branch cicuits

[iloveskydiving]

I see alot of shared commons (1 white) with 2, 120 volt circuits.If they are loaded up to 80 percent then you have a problem with to many amps on the shared common. Why is this allowed, I see the white insulation starting to turn brown and getting overheated.?????:-?

 

[roger]

I see alot of shared commons (1 white) with 2, 120 volt circuits.If they are loaded up to 80 percent then you have a problem with to many amps on the shared common.

Not true if these are neutrals.

If they are only shared grounded conductors (both circuits on the same leg or phase) the "common" conductor should be sized for the max amps that may be imposed on it. BTW, they can be loaded to 100% for 179 min 59 sec.

Why is this allowed, I see the white insulation starting to turn brown and getting overheated.?????:-?

Most likely to small of a conductor for the combined load of both circuits. The solution is to put the ungrounded conductors on opposite legs or different phases.

Roger

 

[Dennis Alwon]

The solution is to put the ungrounded conductors on opposite legs or different phases.

Roger

Or tighten the neutral wire it may be loose.

As Roger has said if this is a MWBC -- one grounded conductor with two ungrounded conductors , and they are connected on opposite phases, then this should not be an issue. If the ungrounded conductors are on the same phase you can overload the grounded conductor.

On a MWBC the grounded conductor only carries the unbalanced load. Thus if one ungrounded conductor was connected to a 10 amp lamp and the other ungrounded conductor was connected to a 10 amp load then the grounded conductor (neutral in this case) will carry 0 amps.

If those same ungrounded conductors were hooked to the same phase then the grounded conductor would carry 20 amps.

 

[480sparky]

Sounds like you don't have a true multi-wire branch circuit. Both hots are on the same leg or phase, so the neutral carries the sum of the amperages.

BTW, welcome to the forum!

 

[cloudymacleod]

Not true if these are neutrals.

If they are only shared grounded conductors (both circuits on the same leg or phase) the "common" conductor should be sized for the max amps that may be imposed on it. BTW, they can be loaded to 100% for 179 min 59 sec.

Most likely to small of a conductor for the combined load of both circuits. The solution is to put the ungrounded conductors on opposite legs or different phases.

Roger

with two circuits shared by the same netrual on the same phase/leg, wouldn't the amps add up on the netrual coming back to the source, creating a hazard? and is it legal to share neutrals with circuits being on the same phase/leg.

 

[480sparky]

with two circuits shared by the same netrual on the same phase/leg, wouldn't the amps add up on the netrual coming back to the source, creating a hazard? and is it legal to share neutrals with circuits being on the same phase/leg.

Yes and no, in that order.

 

[roger]

Yes and no, in that order.

First we have to understand that the term "neutral" doesn't apply in this situation and with that said, I disagree with answer # 2 as a blanket statement, a shared neutral is specifically allowed in 225.7(B)

Roger

 

[cloudymacleod]

First we have to understand that the term "neutral" doesn't apply in this situation and with that said, I disagree with answer # 2 as a blanket statement, a shared neutral is specifically allowed in 225.7(B)

Roger

but 225-7 deals with outside lighting equipment and grounded/common/white means they r talking about the neutrals, so i would say neutrals do apply. but in my last message i was just wondering is it legal by code to have 2 circuits on the same phase/leg to share a neutral, my thought the answer would be no because i would think it could cause a hazard down the line? to me a multi-wire branch circuit is the same term if some one questions shared neutrals, but i could be wrong.

 

[roger]

but 225-7 deals with outside lighting equipment and grounded/common/white means they r talking about the neutrals, so i would say neutrals do apply.

And yes they do, even if the conductor is a neutral and carries the load of more than one circuit on the same leg or phase. Now, where is it prohibited for inside circuits?

but in my last message i was just wondering is it legal by code to have 2 circuits on the same phase/leg to share a neutral,

Yes it is.

my thought the answer would be no because i would think it could cause a hazard down the line?

Not if the conductor is sized for the load.

to me a multi-wire branch circuit is the same term if some one questions shared neutrals, but i could be wrong.

A MWBC would see zero amps if the loads on both circuits of a single winding are equal.

Roger

 

[Lxnxjxhx]

would see zero amps

would see zero amps

And in this case you can remove the neutral without affecting the rest of the circuit.

 

[iloveskydiving]

Electrician

Electrician

thanks to everyone that replied to my question, they helped alot and I'll be going back to do some more checking.........:wink: