A large department store in my hometown was told by a satellite TV tech they had 2.5 vac from neutral to ground and that was what was messing up the receiver they installed in the UPC room. The receiver is located in a rack with computer equipment and there are power strips to plug into. I checked the receptacle on the power strip and there was .1 vac ground to neutral but when the power cord to the receiver is plugged in I read 2.5 vac ground to neutral. A wall receptacle nearby had .1 vac and we thought about tapping off it but checked it later there was 3.1 vac at the receptacle itself. This problem seems to come and go. Can anyone tell me how to solve it? Thanks.
voltage from egc to neutral
- Thread starter ghelec
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: voltage from egc to neutral
When you check the voltage between the EGC and the neutral, you are really measuring the voltage drop on the neutral between the point of measurement and the main bonding jumper. This can be caused by excessive neutral current, or more likely in this case, a poor connection on the neutral.
Don
When you check the voltage between the EGC and the neutral, you are really measuring the voltage drop on the neutral between the point of measurement and the main bonding jumper. This can be caused by excessive neutral current, or more likely in this case, a poor connection on the neutral.
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: voltage from egc to neutral
The problem could be anywhere in the circuit. I don't know why is shows up in one place and the other. You just have to work the complete circuit to find the problem.
Don
The problem could be anywhere in the circuit. I don't know why is shows up in one place and the other. You just have to work the complete circuit to find the problem.
Don
Re: voltage from egc to neutral
Don, I went back to the store today and checked all JB's and in the panel. I did not find any loose neutrals or grounds. When I got there I checked and there was 18 VAC ground to neutral where the satellite receiver is plugged in and the other recept. in the UPC room which is on a different circuit had 4 VAC on it. The way this comes and goes is there the possibility of some appliance or equipment in the store causing this? The satellite tech wants a dedicated circuit ran but I wonder if that would help. If I spent the time and materials to run a dedicated circuit and it did not correct the problem they would probably not want to pay and I would have to eat it which I do not want to do. Any other ideas.
Don, I went back to the store today and checked all JB's and in the panel. I did not find any loose neutrals or grounds. When I got there I checked and there was 18 VAC ground to neutral where the satellite receiver is plugged in and the other recept. in the UPC room which is on a different circuit had 4 VAC on it. The way this comes and goes is there the possibility of some appliance or equipment in the store causing this? The satellite tech wants a dedicated circuit ran but I wonder if that would help. If I spent the time and materials to run a dedicated circuit and it did not correct the problem they would probably not want to pay and I would have to eat it which I do not want to do. Any other ideas.
- Location
- Illinois
- Occupation
- retired electrician
Re: voltage from egc to neutral
Does the service have a main bonding jumper? Are there EGCs or is a raceway used as the grounding conductor? Does a "wiggy" show voltage between the hot and the EGC?
Don
Does the service have a main bonding jumper? Are there EGCs or is a raceway used as the grounding conductor? Does a "wiggy" show voltage between the hot and the EGC?
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: voltage from egc to neutral
Are these circuits fed from a SDS?
Don
Are these circuits fed from a SDS?
Don
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Re: voltage from egc to neutral
[ February 28, 2006, 05:16 AM: Message edited by: infinity ]
Is the shield on the satellite cable grounded? I thought that satellite receivers had an output of about 18 volts.
[ February 28, 2006, 05:16 AM: Message edited by: infinity ]
- Location
- Illinois
- Occupation
- retired electrician
Re: voltage from egc to neutral
Don
[ February 28, 2006, 06:49 AM: Message edited by: don_resqcapt19 ]
Yes, see 250.148.
Yes
Tested with a digital meter or a solenoid voltage tester?
Don
[ February 28, 2006, 06:49 AM: Message edited by: don_resqcapt19 ]
Re: voltage from egc to neutral
The coax had voltage on it when I first started but I grounded it. I am using a digital meter. I was surprised to find the EC did not bond the JB's,they were from the city,thought they would have known code. This runs 150-200 feet from panel to UPC room. Can this be induced voltage?
The coax had voltage on it when I first started but I grounded it. I am using a digital meter. I was surprised to find the EC did not bond the JB's,they were from the city,thought they would have known code. This runs 150-200 feet from panel to UPC room. Can this be induced voltage?
