New Shed Subpanel

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Old 04-11-16, 12:17 AM
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New Shed Subpanel

First off, im new to the forums. Please let me know if I'm doing anything wrong (ie Posting in the wrong place, etc.)

I'm planning on putting a Subpanel in a new Shed on my property, roughly 20 feet away from my house. I'm going to run conduit underground, as the thought of running direct burial wire with no extra protection gives me shivers.

My question is regarding which type of wire I should run through the conduit. A friend of mine recomended that I use UF wire, even though it's rated for direct burial. Another person recommended THHN. I'm not really sure what I need to run, as I've never run anything underground before.

After careful deliberarion, I don't think I'll ever need this feed to be able to support more than 20 amps total, and that's really pushing it.

Im also wondering, if i were to run something rated for direct burial, does that change the depth at which the conduit must be burried?

Any suggestions would be appreciated. Thanks.
 
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Old 04-11-16, 01:19 AM
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UF is cable not wire. Wire is a single conductor. Best practice is to not run cable in conduit. Iis more difficult to pull and work with. If you use cable you do sleeve it with conduit where it enters and leaves the ground.

For amperages of 60 amps or less THWN wire is usually used. THHN is for dry locations and can not be used in wet locations. Buried conduit is considered a wet location. Given the advice from your friends it almost sounds like they work at the BigBox store.
After careful deliberarion, I don't think I'll ever need this feed to be able to support more than 20 amps total, and that's really pushing it.
Then you don't need a subpanel. You just need either 12-2 UF direct buried at 24 inches or three #12 THWN wires (one black, one white, one, green) in PVC conduit buried 18".

There is a burial depth exception for a single 120 volt 15a or 20a feed. If protected by a GFCI it can be buried at 12".
 
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Old 04-11-16, 08:29 AM
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If all you need is 120V 20A circuit to the shed then the cheapest and easiest is to just bury the 12/2 UF 12 inches and feed it from a 20A GFCI breaker or GFCI outlet back at the source/house. You can put it in conduit if you like to but is not necessary. Also a sub panel is not required, just use a junction box to split out the wiring to the outlet(s) and light(s). Keep all wire as #12 in the shed.
 
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Old 04-11-16, 11:54 AM
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I should have specified. I want a sub panel in the shed because of what I will be running. I keep reptiles and have a heater running 24/7 that I want on its own circuit. That way, if the heater were to over draw for any reason, it would blow it's own breaker and the rest of the heating elements would stay on. The heater has a max draw of 1500 watts. The other elements are extremely low draw.
 
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Old 04-11-16, 12:09 PM
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30 amps 120/240 is the usual minimum for a subpanel and you would need four #10 wires (black, red, white, green) or 10-3 UF.

A 60 amp main lug panel would be enough. You would need a ground bar in addition to the supplied neutral bar. (Usually you have to buy the ground bar separate.) The neutral bar is not bonded to the panel so if present any bond screw or strap needs to be removed.

You will need to drive at least one "x8' ground rod. It is connected with #6 to the ground bar.

Note if you were to use 20 amps for the feed it would be just as likely for the 20 amp breaker at the house to trip killing all power as it would be for the 20 amp in the subpanel to trip. Going to 30 amps would make that less likely.
 
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Old 04-13-16, 10:41 PM
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Okay, now out of curiosity, is there anything wrong with simply installing multiple breakers in my main house panel and running thwn through conduit, into the shed? Specifically, multiple circuits through the same conduit. Do I need a seperate grounding rod for the shed in this scenario?
 
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Old 04-14-16, 04:41 AM
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The code says only one feeder to a structure so you cannot have multiple breakers and different circuits. A multi wire branch circuit is one circuit and can be run.

A rod is required for more than one circuit.
 
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Old 04-14-16, 06:31 AM
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Thanks so much for the info, guys. I'll repost if I have more questions.
 
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Old 04-15-16, 06:32 AM
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A 20 amp multiwire branch circuit (typically black, white, red, ground conductors) delivers the maximum power (equivalent of two 20 amp circuits) without the need for a subpanel.

More than 20 amps on any hot conductor, including one 30 amp 120 volt circuit (black, white, ground) and you must have a subpanel because ordinary lights and receptacles must be protected by breakers not exceeding 20 amps. MWBCs must be wired into the feeding panel breakers with 240 (or 208) volts between the two hot conductors.
 
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