# 240 volt circuit and 120 volt circuit to shed



## fortop (Jun 23, 2010)

My neighbor wants to wire one 240 volt circuit and one 110 volt circuit to his small shed, about 30 feet from his house. I suggested 1" PVC conduit 18" underground, with 3 each #8 THWN wires (red, white, black - very old style ungrounded 240 volt equipment, so no provision for ground) for the 40 amp rated 240 line, and 3 each #12 THWN (red, white, green) for the 110 volt 20 amp rated outlet. Three questions:
1) Does this sound like the correct conduit size, wire size, and conduit depth?
2) Does the shed need a separate disconnect panel inside the shed, or are the cords from the appliances inside the shed sufficient "disconnect" ?
3) Does this installation require "derating" (i.e. larger wire size required) due to underground location? This is in southern Arizona? 
Thanks.


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## Scuba_Dave (Jan 16, 2009)

You can't run 2 seperate circuits to a detached structure
As far as I can tell with the power needed he would need to run a sub panel
Best bet is probably a 60a sub

Derating (voltage drop) depends upon the distance


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## fortop (Jun 23, 2010)

I thought this might have to do with sharing a neutral, which is why I recommended separate neutrals for separate circuits.


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## AllanJ (Nov 24, 2007)

To have both 120 and 240 volts at the shed or other separate building you must run one combination 120/240 volt circuit aka multiwire branch circuit. (It has two hots, one shared neutral, and one ground).

To have more than 20 amps of 240 volts or more than two 20 amp subcircuits of 120 volts you must have a subpanel out in the shed.

Thirty feet to the shed would not need de-rating; use #6 gauge wires (copper) for 60 amps.


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## fortop (Jun 23, 2010)

So, any thoughts on how to wire this? 60 amp 240 volt panel in shed? What size wire/conduit, etc.? Can the 60 amps be supplied by a 60 amp breaker in the house circuit panel?
I am not clear on the multiwire branch circuit, if both circuits have separate conductors supplied by separate circuit breakers (separate branches) in the main house panel. For example, what if two separate runs of conduit provided power to the two separate circuits?


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## Jim Port (Sep 21, 2007)

You need to run a feeder out to a subpanel nounted in the shed, not two circuits. The circuits will be split in the subpanel.

Check this sticky for a better idea of the process.

http://www.diychatroom.com/f18/stubbies-diagrams-other-stuff-52338/


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## fortop (Jun 23, 2010)

So, one circuit (240V or 120V) can be supplied to the shed with the only disconnect being the circuit breaker in the main service panel, and no sub panel or ground rod needed in the shed - correct?


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## Scuba_Dave (Jan 16, 2009)

One circuit 

OR a MWBC


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## joed (Mar 13, 2005)

Under 2008 code you need the fourth wire for ground.


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## fortop (Jun 23, 2010)

I would use the green wire for ground, to ground the 110 volt (GFCI) circuit. The old 240 volt equipment has no provision for equipment ground. 
So, if the shed were physically attached to the house - just run conduit for all conductors to the outlets in the shed - correct?


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## Scuba_Dave (Jan 16, 2009)

Suddenly the shed 30' away is connected to the house? :huh:


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## fortop (Jun 23, 2010)

Not saying the shed will be connected to the house, just asking the question - looking for the answer, exploring options: virtual "duplicate service entrance" sub panel in the yard shed, with double ground rods, etc., vs. running cable in conduit on the wall of the existing building. I have never had a high powered shed myself - couple of high powered cars though


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## frenchelectrican (Apr 12, 2006)

Fortop.,

To make it simple ., Nope you must have one circuit which it will be MWBC going to the shed and you can have big as 60 amp with 16mm²{ #6 AWG } THHN/THWN conductors in the conduit and by the way it must run full 4 conductors { Black , Red , White and Green } and with subpanel keep the netural and ground seperated on subpanel and install the main breaker in there that is your main disconnection for your subpanel.

For conduit depth it will need at least 18 inches { most area will ask for 24 inches anyway }

and for 120 volt recepetals it must have RCD { GFCI } protection and I am pretty sure that will included the luminaries as well { the 2008 NEC code stated all 120 volt circuits}

240 volts no it not need RCD unless you are dealing with pool pump { that will be diffrent ball park of game to deal with it }

But really I will recomend that you do the load demand to make sure it will handle the addtional load without issue.

No., you do not need to derated the conductor size due you are very short distance from the load centre.

