Electrical wiring question

[bdog]

I am adding a sub panel. I am going to add six 110v outlets each with their own 15 amp breaker. Each outlet will have a constant load of about 12 amps.

My plan was to run 6/3 from the main panel on a 50A breaker to the sub panel. Distance is about 50'. At the sub panel I was going to run three outlets on one leg and three on the other. 12 ga for the outlets. 6 ga is rated for 55 amps.

My question is the 6ga can handle the load on the hot legs no problem but what about the neutral? Can a single 6ga neutral handle a continuous 36 amp 120 load on both legs? Since the legs are out of phase I am not sure. Will the neutral be seeing 72 amps and burn up or will it see very little load since the two legs feeding it are nearly balanced and out of phase?

 

[Gordon Gould]

The 6 Ga neutral to the sub panel only has to handle the imbalance currant between the two 120V legs.

gg

 

[CincyFlyer]

If you have a constant 12-amp load, make sure that your 15-amp breakers don't pop on the inrush (depending on what you are running)!

 

[CobyRupert]

The 6 Ga neutral to the sub panel only has to handle the imbalance currant between the two 120V legs.

gg

:thumbsup:

The most it can be out of balance, and thus the most the neutral would ever see is 36 amps. (Basically the maximum that one phase can see.) This would occur if all the loads on one phase were off when all the other phase loads are on.
Conversely, the closer the phase loads get to being balanced, the closer the neutral current gets to zero.

Also remember:
A sub-panel in another building needs it's own ground electrode (ground rod), in addition to the ground conductor you bring from the main panel. And:
You should NOT bond the (white) neutrals (or neutral bar) with the (green) grounds (or ground bar, or panel enclosure) in the sub-panel. The neutrals should be isolated (from the ground) in the subpanel.
This bonding should only be done in one place. (Usually at your main service panel, or first service disconnect if one is upstream of main panel)

 

[Zebrafive]

One other thing to check is if code requires a main breaker in your sub panel. I know there is no "need" for one, BUT where I'm located, if you have more than 6 circuits, a main breaker is required in the sub panel. So if you are considering more than 6 circuits, consider a sub panel with a main breaker.

 

[buickanddeere]

If there is 3 x 12 amps on line 1 and 3x12amps on line 2. Neutral current will be zilch, zero nada .

 

[aeblank]

A sub-panel in another building needs it's own ground electrode (ground rod), in addition to the ground conductor you bring from the main panel.

I am fairly confident this is *not* true. We did that, and my inspector made us disconnect/tape off one or the other (cannot remember for sure which, but I'd bet on it being the ground rod). I'd be asking the inspector about this one.

You should NOT bond the (white) neutrals (or neutral bar) with the (green) grounds (or ground bar, or panel enclosure) in the sub-panel. The neutrals should be isolated (from the ground) in the subpanel.
This bonding should only be done in one place. (Usually at your main service panel, or first service disconnect if one is upstream of main panel)

I believe this to be true though and agree with this. Ground loops/radio hum/etc.

 

[bdog]

Thanks guys.

I seemed to remember this was the case but wasn't sure.

The panel will be in my house, not a separate building so no additional ground rods needed and the ground and neutral will remain isolated.

The load is 12 amps max and should not exceed that or have a high startup. It is all computers - specifically bitcoin miners.

 

[hawkeye08]

Thanks guys.

I seemed to remember this was the case but wasn't sure.

The panel will be in my house, not a separate building so no additional ground rods needed and the ground and neutral will remain isolated.

The load is 12 amps max and should not exceed that or have a high startup. It is all computers - specifically bitcoin miners.

Let us know if you strike it rich... tell us how you did it.

 

[bdog]

I think the ship has sailed on getting rich from them but they are still a viable investment I think. An approximate 2k investment in a miner should yield about $500 a month in bitcoin at current prices and will consume about $100 a month in electricity for $400 net. Should pay for itself in about 5 months and then after that give you $400 a month profit. Of course this all assumes the prices and mining difficulty stay similar to what they are now.

I certainly don't want to bet the farm on it but I am going to run six of them and see what happens.

The early adopters won the lottery if they managed to keep their coins until now. Back in 2009/10 a basic household desktop computer could mine around 25 bitcoins a day. At today's prices that would be over 100k a day!! If you ran it for a year back then on your regular old computer and kept the coins until today they would be worth 36 million dollars.