Need some more info before I begin subpanel

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Old 04-04-10, 08:19 PM
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Need some more info before I begin subpanel

I am still in the planning stage for an upgrade to add electrical to a shed using a 60amp feed to a main lug load subpanel. I am reading as much NEC material as possible but have found some glaring deficits of information that I need to proceed. Any help would be appreciated.

1) I planned on using 6-3 THHN / THWN wire underground at 18" but I am getting alternative info about UF wire which I assumed was running wire without PVC 40 conduit. Is UF safe in PVC conduit? Could I even run UF from the exterior Main breaker to the subpanel??? Since I haven't bought any wire yet I figured I would ask, as this stuff is expensive. I wouldn't want to bury 6-3 THHN in conduit and find out I needed UF. Seems safer to go with UF but am hearing too many opposing viewpoints and am concerned as I would rather be safe than sorry.

2) Expansion fittings on PVC 40 and where are they appropriate to install? Are they needed? NEC says they are but where on the PVC (ends?)

Thanks again.
 
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Old 04-04-10, 09:09 PM
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If you run UF conduit is only needed where it comes out of the ground. If you run conduit all the way it is best to use THWN. If you use a main lug subpanel you are limited to six breakers. To add more you would have to add a disconnect.
 
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Old 04-05-10, 07:50 AM
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As Ray posted UF only needs to be protected by PVC where exposed. Inside a wall/floor cavity is considered protected.

UF will need to be buried a minimum or 24" if direct buried.

PVC that is buried should not need expansion fitting due to the ground temp staying fairly consistent.
 
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Old 04-05-10, 09:47 AM
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Originally Posted by idoltwilight View Post
add electrical to a shed using a 60amp feed to a main lug load subpanel.
People have a different meaning for what a "shed" is, but 60 amps is a pretty hefty feed. Are you intending to use big tools or welding machines? Most sheds are just fine with a 20A multiwire branch circuit.
 
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Old 04-05-10, 05:40 PM
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Thanks for the info. As far as 60 amps I wanted to eventually have a dedicated heater that would pull a lot of electricity (4000-5000 watts on a 30 amp circuit) as I can only take one more year watching the kids play video games in the winter. I figure I can grow into it rather than redo the thing in a few years.
 
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Old 04-05-10, 09:11 PM
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Thats one hello of a heater! 30amps?? Seems a little excessive for a shed, must get really cold in your area. Anyway that would leave you with 2 15amp breakers to work with power and lighting. How big is this "shed"?
 
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Old 04-05-10, 10:07 PM
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Originally Posted by SilverTattoo View Post
Thats one hello of a heater! 30amps?? Seems a little excessive for a shed, must get really cold in your area. Anyway that would leave you with 2 15amp breakers to work with power and lighting. How big is this "shed"?
maybe its a heater that just requires a 30 amp circuit???.. usually then its closer to a 20 amp working load
 
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Old 04-06-10, 05:48 AM
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300 sq feet "shed". But the 60 amps aren't enough if you ask me as the subpanel will feed a small attached garage too. 30 amps to a heater if that is what a dedicated heater with such power would safely need but I just want to make sure that I have enough power available for future. For now it will be a 20 amp for receps and 15 amps to lighting. You are right a 20 amp dedicated circuit is all that would be feasible.
 
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Old 04-06-10, 06:47 AM
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Just for thought a 5000 watt heater is just over 20 amps. (5000/240volts=20.83) It would require a 30 amp circuit though.
 
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Old 04-06-10, 10:45 AM
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Smile

Hey your right and with the 80% rule that would be 24 amps so indeed you would need a 30 amp. And yes THAT IS a hello of a heater 240 30amper (for a shed anyway.) also it will be cheaper on the bill being 240volts..

But the 60 amps aren't enough if you ask me as the subpanel will feed a small attached garage too.
It depends on what you will be using in there. Welder,air compressors, chop saw, etc..

For now it will be a 20 amp for receps and 15 amps to lighting. You are right a 20 amp dedicated circuit is all that would be feasible.
Where is the 20 amp coming from? If you got a 30 amp heater that leaves you with 2 15amps left on a 60amp sub. Or are you talking about a single dedicated 20 amp circuit that would not be feasible at all for what you are wanting..? Unless you just want a space heater, a radio, and a couple of lights.
 
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Old 04-06-10, 12:21 PM
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I think the 60 amp is right for him if he puts in a heater. If you think about it the building might be 15' x 20' a good size. Us guys love a space like this and there's so many tools out there on the market we can buy. Go for it and do it up right. Just remember you need 4 wires(2 hots, 1 neutral & 1 ground) going to the building and also install a ground rod.

Jim

 
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Old 04-06-10, 12:56 PM
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Originally Posted by SilverTattoo View Post
If you got a 30 amp heater that leaves you with 2 15amps left on a 60amp sub.
No, it can support a 30A 240V (7200W) heater, plus at least 4 15A 125V (1875W) circuits (assuming all at maximum). In practice, all the circuits are never maxed so that panel is capable of supporting the heater plus numerous general-purpose circuits for lighting, hand tools and stationary tools.

The only types of load that might really tax a 60A feeder is a heavy duty welder, plasma cutter or big milling machine -- the types of stuff that won't even really fit into a residential building.

The plan to install 60A will be more than enough for current and future needs.
 
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Old 04-06-10, 01:14 PM
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To add to this a 6 space panel does not require a main. I have wired more than a few garages where I usually feed with number 2 alum wire but put a 60 in the main panel, in 25 yrs, never, never, ever had one call with a tripped main from overload. Most people greatly over estimate the real demands. Most garage loads except for lights and in this case a heater or air cond are very intermittent, rarely even add any load demand to the house.
 
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Old 04-06-10, 03:07 PM
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silver your forgetting you can pull twice the amps on 240 than you can on 120... so he has 30 amps for the heater that isnt maxed out

plus 30 amps on each leg of 120 so he can run a whole (60 amps 120v) (30 amps 240v)worth of power tools and lights and not trip breakers

ben
 
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