THHN in Conduit questions

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Old 10-14-09, 11:19 AM
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THHN in Conduit questions

I will be running 12g THHN in 3/4 EMT conduit between junction boxes. Most probably 3 separate runs of EMT each with a single circuit inside.

I am comfortable running romex but THHN I have never done before. I am assuming I need a black, white and a green.

Questions-
Green vs. bare ground within the conduit? I think the answer is Green sheathed vs. bare but I am not sure. Each Junction box is metal and will be grounded also. Ground will be 12g, possibly 10g depending on price just on the theory of possibly upgrading service down the road.
Securing THHN? Between JB's and within conduit there is no way to secure it. I know (at least I think I do ) running romex out of EMT it needs a clamp at the end of the EMT if it doesn't transition directly into a box. Is this the same for THNN? I.e. just pull the cables and make the connections in each JB, no "securing" required at either end?
 
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Old 10-14-09, 11:32 AM
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Originally Posted by ragifiro View Post
I will be running 12g THHN in 3/4 EMT conduit between junction boxes. Most probably 3 separate runs of EMT each with a single circuit inside.
You can fit those three runs into one 3/4" conduit if it makes sense routing wise). You'll need only one ground wire. If you do run one circuit per conduit, you can easily use 1/2" EMT unless you're planning for future upgrades.

Green vs. bare ground within the conduit? I think the answer is Green sheathed vs. bare but I am not sure. Each Junction box is metal and will be grounded also. Ground will be 12g, possibly 10g depending on price just on the theory of possibly upgrading service down the road.
Insulated green or bare is acceptable. If you use the set-screw fittings for your EMT, you don't even need a separate grounding wire since the EMT acts as your continuous ground back to the panel. If you do use a ground wire, it needs to be bonded (attached) at each junction box.
In my opinion, there's no need to upgrade to a 10ga ground, because if you ever do upgrade in the future, you're going to have to pull all new wires anyway.

Securing THHN? Between JB's and within conduit there is no way to secure it.
No need to secure it. Just leave yourself an extra loop here and there in case you do need some slack at some point.
 
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Old 10-14-09, 11:46 AM
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Originally Posted by Zorfdt View Post
You can fit those three runs into one 3/4" conduit if it makes sense routing wise). You'll need only one ground wire. If you do run one circuit per conduit, you can easily use 1/2" EMT unless you're planning for future upgrades.
They do run together for about 10 feet and then go separate ways. Also the two that go the farthest distance semi close to each other are both on the same side of the panel. I don't want to run new romex to adjust one to the opposite side but that may only apply if they share the same neutral, not sure?

3/4 vs. 1/2 is mainly so that I can add later if needed.


Originally Posted by Zorfdt View Post
Insulated green or bare is acceptable. If you use the set-screw fittings for your EMT, you don't even need a separate grounding wire since the EMT acts as your continuous ground back to the panel. If you do use a ground wire, it needs to be bonded (attached) at each junction box.
In my opinion, there's no need to upgrade to a 10ga ground, because if you ever do upgrade in the future, you're going to have to pull all new wires anyway.
My theory was that if I did run a second hot and neutral the ground (now shared) would be over sized and not have to be replaced if what I ran required 10 vs. 12.


Originally Posted by Zorfdt View Post
No need to secure it. Just leave yourself an extra loop here and there in case you do need some slack at some point.
Thanks for the advice on the loop. I was worrying I was missing some secret spy trick clamp with the securing vs. just laying it through there.
 
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Old 10-14-09, 11:58 AM
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Originally Posted by ragifiro View Post
Most probably 3 separate runs of EMT each with a single circuit inside.
If they're going to the same (or linear) locations you can easily pull all three circuits in one 1/2" conduit.

Green vs. bare ground within the conduit?
Either is acceptable for general-purpose. The green is only required if these circuits are powering pool or spa equipment. All circuits in the same conduit can share a single ground wire sized to match the largest hot wire in the pipe.

Securing THHN?
None required, just leave the required 8" looped at each box. No slack is required at pull points (LBs, boxes) which do not contain splices.
 
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