Wiring from Main House to Garage Sub-Panel

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Old 03-21-14, 09:25 AM
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Wiring from Main House to Garage Sub-Panel

The Current Situation:
I have a 30 amp breaker in the main panel in the house. This is currently feeding 110 to a sub-panel in the garage. The garage sub-panel currently houses 3 single-pole breakers (1 15-amp and 2 20amp)

The Future Situation:
I want to upgrade the breaker in the main panel to a 60-amp breaker to feed the sub-panel in the garage. I also want to run new wire to carry 220 to the sub-panel in the garage. I want to install a 30-amp dual-pole breaker in the garage sub-panel to bring power to a cadet heater and an outlet.

The distance of wire I'm going to need between the house and the garage panels is going to be 70'. What gauge of wire will I need to span this distance?
 
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Old 03-21-14, 09:39 AM
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If we assume that the garage is attached to the house.......

With the addition of a two pole 60A breaker you'll need to run 6-3 w/gr NM or MC type cable between the main panel and the sub panel.
 
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Old 03-21-14, 09:44 AM
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The garage is not attached to the house. However, part of the run is under the house in a crawlspace and the remainder of the run is through schedule 40 conduit, so the wire is never in an exterior condition.

I assumed that there is a voltage drop over that large of a distance which would require an increase in wire gauge.
 
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Old 03-21-14, 12:41 PM
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Conduit outside is considered a wet location no matter how well sealed so just run THWN all the way in conduit. Running cable in conduit is no necessary except for example for short sleeves to protect it where it enters and leaves the ground. One hundred feet or less no need to worry about voltage drop.
 
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Old 03-21-14, 12:45 PM
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So is PJ's suggestion of 6ga wire going to be sufficient?
 
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Old 03-21-14, 06:55 PM
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So is PJ's suggestion of 6ga wire going to be sufficient?
Yes, but not NM or MC cable. If you use cable it must be UF cable, but I'd do like Ray suggested and run THWN conductors in conduit all the way. You'll need 3 - #6s and 1 - #10 ground. You'll need to add an auxilliary ground bar in the subpanel and install one or two ground rods at least 6 feet apart and connect them to the ground bar with #6 copper, bare or insulated. I prefer bare. The neutral bar should not be bonded to the box and only neutral wires terminate on the neutral bar. The ground wires will terminate on the ground bar.
 
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Old 03-21-14, 07:32 PM
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Depending on the size of the conduit you may not be able to upgrade the feeder.

Also that is a split bus panel the bottom section is limited to most likely 60 amps.
 
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Old 03-22-14, 02:47 PM
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So, in this application is it necessary to run 4 individual wires or am I able to use a cable such as this:

#6-3 THHN-PVC Tray Cable with Ground
 
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Old 03-22-14, 03:33 PM
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That is a special purpose cable. You would use UF-b. Best practice is not to run UF-b in conduit except for short sections to protect it such as when it enters and leaves the ground.
 
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Old 03-22-14, 07:47 PM
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So, in this application is it necessary to run 4 individual wires or am I able to use a cable such as this:

#6-3 THHN-PVC Tray Cable with Ground
That tray cable is also approved for direct burial. When tray cable is the cheapest option, there is usually a catch.
 
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Old 03-22-14, 09:38 PM
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When tray cable is the cheapest option, there is usually a catch.
Looked like 3-phase without a neutral and since #6 can't be remarked that could be the catch.
 
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