Electricians advice needed

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I want to put a sub-panel in a connected garage. Can I use 6-ga. 3-wire to supply a panel with 4 breakers (20A each)? Do you have to consider the possible use of all of the circuits carrying the maximum load? Thanks!
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On 05/17/2016 08:57 PM, bob_villain wrote:

The determining factor is the breaker feeding the sub-panel
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If in the US you will need 4 wires, 2 hot, 1 neutral, 1 ground. You put in a breaker in the main panel and that determins the size of the wire you will need to use. At the sub panel you could most likely install 10 of the 20 amp breakers if you wanted to. You would not be able to use all of them at that current as the brakere at the main would trip first. Similar to most houses. If you total up all the breakers most likely they will be larger than the main breaker. Not many are going to use everything at once.
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On Tue, 17 May 2016 18:57:47 -0700 (PDT), bob_villain
You can if you put it on a 40 amp breaker --- You DO need a feed breaker for the panel.
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On Tuesday, May 17, 2016 at 9:15:25 PM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

So you're saying a 40A feed breaker and the sub panel can have 2 20A breakers?
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On Tue, 17 May 2016 20:06:14 -0700 (PDT), bob_villain

Yes if you are feeding it with a 2 pole 40 (240v) and you are using single pole branch circuit breakers (four 120v circuits)
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On Tue, 17 May 2016 20:06:14 -0700 (PDT), bob_villain

It can have 4. Look at your common 100 amp breaker panel - room for 32 breakers - even at 15 amps each, that's WAY over 100 amps. It's over 200.
Even if it's only an 18 slot panel - the range and drier alone acount fot 90 amps??? Add cental air for another 20.
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On Wed, 18 May 2016 00:49:02 -0400, snipped-for-privacy@snyder.on.ca wrote:

This looks like what the OP wants if he only wants 4 circuits It is 3R rated but you can use it inside. http://tinyurl.com/j4ehra8 http://www.homedepot.com/p/GE-PowerMark-Gold-40-Amp-2-Space-4-Circuit-Outdoor-Single-Phase-Main-Lug-Circuit-Breaker-Panel-TL240RCUP/100115114
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On Tuesday, May 17, 2016 at 11:49:06 PM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

Thanks...that was my assumption, but I wanted "clare"ification!
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wrote:

Don't you meed to run four wires?
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On Tue, 17 May 2016 21:36:50 -0500, "Dean Hoffman"

3 wire+ground - which a 6/3 cable contains.
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That's an odd thing on the terminology. We deal with 3 phase 480. The underground cable we bury is called quad. One wire is marked as the ground from the factory. #4 has all the wires the same size. Cable larger than that has the ground one size smaller than the other three.
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On Wed, 18 May 2016 05:27:39 -0500, "Dean Hoffman"

250.122 will allow a smaller grounding conductor in any cable larger than #10 (>30a O/C device) as a general rule. The regular #8-3 with ground will have a bare #10 in it for the EGC.
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On 05/18/2016 5:27 AM, Dean Hoffman wrote:
...

It's leftover from the pre required-grounding days in the Code when there was mostly (say) 14/2 or whatever and then there was 14/2 w/g which, of course, has three wires in the cable but couldn't call that 14/3 'cuz that was already taken for the case w/o ground and so on and so on...
If ground had been required from the git-go, common nomenclature would likely have been different and just counted the total number...
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On Tue, 17 May 2016 18:57:47 -0700 (PDT), bob_villain
It will be overkill if you are installing a 120/240 2/4 slot panel. That is 40a per phase as Clare said but you do need 3 wire plus ground (4 wires total) as Dean said. GE does make that 2/4 panel and I have seen it at about $14 each plus 4 skinny GE breakers.
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You do need to consider what the total load of the panel will be at any given time. Will you be running machines constantly or intermittently? You do not have to total up the rating of the individual circuit breakers.
You need four wires for a sub-panel and I think a ground rod for lightning protection is a good idea.
John Grabowski http://www.MrElectrician.TV
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On Thursday, May 19, 2016 at 7:01:18 PM UTC-5, John G wrote:

Thanks John, besides a circuit for fluorescent and LED lighting...there will be only one (table saw, miter saw, grinder, etc.) used at a time.
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On Thu, 19 May 2016 17:55:31 -0700 (PDT), bob_villain

If you do run that #6 in pretty much anything but Romex, (limited to the 60c column) you can hang a 60a breaker on it and put in a pretty nice sub panel. THHN in pipe would be an example of a wiring method that would get you into the 75c column (65a). At that point I would be looking at a 6 or 8 slot panel for a few bucks more than that 2/4 GE I linked the other day.
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On Thursday, May 19, 2016 at 9:25:00 PM UTC-4, snipped-for-privacy@aol.com wrote:

always better to go BIG when planning electrical upgrades. while up sizing may cost a bit more, its cheaper than upgrading later
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wrote:

"why is there always enough money to do something over, but never enough to do it right?"
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