quijote said:
I have a detached garage ~90' from my house. It has power fed to it via an electrician-installed 100A sub-panel running through a PVC conduit properly buried underground.

At the time I also asked the contractor to run a separate 1.5" PVC conduit for a potential future wiring for my generator. That smaller conduit is capped and empty. It runs separate but alongside the main power feed to the garage.

I would like to install a floodlight above the garage door but would like to put a 3-pole switch so I can turn that light on/off from inside the house.

That should not be a problem, in and of itself. But to remain "code compliant", you must feed power into this circuit from the garage end ONLY. IOW, only the switch loop is run through the conduit back to the house, a la:

Or:

Question: Can I just run a 14/3 UF wire through the empty conduit and be done?

I agree with "cnttxmdc": Over that length run, 12/3 would be better; perhaps not "required" if the only load is one relatively small light fixture, but still...

If so, can I later also run a 10/4 or 8/4 wire for the power generator through the same conduit?

This part, I'm not sure about. Is there some reason you can't run the new wire through the first conduit? Did you not leave a pull rope in there?

Quijote · Nov 3, 2013

Thanks to everyone for the feedback!

Good call on the gauge - I will run 12/3 due to the length. The generator (7kW continuous) has a 30A breaker and 10/4 should be enough, but I plan on using 8/4 just to be safe.

I will be feeding power from the garage sub-panel. I am only extending the switch loop back to the house.

I thought I had thought of everything at the time, but I forgot to tell them to leave a pull rope. After all, I had a second conduit! Ideally, if I can manage to do it, I'd like to run the new, small, switch wire through the larger conduit (2"+) that has the main power feed.

Questions on wiring for light switch in the house for detached garage light

Quijote

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cnttxmdc

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theoldwizard1

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2ManyProjects

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Quijote

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