neutral to ground voltage
- Thread starter mrwoo1981
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: neutral to ground voltage
Is this circuit fed from a subpanel? The only voltage that should appear between the equipment grounding conductor and the grounded conductor is the voltage drop on the grounded conductor between the main bonding jumper and the point where you are reading the voltage. If the circuit originates in the service disconnect then there should be no voltage between the EGC and the grounded conductor if there is no load on that grounded conductor.
Don
Is this circuit fed from a subpanel? The only voltage that should appear between the equipment grounding conductor and the grounded conductor is the voltage drop on the grounded conductor between the main bonding jumper and the point where you are reading the voltage. If the circuit originates in the service disconnect then there should be no voltage between the EGC and the grounded conductor if there is no load on that grounded conductor.
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: neutral to ground voltage
There are three ways to solve the problem, 1) increase the size of the grounded conductor in the panel feeder, 2) reduce the load on the grounded conductor to the panel, or 3) install a transformer and create a new grounded to grounding bonding point.
Don
There are three ways to solve the problem, 1) increase the size of the grounded conductor in the panel feeder, 2) reduce the load on the grounded conductor to the panel, or 3) install a transformer and create a new grounded to grounding bonding point.
Don
Re: neutral to ground voltage
mrwoo, since this is being fed from a sub-panel, I doubt your going to be able to keep the N-G voltage from exceeding 2 volts with oversizing the neutral conductors. Measure the voltage at the sup-panel between N-G and see how much voltage you have to work with.
If it is below 1 volt you might get away with using a dedicated branch circuit with an oversized neutral. If not your only option is an isolation transformer.
Please do not do as some manufactures suggest to bond the neutral to ground at a downstream panel to achieve this goal.
Dereck
[ September 26, 2003, 11:45 PM: Message edited by: dereckbc ]
mrwoo, since this is being fed from a sub-panel, I doubt your going to be able to keep the N-G voltage from exceeding 2 volts with oversizing the neutral conductors. Measure the voltage at the sup-panel between N-G and see how much voltage you have to work with.
If it is below 1 volt you might get away with using a dedicated branch circuit with an oversized neutral. If not your only option is an isolation transformer.
Please do not do as some manufactures suggest to bond the neutral to ground at a downstream panel to achieve this goal.
Dereck
[ September 26, 2003, 11:45 PM: Message edited by: dereckbc ]
brian john
Senior Member
- Location
- Leesburg, VA
Re: neutral to ground voltage
Of course you could ask them where and why they determined this level was a determent to their equipment. The most likely pulled it out of someone else's spec, and have no clue whether this level of N/gnd voltage would really cause a equipment operational problems.
Of course it also gives them an out, should their equipment screw up.
A bit cynical, but I have seen so many manufacture specs stating all kinds of N/GND specs from .5 vac and up. The .5 spec was supplied in a letter to a customer. A piece of equipment would not operate properly. The manufacture tech measured .75 volts N/gND and the letter followed.
I suggested a isolation transformer at the point of use and Walla the equipment still did not work. The next letter, stated the transformer was improperly grounded, then too small, then not a proper installation for this type of equipment, finally the manufactured fixed the equipment (software problem) but never admitted the problem.
Of course you could ask them where and why they determined this level was a determent to their equipment. The most likely pulled it out of someone else's spec, and have no clue whether this level of N/gnd voltage would really cause a equipment operational problems.
Of course it also gives them an out, should their equipment screw up.
A bit cynical, but I have seen so many manufacture specs stating all kinds of N/GND specs from .5 vac and up. The .5 spec was supplied in a letter to a customer. A piece of equipment would not operate properly. The manufacture tech measured .75 volts N/gND and the letter followed.
I suggested a isolation transformer at the point of use and Walla the equipment still did not work. The next letter, stated the transformer was improperly grounded, then too small, then not a proper installation for this type of equipment, finally the manufactured fixed the equipment (software problem) but never admitted the problem.
Re: neutral to ground voltage
I do have to ask one question: How are you measuring the voltage? With your ultra high impedence Fluke? If so, try an analog meter and see if it's really there. Unless they gave you a very detailed spec, it should be your choice of what meter to use.
I do have to ask one question: How are you measuring the voltage? With your ultra high impedence Fluke? If so, try an analog meter and see if it's really there. Unless they gave you a very detailed spec, it should be your choice of what meter to use.
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