electrical - switched outlet to shop

[Charlie Velasquez]

Getting ready to run electrical to shop

House panel -> 2-2-2-4 mhf -> 2" conduit -> to feed sub-panel in shop (blue in drawing)
House panel -> interlock breaker -> 2-2-2-4 mhf -> same 2" conduit -> generator inlet (yellow)

That much I am fairly certain.
What I also want is a switched outlet so I can turn on a heater or some lights from the house.
My thoughts are a 20 amp circuit, but am toying with running 10g just in case.

This is what I am thinking:
NM-B (romex) in house panel
Breaker ->romex white (properly marked) -> switch ->romex black back to the panel -> romex black +black thwn ->through the conduit to the sub panel enclosure -> Romex to the duplex receptacle with thwn black+romex black, white to sub neutral, green to sub ground.

Saves on wire, saves on distance, saves on conduit fill, saves a space on the sub panel, saves 1500watts on the sub.
So, I would be using electrons from the house panel and the ground and neutral from the shop sub.
Any issues with this?

[John Isgren]

I don’t claim to be an expert, but having been studying NEC as I build out my barn. In my opinion this would not be allowed. You would have a live wire going through your sub panel that would not be shut off if you threw the sub panel breaker.

If you are putting WiFi in the shop you could always use a smart switch.

[Tom M King]

Plus, if you use an arc fault breaker, it won't work. The main reason I wouldn't do it is that it will aggravate the hell out of someone in the future, if they don't get shocked, just by trying to solve an old electrical puzzle.

[Charlie Velasquez]

I don’t claim to be an expert, but having been studying NEC as I build out my barn. In my opinion this would not be allowed. You would have a live wire going through your sub panel that would not be shut off if you threw the sub panel breaker.

If you are putting WiFi in the shop you could always use a smart switch.

John, thanks for the reply. I had not thought of either of those.
A smart switch is more versatile.

I see I could have an insulated hot wire in the enclosure when the rest of the box is dead if the switch inside is closed.
That may be a problem. The sub breaker will be in the house panel, the shop sub will be lugs only. So on the other hand, it may be beneficial to have an outlet I can turn on if I ever have to work on the subpanel. Something to consider.

[Charlie Velasquez]

Plus, if you use an arc fault breaker, it won't work. The main reason I wouldn't do it is that it will aggravate the hell out of someone in the future, if they don't get shocked, just by trying to solve an old electrical puzzle.

No, but a gfci outlet should still work ??

[Art Mann]

John is absolutely right. What you are proposing to do would be very dangerous to someone who is unfamiliar with what you did. No electrical inspector I know would ever approve such a configuration. Also, you haven't increased the capacity of the sub panel at all because the neutral wire would have to be up-sized to carry the additional current from the auxiliary wire. I don't see an exterior disconnect switch at the house. That is a requirement for most places. The requirement is there so that a fire fighter or other first responder can disconnect all power to the out building without gaining entry into the house.

[Jim Becker]

Consider using a contactor with low voltage control to, um...control..the circuit in the shop remotely. You can use low voltage for that or a wide variety of other methods. You are then essentially not going to be schlepping any current...just control...between the two structures/environments. It may be a good ideal to have a positive pilot light at the control location so you know when something is turned on. Now, if you put in something like a minisplit to heat/cool your shop, most, if not all of the decent ones can be equipped with remote control. My Daikon has a WiFi model and I control it from my iPhone.

[Dan Hall]

I spent my entire working life in the electrical construction industry. I taught apprenticeship school for eight years and possess a Life Credential for grades 7 through 14 in vocational education with the subject matter electricity. Your drawing does not use any familiar symbols or standards that I understand. I think what you are planning to do is send a hot and return back through the conduit that supplies power wiring to your shop sub panel so that you can switch a receptacle in the shop from a switch in the house. Correct?

(1) Do not use Romex in conduit. The code forbids it because the wire insulation is not rated for use in conduit (PVC or Metal) Should a problem occur the premises will be inspected post fire and any claim could be denied.
(2) Do not plan or engineer an installation to save $3.00 worth of wire. It's a poor economy. Do all work in compliance with the National Electrical Code and any local ordinances.

From your house panel to the sub-panel is called a feeder. The feeder shall be sized for the load and protected according to it's size by a suitable breaker. For a 220 volt sub panel the wires shall include two hots, a full size neutral and a full size ground. Don't reduce the size of the ground, that is for individual motor and equipment circuits only. All conductors shall be full size. So in your case (220) two hots, a WHITE neutral, and a green or bare ground sized the same.


Now, it is perfectly acceptable to run two wires for a hot and return (neither one of them being white or green in color) in the same conduit as the feeder for the switch you are contemplating but pick that hot up from the sub panel. NOT THE HOUSE PANEL. All three wires going to your heater or service plug will originate in the sub-panel. The ground and neutral don't have to go all the way back to the house panel. Just the two wires for hot and return. If you insist on having that plug serviced from the house panel (to run a service light when working on the panel) then run a separate conduit in the same ditch with a hot, neutral and ground from the house panel to the special use receptacle. Don't mix the conductors anywhere along the way. I can see a situation where direct burial cable might be preferred but again, only when the hot, neutral, and ground ALL originate in the same panel. OK?