- Location
- Illinois
- Occupation
- retired electrician
Re: voltage from egc to neutral
Don
Not if the EGC is landed at the panel and is intact to the point of measurement. I suspect that the EGC is open and you are picking up induced voltage with your digital meter. That is the reason I want you to check from the hot to the EGC using a solenoid voltage tester.
Don
Re: voltage from egc to neutral
I have been using a digital meter. I will check it with the wiggy tomorrow. I told the store manager I was about out of ideas and he might want to get the contractor who wired the store to check it. He said he was not very impressed with the contractor. I am not either after some of the things I have seen. I feel like this problem may be due to faulty work on their part but I just have to find where the problem is. Thanks for the advice.
I have been using a digital meter. I will check it with the wiggy tomorrow. I told the store manager I was about out of ideas and he might want to get the contractor who wired the store to check it. He said he was not very impressed with the contractor. I am not either after some of the things I have seen. I feel like this problem may be due to faulty work on their part but I just have to find where the problem is. Thanks for the advice.
Re: voltage from egc to neutral
Don, I checked with the "wiggy" and L-N is 120,L-EGC is 120,N-EGC is 0. With the digital L-N is 113.5,L-EGC is 116.1,N-EGC is 2.6. In the panel I read 120 L-N,120 L-EGC,0 N-EGC. Upc room is 200 feet from panel,#12 THHN and 8 amp load. Leaving panel first 2 JB's conductor is straight thru with no slack. JB on wall outside UPC room it is wire-nutted and voltage is same there as inside room and in JB just above UPC rack. Seems like problem is on neutral but all connections seem good and I rechecked in the panel. Could they have kinked the neutral when pulling and it compromised the integrity of the wire to cause this. Just grasping at straws. This store runs 24-7 so I cannot kill it out. Also it seems to be constant now whereas it came and went before. I still get some reading on other recepts. but not like on this circuit. By the way the panel is fed from a UPS so problem is in the circuit itself.
Don, I checked with the "wiggy" and L-N is 120,L-EGC is 120,N-EGC is 0. With the digital L-N is 113.5,L-EGC is 116.1,N-EGC is 2.6. In the panel I read 120 L-N,120 L-EGC,0 N-EGC. Upc room is 200 feet from panel,#12 THHN and 8 amp load. Leaving panel first 2 JB's conductor is straight thru with no slack. JB on wall outside UPC room it is wire-nutted and voltage is same there as inside room and in JB just above UPC rack. Seems like problem is on neutral but all connections seem good and I rechecked in the panel. Could they have kinked the neutral when pulling and it compromised the integrity of the wire to cause this. Just grasping at straws. This store runs 24-7 so I cannot kill it out. Also it seems to be constant now whereas it came and went before. I still get some reading on other recepts. but not like on this circuit. By the way the panel is fed from a UPS so problem is in the circuit itself.
- Location
- Illinois
- Occupation
- retired electrician
Re: voltage from egc to neutral
Those numbers look ok. The 2.6 volts between the EGC and the neutral conductor at the load end is really the voltage drop on the neutral. The only way to get rid of it is to increase the circuit conductor size or decrease the load.
Don
Those numbers look ok. The 2.6 volts between the EGC and the neutral conductor at the load end is really the voltage drop on the neutral. The only way to get rid of it is to increase the circuit conductor size or decrease the load.
Don
cripple
Senior Member
- Location
- Santa Fe, New Mexico
The voltage that between the N & EG is the voltage drop due to the current flowing on the neutral conductor as Don stated. There are three solutions,
1. Don stated increase the circuit conductor
2. Shorten the length of the circuit conductor.
3. Place an isolation transformer on the circuit in the UPC room.
By placing the isolation transformer and grounding the output the voltage N to EG will 0, this should correct the problem.
1. Don stated increase the circuit conductor
2. Shorten the length of the circuit conductor.
3. Place an isolation transformer on the circuit in the UPC room.
By placing the isolation transformer and grounding the output the voltage N to EG will 0, this should correct the problem.
- Status