0

I have 1" conduit running out to a gazebo on my patio. I would like to install a 240 circuit for 2 infrared heaters and a 120 circuit for a ceiling fan. Based on the heaters I want to use (2 3000W heaters that each draw 12.5A), I need to run 8-gauge wire for them. Can I fit 2 8-gauge conductors, an 8-gauge ground, and 2 12-gauge conductors for the ceiling fan? I was intending to use the 8-gauge ground to also ground the ceiling fan.

EDIT: Conduit is SCH 40 Cantex

5
  • Which type of conduit? The inside diameter varies a little; it's possible that a set of wires meet the fill rules for one type of 1" conduit but exceed the allowance for another.
    – Greg Hill
    Jul 11, 2021 at 14:47
  • It's true there's a small difference in ID's @greghill, but they'd have to be using crazy-big wire before that would matter on 1". Jul 11, 2021 at 17:32
  • Do the installation instructions specify circuit size requirements? Instructions are part of UL/CSA/ETL Listing and by NEC take priority above general circuit requirements. Jul 11, 2021 at 20:42
  • @NoSparksPlease I have not received them yet but from the online documentation I have looked at Jul 11, 2021 at 21:05
  • Why not just put a small sub panel in the gazebo and feed it with #6 Al? Jul 11, 2021 at 21:10

2 Answers 2

2

4 circuits

Note that a Multi-Wire Branch Circuit counts as 1 circuit.

You are really very unlikely to overfill a 1" conduit, unless you get into some crazy-huge wire, maybe lol.

Get into some crazy-huge wire, maybe!

You'll go broke putting #8 copper in that pipe. So if you even needed wire that large, use #6 aluminum instead. It's perfectly fine for large feeder like this. It attaches directly to the circuit breaker on the breaker end. On the other end, use 2-port "MAC Block connectors" (which are halfway between an Alumiconn and a Polaris in size and cost. One port takes the #6Al wire, and the other port takes 2x #12 for going onward to your heaters.

Actually let's review the amperages for each size of wire that is THWN or XHHW wire inside conduit which is permitted 75C thermal.

  • #14 Cu = 20A 15A due to 240.4(D) limitations
  • #12 Cu = 25A 20A due to 240.4(D) limitations
  • #10 Cu = 35A 30A due to 240.4(D)
  • #8 Cu = 50A
  • #8 Al = 40A
  • #6 Al = 50A

But you probably don't need wire that large.

Not least, because the allowance for 4 circuits is a game-changer.

Look closely at the heater's rating. Here's what you thought: "it's a 240V heater and computing 3000/240V = 12.5. When we apply a 125% derate, we get 15.625, x2 = 31.125A." Look again.

You may find it is a 250V heater. Now compute 3000/250V = 12.000. When we apply a 125% derate, we get 15.000A. X2 = 30A. Wow, it's almost like they sized the heater for that.

And even if it's a long run, we don't really care about voltage drop on a heater. The heater doesn't care. It's certainly not going to be bothered by 10% voltage drop. So getting spendy on thick wire isn't constructive.

8
  • Thanks for the detail. The heater specs say 240V an 12.5A. Everything I have found says that due to derating, in order to support 2 of those heaters I would need 8GA wire and a 40A breaker. I am sure I could make it work with 10GA and a 30A breaker but trying to do it the right way. Jul 11, 2021 at 17:20
  • If this was attached to (or part of) your house, the easy solution would be 2 x 20A 12 AWG circuits. I suspect (Harper can confirm) that you can't do that because circuits to other structures are "one circuit of each type". Jul 11, 2021 at 17:24
  • @manassehkatz that's a good point. Jul 11, 2021 at 17:31
  • What is meant by the comment "one circuit of each type"? Jul 11, 2021 at 18:19
  • 1
    Type means a 120V circuit, vs. a MWBC, vs. a 240V circuit, vs. a 120/240V circuit. You can only have one of each voltage, unless there's something special about it like being switched from the house. Jul 11, 2021 at 18:21
0

To answer your question, yes 3@#8 and 2@#12 will fill in sch 40 pvc only 16%, which is less than half of the allowed 40%.

But your ground will be larger than required, #10 copper is good for 60A for ground.

But why not run two separate 20A circuits for the heaters and use all #12? 4 wires for two heater circuits, two wires for fan, and a ground. Would all fit in 1/2" pvc, no fancy wire connectors, 125% rating for fixed electric satisfied, derating for 6 current carrying is satisfied, voltage drop is good for 200', easier to work on if fault develops.

5
  • Why not just put a small subpanel in the gazebo? Jul 11, 2021 at 21:08
  • @Craig a subpanel might seem a bit out of place on a gazebo, though technically just fine. Jul 11, 2021 at 21:36
  • I don't know, I think a small outdoor-rated breaker box would probably fit nicely behind a rose bush or under a bench? ;-) homedepot.com/p/… Jul 13, 2021 at 0:39
  • @Craig (a) Panel needs to have workspace in front of it - so under a bench for sure won't and have to be careful about bushes/etc. too; (b) once you go to subpanel, you also need cutoff switch (which could probably be done with this little panel by using 2 spaces for a feed breaker) and (c) once you go to subpanel also need ground rods. All makes sense for a shed/workshop/garage, but perhaps a bit overkill for a gazebo - even though the subpanel itself costs very little. Jul 13, 2021 at 3:29
  • If it’s a bench that you can just scoot away from the wall, I don’t see what the problem is. If it’s built-in, it would be different. Aug 8, 2021 at 20:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.