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bbddt 04-27-2011 05:05 PM

electric for shed
Need Help
I have been reading alot on this subject so my question is this.... I buried underground conduit 5 years ago when i built shed but not really knowing what i was doing i used 1/2 conduit so now how can i run electric there from my main panel. everyone says use a sub panel but i dont think i can through 1/2 conduit because of size of wire needed. Is there any way to do this? I think i really messed up by using 1/2 but i had no idea any suggestions. Thank You

Jim Port 04-27-2011 05:30 PM

You can still add a subpanel in the outbuilding. The size of the conduit will severely restrict the circuit size that can be taken out there tho.

sirsparksalot 04-27-2011 06:23 PM

1). Dig it up, and install 2"
2). Run arial service

what is the 5-year-old conduit serving now?

secutanudu 04-27-2011 07:33 PM

Doesn't sound like it's serving anything....

If you just want lights and basic (120v) outlets in the shed, you should be fine and not need a subanel.....what is it you want to use in the shed?

Is it PVC conduit? SCH 40? SCH 80?

How long is the run? Not having to account for voltage drop (long run) will help.

Assuming the run isn't too long (less than 125 fee or so), you could get away with either:

1 x 30A 120/240v subpanel (4 #10 THWN wires in a multi-wire branch circuit)


2 x 20A 120v circuits (4 #12 wires...2 hots, neutral, ground)

Of course, this all depends on how easy it will be to pull wire through your conduit (number of bends, etc).

I'd opt for the subpanel.

For reference:

Raceway fill calculator:

Voltage drop calculator:

bbddt 04-27-2011 08:01 PM

run is only 50ft I have a pool which i never thought i would have so electric would be for pool filter, gas heater for pool, 1 light in shed, maybe 2 outlets in shed (no power tools), n maybe couple outlets on deck for pool. only bends in conduit is 90 where it comes out of ground near house and shed otherwise its straight. can i run a 40 amp out there and do sub panel and do that?

bbddt 04-27-2011 08:03 PM

not sure what sch 40 or 80 is and even if i did i wouldnt know what kind of conduit i used sorry. just know its grey and is used for underground

bbddt 04-27-2011 08:05 PM

not servicing anything I just ran it in case i needed it. so i thought ahead there but never thought of running anything bigger than 1/2.

Jim Port 04-27-2011 08:15 PM

The grey makes it sound like PVC conduit.

Schedule 40 and 80 refer to the thickness of the conduit wall. Sch 80 is thicker than Sch 40.

You do not have enough space in a 1/2" conduit to run #8s for a subpanel. You only have room for 4 #12's.

bbddt 04-27-2011 08:31 PM

yes it PVC conduit not sure of sch 40/80 so if i run 4 #12s thats just one circuit at the main panel? and that will cover what i need?

secutanudu 04-28-2011 12:02 AM

you will have 2 x 20-amp circuits if you run 4 #12 THWN (red, black, white, green). You would install a double-pole 20A breaker, red and black go to the breaker, white & ground go to the bus bars. The neutral will be shared among your two circuits.

THis is called a multiwire branch circuit (MWBC), and can only be safely done via a double-pole breaker that spans across both hot buses in your panel.

vsheetz 04-28-2011 03:12 AM

How deep is the conduit buried?

bobelectric 04-28-2011 05:30 AM

Run another 2" conduit and use the " conduit for phone line. 60 amp min.

AllanJ 04-28-2011 09:08 AM

If you run the 10 gauge wires for 2x30 amps, you will still need the subpanel. Here you can have four 20 amp breakers, two on each side of the line.

If you run new conduit, it is suggested you plan for at least 2x60 amps with 6 gauge wires (aka a 60 amp 120/240 volt circuit).

bbddt 04-28-2011 01:22 PM

im not looking to run new conduit i ran what i have before i had grass and dont want to re dig.. the conduit is bout 24-30 inches deep. alittle confused on the "2" 20amp circuits? if i run 4 #12 to shed wouldnt black and red go to 20 amp circuit in main and white n green go to bus bar now isnt that 1 20 amp circuit? can someone clear this up please. If i want "2" 20 amp wouldnt i have to run 8 #12..4 for each?

secutanudu 04-28-2011 04:03 PM

4 wires on a double-pole breaker would give you (2) 120v circuits. Each circuit has one hot (red for one, black for the other). The circuits would share a neutral (white) and ground (green).

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