Merci.
Marc


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## Speedy Petey (Feb 1, 2004)

fortop said:


> So, one circuit (240V or 120V) can be supplied to the shed with the only disconnect being the circuit breaker in the main service panel, and no sub panel or ground rod needed in the shed - correct?





fortop said:


> I would use the green wire for ground, to ground the 110 volt (GFCI) circuit. The old 240 volt equipment has no provision for equipment ground.
> So, if the shed were physically attached to the house - just run conduit for all conductors to the outlets in the shed - correct?


Absolutely not. You cannot combine the 40A 240v circuit with the 20A 120v circuit. 

You MUST install a sub-panel in the shed _to do what you want_. 
You need a 50 or 60 amp feeder (60 will be better).
You need a sub-panel with a main disconnect.
You need a ground rod (or two) at the shed.

The 240v circuit does not have, require or need a neutral. Just two hots and a ground. If the equipment does not have a ground, I'd find a way to get one on it.


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## fortop (Jun 23, 2010)

Thanks everyone for the responses.
I was not suggesting combining a 240 volt and 120 volt on one circuit - I was asking about either one 240 volt OR one 120 volt circuit as an option to avoid the separate sub panel with disconnect in the shed. I was asking what would one 240 volt circuit or one 120 volt circuit require at the shed.
So, I see 3 options:
1) 1" PVC underground conduit 18" minimum deep, with #6 wire (4 insulated conductors - red, black, white, green) supplied from a 60 amp breaker in the main house service, with 2 ground rods driven in at the shed, with 60 amp sub panel in shed, containing one 60 amp main breaker, one 40 amp breaker for the 240 volt equipment, and one 20 amp breaker for the 120 volt GFCI outlet. The manufacturer of the 240 volt equipment specifies red, black, white (neutral) with no ground - but rig up another ground to the equipment frame anyway.
2) Eliminate one circuit at the shed. Have only one 240 volt or one 120 volt circuit at the shed. Supply the one circuit from a breaker in the main house service (240 volt 40 amp, or 120 volt 20 amp) with separate insulated conductors in 1" PVC conduit 18" deep (4 conductors for 240 volt,or 3 conductors for 120 volt. No sub panel or separate disconnect or ground rods needed at the shed.
3) Forget the detached shed. Attach the shed to the side of the house. Run 1" PVC conduit with 4 #8 conductors for the 240 volt circuit and 3 #12 conductors for the 120 volt circuit. Attach conductors to appropriate 240 volt outlet and 120 volt outlet in the shed. 
Do I have this right? Thanks.


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## AllanJ (Nov 24, 2007)

Your three alternatives are good.

Also:

A 120 volt only feed for more than 20 amps also requires a subpanel if you want to feed receptacles and lights.

I thought that a standard feed of red, black, white, and green, regardless of amperage, was the same thing as a combined 120 and 240 volt circuit.

A 240 volt only feed (actually also a 120 volt feed or 120/240 volt feed) of more than 20 amps can terminate in your shed with a single receptacle intended for the voltage and amperage. In the case of a 30+ amp 120 volt circuit, such a receptacle will not accept ordinary plug in appliances and lights.


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## xxPaulCPxx (Dec 2, 2006)

I'm curious why you don't want to do a subpanel here? It's the only thing that gives you maximum flexibility and safety, and doesn't really cost much money.

Workwise it's just a little more labor, but there is such a big payoff.


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## fortop (Jun 23, 2010)

My neighbor plans to use this shed for 3-5 years, then sell the property - either taking the shed with him, or selling the shed and contents outright at time of sale.The somewhat temporary nature of this setup points toward least cost and effort. Future "resaleability" of these items and reasonable value is questionable if not impossible Driving 2 ground rods 8' long through Arizona caliche (rock like hard clay) is not something I am eager to do. I see the additional cost:
2 ground rods and clamps
60 amp or higher subpanel
2 additional 60 amp main breakers (in shed and main house service panel)
#6 vs. #8 wire for the shed service
Rental cost for power (maybe pneumatic with air compressor) impact driver for ground rods (and hope you don't hit any utility lines on the way down).
Just looking for the easiest route possible - now leaning toward shed attached to house - though I think that has the least attractive appearance and most hassle to remove without leaving a trace, upon future sale of house.


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## xxPaulCPxx (Dec 2, 2006)

Gotcha - those are good reasons.

Here is another possible option: Set up an RV style power supply. Then, you can wire in the shed with a panel BUT have it supplied with a flexible cable plug to the outlet instead of a direct conduit link.

