How to connect external PVC electrical conduit to interior box?

[PILOON]

Often overlooked is that an expansion sleeve should be used where conduits leave the ground as frost can (and usually will) break or otherwise damage your nice watertight conduits.
They are sold in most sizes common to buried conduits.

 

[CincyFlyer]

Their isn’t code or manufacture specs I have seen that limits NM or Romex in conduit. I’m just assuming he is using NM/Romex based on the description. If it’s individual wires- yes a box or back to back LBs.

I agree. It's widely believed that you cannot, but I've never found it in any code.

 

[s219]

Often overlooked is that an expansion sleeve should be used where conduits leave the ground as frost can (and usually will) break or otherwise damage your nice watertight conduits.
They are sold in most sizes common to buried conduits.

They are also important for long runs, as PVC can expand quite a bit with temperature. I have one on the ~ 12' run of PVC up the wall on my house where my generator wiring enters the home, and another on the ~ 40' run of PVC across the inside wall of my garage. When I heat my workshop (one bay of the garage) in winter, I can actually see and hear the PVC change length along that 40' wall and see the expansion sleeve change. It's pretty wild.

 

[medic0648]

4 #8 THHN/THHW are approximately 21% fill for a 1"schedule 80 pvc pipe. But if you ever plan on or think you will plan on increasing the capacity in the future install larger pipe. Plus it will be easier to pull the wire. Not knowing the intended demand or the distance I can't guide you on wire size. Also sch 80 is required where exposed when using pvc.

 

[plowhog]

I like the idea of a box on the outside wall instead of using an LB, such as in the picture from S219.

If I go that route, it probably will greatly reduce the chance of me needing to use the cable stretcher during or after install. :laughing:

 

[hr3]

I agree. It's widely believed that you cannot, but I've never found it in any code.

It's in the code book if you have a conduit running in the ground it's considered a wet location.. romex is not allowed.

 

[STx]

1" conduit will.be plenty big enough for 4 strands of #8 THHN. That said, I've never wished I'd used smaller conduit at a later date but, have often wished I'd gone a little larger, conduit is cheap and you're already digging the ditch, so....

When I built out the shed on my place, I only ran 100a service to it because it was just meant to be a weekend place. My wife one day surprised me and said we should just move here and we're now putting on an addition that includes central air and electric heat, an oven, etc. Our 100a service isn't going to cut it any longer. I only ran 1.5" conduit when I pulled the original wires so now, instead of just pulling new wire through the existing conduit, I'm going to have to dig a new trench and lay conduit. Garages have a tendency to get power creep as well. A couple of big 240v tools or some other toy may have you needing more than 30a in the future. I'd say install at least 1.5" conduit, the cost difference is negligible and if you do need it in the future, you'll be glad it's there.

And yes, a male adapter and locking nut is the right way to install it to the box.

Since you're running a sub-panel, you'll need 4 wires, 2 hot, 1 neutral and a ground. The ground wire can be smaller than the others. In the panel, your ground should be isolated, not bonded.

 

[CincyFlyer]

It's in the code book if you have a conduit running in the ground it's considered a wet location.. romex is not allowed.

I mean above ground. I ran Romex in a chase, and then in conduit for twenty feet, to feed my air compressor.

 

[plowhog]

I'm thinking about putting in 2" conduit for the high voltage and 1" for the phone / low voltage. Someday I might pull bigger wires thru ...

My licensed electrician is a friend, so it's not like a bid situation with a spec. I have only spoken to him on the phone about this project. I described wanting power to this garage building but never discussed whether it is just a run of wire to plugs, or whether to use a subpanel. I said I just wanted lights and plugs, nothing exotic. He will be here next week to do wiring and I am doing the trenching and conduit in advance of that.

The panel I will be tapping from is in the nearby barn, about 30 feet away. It is a Zinsco, either 50a or 70a. It currently has a twin 30a breaker for the well, and a few additional RED breakers that power barn lights and plugs. I think those are 20a or 15a breakers, not sure. I can check and also get some pictures. There is one open slot in the panel that will accommodate a twin 30a breaker.

I bought two new Zinsco 30a twin breakers. ($$) One is to replace the well breaker since it "sizzles" when you flip it on and off. (!) The other is to run the power to the nearby garage. Two questions:

1. For my setup, is another sub-panel in the newly heated up garage preferable to just adding some plugs?
2. What is an isolated ground? Is that a ground rod at the garage location, connected into the panel?

I tried to google isolated vs bonded ground and became more confused than when I started!

 

[STx]

I'm thinking about putting in 2" conduit for the high voltage and 1" for the phone / low voltage. Someday I might pull bigger wires thru ...

My licensed electrician is a friend, so it's not like a bid situation with a spec. I have only spoken to him on the phone about this project. I described wanting power to this garage building but never discussed whether it is just a run of wire to plugs, or whether to use a subpanel. I said I just wanted lights and plugs, nothing exotic. He will be here next week to do wiring and I am doing the trenching and conduit in advance of that.

The panel I will be tapping from is in the nearby barn, about 30 feet away. It is a Zinsco, either 50a or 70a. It currently has a twin 30a breaker for the well, and a few additional RED breakers that power barn lights and plugs. I think those are 20a or 15a breakers, not sure. I can check and also get some pictures. There is one open slot in the panel that will accommodate a twin 30a breaker.

I bought two new Zinsco 30a twin breakers. ($$) One is to replace the well breaker since it "sizzles" when you flip it on and off. (!) The other is to run the power to the nearby garage. Two questions:

1. For my setup, is another sub-panel in the newly heated up garage preferable to just adding some plugs?
2. What is an isolated ground? Is that a ground rod at the garage location, connected into the panel?

I tried to google isolated vs bonded ground and became more confused than when I started!

I would do a sub-panel, it gives you more flexibility down the road for changes.

When you install a panel, it comes with a bonding screw to bond the neutral and ground. It's essentially bonding the neutral buss to the enclosure. You are only supposed to bond on the first panel, all sub-panel should be fed by 4 wires, 2 hots, 1 neutral and a ground. Sub-panels should not have the bonding screw installed so you have physically separate neutral and ground busses. Yes, you should install a separate grounding rod to ground the building, panel, etc and it should be connected to your ground bar but, your power will actually use the 4th wire you ran for the ground for fault current in most cases. We always say electricity is trying to find a path to ground but, that's not entirely correct, it actually wants to find it's way back to it's source and that's what the isolated ground is for on sub-panels. If you bond them, you run the risk of stray current on the ground wire, which can give a little bite when touching metal appliances. If you skip it and only install a ground rod at the garage, then you're relying on the conductivity of the ground to carry fault current, which isn't a safe situation.

The current code requires 4 wires for sub-panels with just a couple of exceptions, one of which is if you use metal conduit which acts as the ground, I can't remember the other offhand.

Your friend will probably be better able to explain it than I can. I'm not an electrician, I just know enough about code and electricity to do my own residential work without killing myself or burning the house down while keeping the PoCo happy enough to make connections for me. I've put 2 services in from scratch here, one for the cabin and one for the shop.