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Old 08-21-2011, 12:36 AM   #16
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Wire Size Calculator Here, try this

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Old 08-21-2011, 01:01 AM   #17
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Oh and yet another question - I thought the ground wire was usually the same size as the hot and neturals. Why can I get away with a 10AWG instead of a 6AWG ground wire in this instance?
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Old 08-21-2011, 08:16 AM   #18
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Simple answer is that code allows you. Under normal conditions the ground does not carry any current, it only carries current when there is a problem and if the ground has something on it it will trip the breaker very quickly.
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Old 08-21-2011, 10:47 AM   #19
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If there is any possibility of running a pool or spa off this panel in the future, then use the green insulated ground.
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Old 08-21-2011, 11:31 AM   #20
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Why's that?
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Old 08-21-2011, 01:29 PM   #21
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The green will have to be insulated, you have to meet certain conditions when using a bare ground and you probably won't meet those.

Regarding your PM, I believe TWN can be run underground. We usually use RW90(which can go underground) and on the rare occasion we use T90 which can't go underground.

1" is good for 5 #6 RW90. You will only have three and a #8 ground. So 1" will be good but if it is a long run with lots of bends 1 1/4" will make pulling easier.

Your wire will have to be coloured as well, you won't be able to buy black and tape the ends to what you need.
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Old 08-21-2011, 01:57 PM   #22
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Quote:
Originally Posted by rjniles View Post
I will give you an answer for the USA but I believe it will also meet Canadian code. Run NM cable from the main panel (60 amp breaker) to a junction box above the trench. 1" PVC conduit from the house and terminated in a 100 amp main breaker panel in the garage. 3 runs of #6 THWN copper, 1 run of #10 bare or green. 2 ground rods bonded together to the ground bar in the sub. Separate ground and neutral bars in the sub.

There are other choices of cable and/or conduit, but I have given my preference.

Your discribing my setup almost exactly...except I used #6 THHN (I had a bunch already), #10 bare ground....feeding it with a 50a breaker in my 200A load center on the house....going through 1" PVC conduit.

Note...per the NEC, you can't have more than 6 breakers unless you have a main breaker in your sub panel.

If you don't need a ground rod...fine....but I pretty sure you would NOT bond your earth ground to your neut in your sub panel. They only get connected together in your main panel.

As for current....I was feeding my garage with 30A....NEVER tripped the main breaker...at most I have the air compressor and one tool running along with a radio.....and maybe all the lights....

Look at your loading....figure out what the abosolute max # of items you might have on at the same time. If your like me, you only use one tool at a time...50a should be more than enough. Over that and those #6 awg's will not be big enough.....and #4 might start to get a bit tight in that 1" conduit for the run...iut will fit....but if you have too many bends....it can get tough.

Click on the link in my signature to see my garage build. It sounds like your doing something close to what I did.
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Old 08-21-2011, 02:21 PM   #23
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Quote:
Originally Posted by ddawg16 View Post
Your discribing my setup almost exactly...except I used #6 THHN (I had a bunch already), #10 bare ground....feeding it with a 50a breaker in my 200A load center on the house....going through 1" PVC conduit.

If you used THHN, it is not rated for use in conduit. However most wire is dual rated THHN/THWN today

Note...per the NEC, you can't have more than 6 breakers unless you have a main breaker in your sub panel.

Not exactly true. The requirement is no more than 6 handle motions to turn off all circuits. You can use handle ties to meet this requirement and have more than 6 breakers. But having a main breaker in the sub is better way to go IMO.

If you don't need a ground rod...fine....but I pretty sure you would NOT bond your earth ground to your neut in your sub panel. They only get connected together in your main panel.

Definitely, ground and neutral separate in the sub panel
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Old 08-21-2011, 03:12 PM   #24
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Sounds good guys, you've all given me plenty to work with. Trench was put in this morning, picked up 1 1/4" rigid conduit (went with the larger size for easier pulling like you guys mentioned). As soon as I'm done typing I'm heading out to run the piping. I'll followup with the city tomorrow to see what types of wire/cables they allow underground in my municipality.
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Old 08-21-2011, 03:28 PM   #25
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I'm sure that rjniles didn't mean to say that THHN is not rated for use in conduit, because it is......but it's not rated for WET locations.
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Old 08-21-2011, 04:08 PM   #26
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Quote:
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I'm sure that rjniles didn't mean to say that THHN is not rated for use in conduit, because it is......but it's not rated for WET locations.
Yes, I meant buried conduit (a wet location). Sorry about the mental lapse.
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Old 08-21-2011, 08:20 PM   #27
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Mental lapses are part of my daily routine. You are not alone.
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Old 08-21-2011, 10:12 PM   #28
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Can the LB be used as a junction box to switch wire types at the house?
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Old 08-21-2011, 10:14 PM   #29
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The LB is also a JB
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Old 08-21-2011, 10:37 PM   #30
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Great! Do you have a reference to box fill for this? My electrical code simplified only has fill charts for interior boxes.

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