An RV parking spot with power might make for plus for a future purchaser.


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## Hazmatt4602 (Jun 24, 2010)

fortop said:


> My neighbor wants to wire one 240 volt circuit and one 110 volt circuit to his small shed, about 30 feet from his house. I suggested 1" PVC conduit 18" underground, with 3 each #8 THWN wires (red, white, black - very old style ungrounded 240 volt equipment, so no provision for ground) for the 40 amp rated 240 line, and 3 each #12 THWN (red, white, green) for the 110 volt 20 amp rated outlet. Three questions:
> 1) Does this sound like the correct conduit size, wire size, and conduit depth?
> 2) Does the shed need a separate disconnect panel inside the shed, or are the cords from the appliances inside the shed sufficient "disconnect" ?
> 3) Does this installation require "derating" (i.e. larger wire size required) due to underground location? This is in southern Arizona?
> Thanks.


 How many amps is your 240 volt line? You should be able to run 2 #12 and 3 #10. But it depends on your amp draw. Or run 3 wires plus a ground and put a sub panel out to the shed, and cut down on your wire runs.


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## xxPaulCPxx (Dec 2, 2006)

Hazmatt4602 said:


> How many amps is your 240 volt line? You should be able to run 2 #12 and 3 #10. But it depends on your amp draw. Or run 3 wires plus a ground and put a sub panel out to the shed, and cut down on your wire runs.


You really do have to read the other posts first... like the one three replies back from here:thumbup:


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## fortop (Jun 23, 2010)

The 240 volt line is 40 amps - manufacturer states minimum #8 wire, 3 wire hookup with no ground provision on this equipment, 50' maximum wire run to equipment allowed. 120 volt line is just for one 20 amp rated circuit, so 3 conductors 12 GA + insulated ground for that.


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## fortop (Jun 23, 2010)

The RV power idea sounds intriguing. The largest I have seen is 50 amp, but the style of 240 plug is different, and I am not sure my neighbor will go for a high voltage cable lying on the ground supplying power to his shed. The 240 receptacle is 6-50 style on the equipment.


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## xxPaulCPxx (Dec 2, 2006)

Actually, I was thinking that he run the conduit out to next to the shed and up to an outlet on a post. The post would be next to the shed. The shed would have the cable coning out of a box with a weatherproof stress relief fitting and connect to the outlet without sitting on the ground - no long extension cords!

The cord would feed the lugs on the panel.

Like I was saying, think about that shed being an RV, then place the pole where it would make sense for an RV to plug into.


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## fortop (Jun 23, 2010)

So, what would be the requirements for the RV pedestal? Does it need to have ground rods, GFCI, etc. When you say the cords would feed the lugs on the panel, do you mean that the cord would go from the RV pedestal to a sub panel in the shed - then to a 240 volt and 120 volt circuit? Seems like you would have to cut the end of a RV power cord and wire it into the sub panel. 
I wonder if a GFCI spa box could be mounted on the shed, with 4 conductors to the spa box, 240 volt and 120 volt circuits built in, with main disconnect. Of course, a spa is not a "detached building" per NEC, but the theory seems the same to me. We could put a bird bath inside the shed and say the shed was just a shade cover for the spa.


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## xxPaulCPxx (Dec 2, 2006)

Yes, you would use the 50 amp plug wire to power a small breaker panel. the Hot lugs would be connected to the red and black, the neutral bus to the white wire, and the unbonded ground bus to the green wire. Then you place your 40 amp breaker and 20 amp breaker in the panel as usual.

I'm not sure about grounding requirements for RV outlet... though we are kind of cheating this a little, you might want to put the ground rods in anyway. I have pretty hard soil too, and I was able to pound them in with a regular metal post pounder (capped metal tube with handles).


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## fortop (Jun 23, 2010)

Since we are thinking "outside the box", any thoughts on a Spa Box - could be 60 amp 240 volt with two built in 120 volt circuits - all protected by GFCI main breaker? From what I read, this just requires 4 conductors from the main service panel, as long as all conductors are insulated. Might be the cheapest/cleanest solution, and might have some resale value in a few years when the owner moves (although I know used equipment is not allowed per NEC rules.)


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## fortop (Jun 23, 2010)

Just curious, if there was a 240 volt, 60 amp spa box on the shed (all GFCI), would the ground fault on the spa box trip if it was connected to a 3 wire (no grounding conductor) 240 volt equipment plug. (The plug has no grounding conductor - from the factory that way.)


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