Single Phase Resi-W/One Leg down approx. 10vac

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2BEARS

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Joshua tree CA USA
I'm Sure there's an answer I'm overlooking...But First off, 60's Zinsco Main Panelboard Gotta Go. Regardless, I Have A Single Phase Resi-System With One Phase Down Approximately 10vac-AND if I Turn off a certain 30amp 2 pole, (to an unspecified load) The One Phase in Question Drops Out Completely. Any Info Appreciated.
Voltages @ Load Side of Meter o.k.-Voltages Out of 100amp Main Service Disconnect To Busses o.k.
 
2BEARS said:
I'm Sure there's an answer I'm overlooking...But First off, 60's Zinsco Main Panelboard Gotta Go. Regardless, I Have A Single Phase Resi-System With One Phase Down Approximately 10vac-AND if I Turn off a certain 30amp 2 pole, (to an unspecified load) The One Phase in Question Drops Out Completely. Any Info Appreciated.
Voltages @ Load Side of Meter o.k.-Voltages Out of 100amp Main Service Disconnect To Busses o.k.
Click to expand...
The most likely cause is that one incoming service wire (call it L2) is open somewhere (either on POCO side or in customer wiring) and the voltage that you read on L2 in the panel is actually voltage from L1 which is feeding through the 240V load connected to the 30A breaker. That 240V load will not be working properly, since it is seeing only 10V of voltage between its two terminals. If it is a motor load, it will not be happy! If it is a resistive load (like a water heater or electric space heater) then it will not be damaged, but it will not work right either.
 
Thank You Gold digger. It is, I Believe in the clients wiring. I have Correct Voltage In & Out Of Main Brkr.(*Bad Phase Connection to Buss Bar from Main Breaker?Or?)
The 30amp 2 pole Of course is not labeled...one would expect, W/H-Small AC etc...But, when de-energized
Receptacles drop out. Also applying load to circuit in one rooms receptacle, makes a lamp in same room on another receptacle turn On. This to me screams loose Neutral(s)? This Symptom doesn't seem to be related. Wouldn't a Dropped L2 Just Mess With 240 loads.
 
2BEARS said:
Thank You Gold digger. It is, I Believe in the clients wiring. I have Correct Voltage In & Out Of Main Brkr.(*Bad Phase Connection to Buss Bar from Main Breaker?Or?)
The 30amp 2 pole Of course is not labeled...one would expect, W/H-Small AC etc...But, when de-energized
Receptacles drop out. Also applying load to circuit in one rooms receptacle, makes a lamp in same room on another receptacle turn On. This to me screams loose Neutral(s)? This Symptom doesn't seem to be related. Wouldn't a Dropped L2 Just Mess With 240 loads.
Click to expand...
A loose neutral will potentially deliver far more than 120V to some loads. And the sum of the L1-N voltage and the N-L2 voltage will remain constant at or near 240V while the L1 and L2 voltages vary.
An open L2 will mean that not only 240V loads but also any 120V loads connected between L2 and N will not work. (Which you see when the 30A breaker is open.)
 
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