Conduit inside the home

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broddo
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Conduit inside the home

Post by broddo » Sun Feb 10, 2019 9:38 am

I'm finding it hard to find any information on running power cables through conduit inside of the home. My internet searches are providing mixed results - some say it's allowed, some say it's not. I'm finishing off my basement at the moment but I will probably need a few cable runs in the future for a new split air con system. However, I don't want to leave the basement walls bare for the next few years and I'd rather not have to destroy the drywall again whenever I get around to running the cabling

I thought that running some conduit with a guide wire might be a decent solution. That way, at a later date, I'll be able to pull through whatever cabling is required.

What do you think? Will this meet code? If so, what kind/size of conduit should I get?

Thanks!

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Aaron
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Re: Conduit inside the home

Post by Aaron » Sun Feb 10, 2019 11:26 am

Good planning on your part for thinking of your future needs.

It's important to distinguish between cables and wires. Cable is two or more wires bundled in a sheath. Cords are cables that have plugs at the end of them, for electrical appliances. Wires are individually insulated copper conductors.

If you're talking about running power cable or cords through conduit, then no, that is not permissible. Electrical installations need to be fixed and permanent, and the only power that can be used within conduit are Type THHN/THWN wire for 120V or 240V power.

Conduit is most commonly EMT, or electrical metallic tubing, and it terminates from one electrical box to another. Ten foot lengths can joined together with couplings. Because the EMT always terminates to an electrical box or panel, the contents of the conduit are always individual conductors or wires.

You can certainly run empty conduit to an empty electrical box in anticipation you will use it eventually, though. If you anticipate you're going to pull a 120V circuit, then 1/2" conduit is fine. If it's 240V, it may be safer to run 3/4" conduit.

broddo
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Re: Conduit inside the home

Post by broddo » Mon Feb 11, 2019 8:11 am

Great information there Aaron, thank you. I was indeed thinking of running NM cables through the conduit but from what you've said, it looks like this can't be done. But THHN/THWN should be no problem for this application.

If EMT always terminates to an electrical box/panel does that mean it can only supply one circuit?

Are there other types of conduit that are allowable behind drywall? I see Home Depot sells ENT (flexible blue conduit), "schedule 40" PVC and a non-metallic liquitight coil.

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emtnut
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Re: Conduit inside the home

Post by emtnut » Mon Feb 11, 2019 6:41 pm

broddo wrote:
Mon Feb 11, 2019 8:11 am
If EMT always terminates to an electrical box/panel does that mean it can only supply one circuit?
No, it can terminate to an electrical box and extend to 2 or 3 circuits from there. Just be aware to have a large enough box for the conductors.
Also, if you have more than 6 wires (not including the ground wire) you need to derate the ampacity (ie, upsize the wire)

broddo wrote:
Mon Feb 11, 2019 8:11 am
Are there other types of conduit that are allowable behind drywall? I see Home Depot sells ENT (flexible blue conduit), "schedule 40" PVC and a non-metallic liquitight coil.
ENT is fine also, it can be a pain to fish the wires in thou. PVC is acceptable too, personally I prefer EMT.
The liquidtight is usually just used to protect a small section of NMD (romex)
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Aaron
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Re: Conduit inside the home

Post by Aaron » Mon Feb 11, 2019 11:37 pm

EMT is my favorite, the only thing that makes me not use it for everything, besides cost, are the bends—specifically offset and saddle bends to clear obstacles. Pro electricians spend years mastering the skill of conduit bend calculations and execution.

But if you’re doing a straightaway run, then it's great and easy.

No, no NM through conduit. You'll need a junction box terminating both the NM cable and the EMT in order to splice the NM cable's wires to the THHN wires going through the EMT. Unless, of course, you run the EMT straight to your panel, then the THHN wires can terminate at the breaker and neutral/ground bus bars.

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emtnut
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Re: Conduit inside the home

Post by emtnut » Tue Feb 12, 2019 8:11 am

For most PVC and EMT installs, you can usually get away with pre-made 90s 45s and box offsets.

But yeah, for anything beyond basic you would need a bender.
In a pinch, you can bend PVC with a 'heat n strip' blower :mrgreen:
Those air heaters come in handy for unthawing frozen snowblower augers as well ... ask me how I know !! :roll:
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broddo
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Re: Conduit inside the home

Post by broddo » Tue Feb 12, 2019 9:49 am

Great advice guys. I have a few tricky bends so PVC might be the better choice (even better that it can be heated to help it bend!) I'll leave a few guide strings in there to help me pull the wires through. I have no problem running conduit the full way - breaker to box - using THHN.

Planning for the future is like this is always a good idea, but can be frustrating trying to think of everything. I finished running the pex supply lines for the infloor heating and just remember that the new zone will also need a thermostat. It would have been a pain if I had forgotten that!

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Aaron
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Re: Conduit inside the home

Post by Aaron » Tue Feb 12, 2019 3:06 pm

emtnut wrote:
Tue Feb 12, 2019 8:11 am
For most PVC and EMT installs, you can usually get away with pre-made 90s 45s and box offsets.
I totally forgot those exist! I do have a bender. I've actually been successful in some offets. I particularly like doing box offsets, they just look really cool--a little jog to line up with the holes in the J-boxes.
emtnut wrote:
Tue Feb 12, 2019 8:11 am
In a pinch, you can bend PVC with a 'heat n strip' blower :mrgreen:
Those air heaters come in handy for unthawing frozen snowblower augers as well ... ask me how I know !! :roll:
Yeah I actually heard of putting tape at the end of the PVC pipe and filling them with sand before heating and bending. The sand supposedly preserves the inner diameter.
broddo wrote:
Tue Feb 12, 2019 9:49 am
Great advice guys. I have a few tricky bends so PVC might be the better choice (even better that it can be heated to help it bend!) I'll leave a few guide strings in there to help me pull the wires through. I have no problem running conduit the full way - breaker to box - using THHN.

Planning for the future is like this is always a good idea, but can be frustrating trying to think of everything. I finished running the pex supply lines for the infloor heating and just remember that the new zone will also need a thermostat. It would have been a pain if I had forgotten that!
You WILL forget something. It's almost guaranteed. There's always regrets and hindsight-20/20 when doing improvements or renos to the house. Fact of life.

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