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Old 02-03-2009, 12:46 PM   #16
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A 30a 240v would give you quite a bit of power too
That would give you 60a @120v - maybe that is what you were thinking of with the 10-3?
I haven't run any 30a 240v that distance, not sure on the exact wire size needed
But I thought #10 was rated for 30a

But #10 at 130' = voltage drop of 7.8% = too high
#8 gives you 4.9% voltage drop

But if I'm up to #8 already I'd just go to #6 - 3.1% voltage drop

I've asked my share of dumb questions
Its the only way I learn

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Old 02-03-2009, 01:25 PM   #17
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That would give you 60a @120v
Here we go again

You don't do the math like that
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Old 02-03-2009, 01:34 PM   #18
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60 amp on 120? My 320/400@240v service is really a 640/800@120!

Talk about power!

No really, you have a 30 amp mwbc, one leg can pull 30 and the other, 30. L1-L2 is still 30, but at 240v.

If both legs were evenly balanced the neutral would see 0 amps.

Last edited by rgsgww; 02-03-2009 at 01:37 PM.
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Old 02-03-2009, 02:14 PM   #19
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Here we go again

You don't do the math like that
30a on each leg......??
I'm sorry, is there something wrong with that????
I should have pointed that out
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Old 02-03-2009, 02:41 PM   #20
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30a on each leg......??
I'm sorry, is there something wrong with that????
I should have pointed that out
Dave.. I think I know what your saying but it is incorrect to say you have 60A available. You have 30 amps available with a double pole 30 amp breaker. You have 60 amps available with a 60 amp double pole breaker. You do have twice the power available however... as you are delivering 2 120 volt circuits using a common neutral.

30 amps x 120 volts = 3600 watts
30 amps x 240 volts = 7200 watts

Point is that if either leg of a 30 amp double 120/240 volt circuit draws over 30 amps the breaker will trip out. So there really is only 30 amps at 120 volts available times 2 in watts.

I'm interpreting what your saying as there is twice the power available.

These other guys just don't understand your lingo......
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Old 02-03-2009, 02:49 PM   #21
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Yeah, I just didn't explain it right
But as I understand it I could draw 29.9999a on each leg without a problem = equal almost 60a at 120v

I know that most people might not balance the load that way
But I use a meter to setup my Christmas display electric
All the Christmas geeks calc in 120v power available
It's just the way I calculate it - since my Christmas display takes 80a @ 120v

And I don't kick out the 60a breaker
So to say I will kick out the breaker the minute I exceed 60a is not quite true. Saying if either leg exceeds 60a is (in my case I have a 60a 240v panel)
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Old 02-03-2009, 02:56 PM   #22
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But as I understand it I could draw 29.9999a on each leg without a problem = equal almost 60a at 120v
Carry on Dave I know exactly what you mean.....
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Old 02-03-2009, 03:14 PM   #23
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hi,

ok, i think i understand the 2 pole breaker info. i have a electric in wall heater that is 240vac 1500 watts, that is run off a 2 pole 20amp breaker, using 12-2 romex, hence, 120vac, 20amp, per leg, and is only drawing 6.25 amps, which is a good measure below the 16 amp rating use for a 20 amp breaker, correct?...bob
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Old 02-03-2009, 05:39 PM   #24
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I think thats 10 amps per leg and you mean 12/3 right plus ground??
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Old 02-03-2009, 06:12 PM   #25
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You can run #10 THHN/THWN's in the 1 inch conduit. { 30 amp double pole breaker }

I know you will say 1 inch ??? keep in your mind the reason why I suggest in the conduit due once you buried the conduit you don't have to redig it again to put in larger conduit at all.

The one inch conduit will handle #6 THHN/THWN's without effort in there { it is sized to take #4's in worst case senireco }

I done this more than few time and few years later that customer called me up to upgrade the subpanel all i just yank old conductors out and put in larger conductors and installed correct breaker size and be done with it.

I know the Conduit will cost little more on one inch size but it worth it and also a nice tip along the way if you going to bury the conduit get a half inch in there as well so that way you have either phone or internet hook up as well.

The other tibbit some of the reader may overlook on subpanel there is a 6 throw rules so if you have 6 breakers or less you don't need a main breaker in subpanel but if you plan have more than 6 then install the main breaker or get main breaker box { sometime it cheaper to just buy the main breaker box than main lugs (without main breaker ) box is }

Merci,Marc
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Old 02-03-2009, 08:39 PM   #26
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I think thats 10 amps per leg and you mean 12/3 right plus ground??
no. its romex 12-2, plus ground. i always thought it was 12=ga, 2=conductors, and ground was just taken for granted. its black, white, and bare ground, running from a 2 pole 20amp breaker. thats why i assumed, that each leg would be 120vac, 20amp, because of the 12ga wire...bob
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Old 02-03-2009, 08:53 PM   #27
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Originally Posted by bobo60 View Post
no. its romex 12-2, plus ground. i always thought it was 12=ga, 2=conductors, and ground was just taken for granted. its black, white, and bare ground, running from a 2 pole 20amp breaker. thats why i assumed, that each leg would be 120vac, 20amp, because of the 12ga wire...bob
NO, each leg is NOT 120v because there is no neutral present to give you 120v. That is simply a 240v circuit.
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Old 02-03-2009, 10:43 PM   #28
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NO, each leg is NOT 120v because there is no neutral present to give you 120v. That is simply a 240v circuit.
speedy,

i put a dmm across white and black and got 240vac. i measured between black and ground, or white and ground and got 120vac. so whats up with that?..bob
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Old 02-03-2009, 10:52 PM   #29
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240v devices do not need a white neutral wire
Usually they use a normal 12-2 & the white wire is remarked hot
So you have (2) 120v feeds for a 240v device
But you do not have a 120v setup as you need a neutral wire for a true 120v connection

If the white is not remarked black then it should be IF it is connected to the hot on a double pole breaker

You are reading 120v, but in this case its part of a 240v setup

I think (hope) that makes sense ??
Anyone? Beuhler ?
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Old 02-03-2009, 11:11 PM   #30
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[quote=Scuba_Dave;224780]240v devices do not need a white neutral wire
Usually they use a normal 12-2 & the white wire is remarked hot
So you have (2) 120v feeds for a 240v device
But you do not have a 120v setup as you need a neutral wire for a true 120v connection

If the white is not remarked black then it should be IF it is connected to the hot on a double pole breaker

You are reading 120v, but in this case its part of a 240v setup

I think (hope) that makes sense ??
Anyone? Beuhl

i still dont quite understand.. i know that you need to have a neutral, so you can get 120vac to run the clock, timer, etc... on an electric stove, so how does it differ for the heater i spoke of?....bob


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