141 volts on a phase 91 on b

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j98tt

Member
I narrowed it down to one circuit with a loose neutral but I cant find where on the circuit it is. The circuit is a lighting circuit with two sets of three ways and a total of 16 lights. I bypassed current wiring and switches with a jumper directly to lights. If I connect another light to the circuit I lose 2 volts take it away and I gain it back. I tried connecting directly from panel to the last light in the run and connected the other lights one by one and still the same problem I cant find this loose neutral can anyone help


thanks in advanced
 

j98tt

Member
the 141 and 91 is on the whole panel. When I turn of the lighting circuit the legs go back to normal.
 

brian john

Senior Member
Location
Leesburg, VA
You have a neutral issue (as noted ) before the point where you are measuring the strange voltage levels (as noted). The reason the lighting balances the voltage is it changes the impedance of the one phase giving the two phases a closely matched impedance's. With a series circuit(without the neutral you have a series circuit) two impedances of the same value will have the same voltage drop across them.
 
16 lights on one circuit. Thats alot of shift on one phase throwing the neutrals normal balance out of wack. Turn em on and check your voltage. If it is the 141 over 91 then check your Main Grounding Electrode Conductor for amps. Your neutrals amps will shift to the ground in order to complete the circuit. If this is the case either bad/loose neutral on the service feeder. Bad service lateral. Meter can issue (unlikely). Bad connection at the weather head. Or problem on utility end.
 
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480sparky

Senior Member
Location
Iowegia
.......If you cant pull your meter where you are at call the power company.

I wouldn't go that far. Turning the main off will accomplish the same thing.

Pulling the meter can cause two problems. Arcing, if it's under load, which it's not designed for. And in some cases, you may run afoul of the power company messing with their cash register.
 

OGuy

Member
Location
Livermore, CA
Call the Electric Utility

Call the Electric Utility

The electric utility is responsible for the electric system up to the panel. If there is a potential issue on their side, it is my experience that they will be eager to get out and check it before it becomes a loss claim.

The utility troubleman will probably have a device designed to check for a lose neutral connection. They utility I worked for would pull the meter and place a "Beast of Burden" on the service. It essentially placed a large resistive load on one leg and then the other. This makes a bad neutral condition apparent as the voltage changes. When the neutral is good, the voltage stays relatively stable.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
091229-2226 EST

j98tt:

Assuming the neutral problem is before or within the main panel, then you can do the following:

1. Equipment a good Fluke or equivalent digital voltmeter that can resolve 0.1 v at 120 V, and a 1500 W heater or hair dryer, about 12 A.

2. Make two portable outlets that can be connected to the two phases in the main panel. Do this thru two breakers in the panel from which you have removed their normal circuit.

3. Turn off all breakers in this panel except these two and the main breaker or fuses.

4. If the power company transformer is close by run a long wire to near its ground rod and connect to a screwdriver in the ground near the ground rod, maybe 6 ft away. This will be one test lead you will use in the experiments.

Otherwise put the screwdriver in the ground in line with the direction to the transformer as far toward the transformer as feasible. One or more extension cords make a good long test lead. Severe neutral problems may produce a large voltage between this probe wire and other points to which you measure voltage. Be careful.

5. With no load on the panel you should see nearly 0 volts difference between the probe lead from the transformer to the main panel neutral, its grounding electrode, and the water pipe. I would like to see 0 volts to mean something less than 0.25 V.

6. Next place the heater load between one hot leg in the panel and the panel neutral. What are the voltages of 5 now? This will depend upon the resistance of this path and the about 12 amps load.

Also measure the difference between the long probe lead and the neutral wire into the main panel from the meter. By wire I mean touch the wire and not the input lug. This eliminates a voltage drop at this main lug.

Depending upon the result from the tests determines the next action and likely points to where the problem may be.

The results may determine different measurements to make.

Some other simple measurements:

No load. In the main panel measure phase A bus bar to neutral bus bar, then the same from B. Next A to B. Apply the load from A to neutral and make the same measurements. And repeat from B.

.
 
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