Piggy Back

Status
Not open for further replies.
M

mac380abc

Member
Location
06074
Occupation
Electrical Engineer also E-1
I believe I know the answer, but I would like another opinion. on a 120/208 circuit breaker panel, I have a single breaker with 2 breakers on it.
If I install two wires from the same service to the twin breaker, does the neutral see the entire load of both wires,? Instead of the imbalance
of the 2 lines? If I am drawing 10 amps on one leg and 5 amps on the other, would it be 15 amps on the neutral or 5 amps on the neutral?

Thank you for the feed back..
 
So you have a single "slot" and a twin or piggy-back style breaker occupying the single slot providing two circuits?

Welcome to the Forum. :)
 
General electric 1" 2-pole breakers are easily confused with 1" 1-pole twins in the same load center.
 
mac380abc said:
I believe I know the answer, but I would like another opinion. on a 120/208 circuit breaker panel, I have a single breaker with 2 breakers on it.
If I install two wires from the same service to the twin breaker, does the neutral see the entire load of both wires,? Instead of the imbalance
of the 2 lines? If I am drawing 10 amps on one leg and 5 amps on the other, would it be 15 amps on the neutral or 5 amps on the neutral?

Thank you for the feed back..
Click to expand...
If both loads are on the same line, 15A; If One is on Line 1 and the other is on Line 2, 5A.
 
ggunn said:
If both loads are on the same line, 15A
Click to expand...
Yes, assuming equal power factor.

ggunn said:
If One is on Line 1 and the other is on Line 2, 5A.
Click to expand...
No, that would be correct for a 120/240V system (again assuming equal power factor), but the OP specified a 208Y/120V system. In which case, the two currents will be 120 degrees apart. So the magnitude of the vector sum will be sqrt(10^2 + 5^2 + 2 * 5 * 10 * cos 120) = 8.66A.

Cheers, Wayne
 
mac380abc said:
I believe I know the answer, but I would like another opinion. on a 120/208 circuit breaker panel, I have a single breaker with 2 breakers on it.
Click to expand...
Welcome to the forum.

If it's a typical tandem breaker, the two circuits should not share a neutral.
 
wwhitney said:
Yes, assuming equal power factor.


No, that would be correct for a 120/240V system (again assuming equal power factor), but the OP specified a 208Y/120V system. In which case, the two currents will be 120 degrees apart. So the magnitude of the vector sum will be sqrt(10^2 + 5^2 + 2 * 5 * 10 * cos 120) = 8.66A.

Cheers, Wayne
Click to expand...
Sorry; I missed the 208/120V
 
infinity said:
So you have a single "slot" and a twin or piggy-back style breaker occupying the single slot providing two circuits?

Welcome to the Forum. :)
Click to expand...
That is correct, and if I used a common neutral. Would the load be 30A if they are both pulling 15 Amps each, or would they cancel, Seems that
all neutrals are bonded to the same neutral bar. What Im looking to do is bring 2 15Amp circuits over using a piggyback breaker with a cable
that has red , black, white and green ,
ggunn said:
If both loads are on the same line, 15A; If One is on Line 1 and the other is on Line 2, 5A.
Click to expand...
Thank you for the reply, That is what I had thought; although my question is if I draw 10 amps on one of the breakers and 15 on the other
that would mean the neutral would see 25 amps, and would that be rated as code compliant lets say for a #12 wire.
 
mac380abc said:
That is correct, and if I used a common neutral. Would the load be 30A if they are both pulling 15 Amps each, or would they cancel, Seems that
all neutrals are bonded to the same neutral bar. What Im looking to do is bring 2 15Amp circuits over using a piggyback breaker with a cable
that has red , black, white and green ,

Thank you for the reply, That is what I had thought; although my question is if I draw 10 amps on one of the breakers and 15 on the other
that would mean the neutral would see 25 amps, and would that be rated as code compliant lets say for a #12 wire.
Click to expand...
You cannot use a common neutral for two circuits on the same phase. If you want to use a piggy back CB you'll need separate neutrals.
 
Status
Not open for further replies.
Top