While on the subject here, what is a neutral anyway? It's a current carrying conductor for doing work. What is a ground? It is a conductor for carrying FAULT current back to the supply point for the purpose of interrupting power via a circuit breaker. It carries fault current only. Otherwise it just sets there. (Or sits there. depends where you're from) The worst violation I see by DIY types all the time is to use a green or bare wire in place of a neutral. Because it seems to work. Don't do it. It sets up what are called circulating current paths. They can kill. The code says that the neutral and the ground will be connected together at any convenient place between the service entrance conductors and the first disconnecting means and NO OTHER PLACE. When we make what is called a separately derived system by installing a transformer between the service (say 277/480) and the low voltage supply for a building (117/208) the neutral on the downstream side of that separately derived system shall establish a NEW ground/neutral link at the transformer and no other place.

So what does that mean? Say your shop is in a separate building (as we all so desperately desire). The ground wire from the service feeder in the house is connected to the ground buss in the sub panel. But never the neutral. OK? Only the supply feeder neutral connects to the neutral buss in the sub panel. Throw away that long green screw that comes with the sub panel from Home Depot. You need to buy a neutral kit for the sub panel that isolates your neutral buss from the sub panel box
.
BTW. With a separate service in an outbuilding you must drive a ground rod out there and connected it with a #4 stranded or #6 solid copper conductor to the ground buss in the sub panel. The solid #6 is way easier because it can be run without conduit protection from a suitable ground clamp (following structure) to the sub panel. The reason a #6 is ok regardless of the service size is that tests have shown the current carried by a #6 is the maximum that can be dissipated by the ground rod.
BTW. I hope I don't have a hundred of these BTW moments. If you feed a service receptacle from the house I would put a Brother label on there saying something like: "Fed From House Panel"

[Tom M King]

Dan, that's one of the best posts I've ever seen on any forums. Do you really live in a place named Sparks?

[Dan Hall]

Dan, that's one of the best posts I've ever seen on any forums. Do you really live in a place named Sparks?

Well thanks Tom. I enjoyed writing it and very much appreciate your comment. I do live in Sparks. The folks over on a welding forum I used to frequent got a kick out of it too.

[Charlie Velasquez]

The unanimous opinion is to keep circuits in the shop, in the shop; and circuits in the house, in the house.
So, I will investigate smart switches per John’s suggestion or low voltage per Jim’s.

Thank you for the feedback.

[Mike Cutler]

Dan
i do like your post!
Ground and neutral are probably the most misunderstood concepts encountered on forums by folks, that don't work with electrical systems.
I work in a nuclear power plant and we have "Earth ground", "Station Ground", "Equipment Grounds", "System Commons" and diode suppressed common returns for noise immunity.
Knowing what "Your Ground" potential is really at is critical.
Once again, nice post.

[Charlie Velasquez]

Along that line, any recommendations for an outlet/switch?
The distance from house to shop would be about 60 ft., another 5-10 ft to the outlet.
The outlet would be a dedicated 20A, 120v circuit to feed a 1500w heater and a 13w led exterior light (if the light is on, the heater is on... my original plan was to have the interior switch be a timer so I wouldn’t forget to turn off the heater)

The shop wall: 2x4 construction - vinyl siding, 3/4” eps insulation, 1/2” fiberboard sheathing, 2” eps between the studs, 1/2 ply interior sheathing for wall covering.
I will also run a 1” conduit for low voltage, internet, whatever.

[John Lanciani]

(1) Do not use Romex in conduit. The code forbids it because the wire insulation is not rated for use in conduit (PVC or Metal) Should a problem occur the premises will be inspected post fire and any claim could be denied.

And once again the urban legend is repeated. Article 334.15(B) of the 2017 National Electrical Code reads as follows;

"Protection from Physical Damage. [NM and NMS] Cable shall be protected from physical damage where necessary by ridgid metal conduit, intermediate metal conduit, electrical metallic tubing, schedule 80 pvc conduit, or other approved means."

You certainly can, and in some circumstances must, put NM cable (romex) in conduit. What you can not do is use the individual conductors from NM cable, and only because they are not properly labeled.

[Dan Hall]

Right you are John. Protected from physical damage where necessary. Like exposed in a shop below 7'6" above the floor. And indeed those wires may well be the equivalent of THHN or TW insulation but because they are not labeled as such then they aren't approved for use in conduit systems. The general statement that I made is certainly true in the work proposed by the OP where romex is to be used along with other conductors in a PVC raceway. But thank you for bringing up the exception to further the conversation. Urban myth, I'm not so sure.

Section 334.15 is entitled "Exposed Work". One cannot then project that section into a general statement regarding the use of romex in a conduit, cable tray or other approved raceway systems. According to this section one can also specify sheetrock, plywood or a lumber nailing strip. The section is not about the raceway, it's about the protection from damage.