I have a problem with a high resistance on grounding conductor. the resistance is around 3 ohms. I know it is good enough to pass code but the client wishes it to be more around zero. He uses the equip for high end audio testing. All other recepts in the building are good. But the ones coming off a transformer to a panel upstairs are the ones being affected. Could the transformer be wired wrong( like the secondary Xo being hooked up to the equip ground?) would that cause the problem? I'm not sure how to help him at this point. Any suggestions?
high resistance on grounding conductor on secondary side of transformer
- Thread starter pinkvolt
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Please clarify the question. What conductor has the high resistance (i.e., the phrase "grounding conductor" could have several meanings)? To start with, by what means is the transformer XO attached to planet Earth? Does it have a short conductor to a ground bar within the room, with that bar connected to a ground bar in the main electrical room, and is it the GEC from that bar to the grounding electrode system that has the high resistance?
Welcome to the forum.
Welcome to the forum.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Take a look at the following art 100 definitions and rephrase your question
Equipment grounding conductor
Grounding electrode conductor
Grounding electrode
and in Art 250
System bonding jumper
What do you mean the 3 ohms meets code? What section?
Equipment grounding conductor
Grounding electrode conductor
Grounding electrode
and in Art 250
System bonding jumper
What do you mean the 3 ohms meets code? What section?
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
I still don't understand what you are measuring. Exactly where are you touching the probes, when you measure resistance? Do you, for example, touch one probe to the inside of the receptacle's round hole, and the other probe to the outlet box? Do you have a really long test lead, and is the second probe touching the ground bar in the panel, or perhaps a ground rod outside the building?
brian john
Senior Member
- Location
- Leesburg, VA
1. What is the test equipment?
2. Where are you reading from (As Charlie asked) and too?
3. Has your tester been calibrated lately?
When testing anything and the readings seem out of kilter
Always check the equipment you are testing with.
Alway question the testers methods.
Then trouble shoot the possible issue at hand.
2. Where are you reading from (As Charlie asked) and too?
3. Has your tester been calibrated lately?
When testing anything and the readings seem out of kilter
Always check the equipment you are testing with.
Alway question the testers methods.
Then trouble shoot the possible issue at hand.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Is this ground to neutral?
Maybe its a neutral issue.
If this is for audio you may want to consider isolated ground recpts. Some don't like but can't hurt and can help with audio
cripple
Senior Member
- Location
- Santa Fe, New Mexico
high resistance on grounding conductor on secondary side of transformer
You stated that the receptacles being fed from a panel which fed form a transformer are the ones with the three ohms to ground.
Is this all receptacles fed form this panel?
If so you may want to check the transformer connection, it sounds like the transformer if not grounded or the system bounding jumper is not installed or not terminated properly.
I feel the best way to verify the integrity of the connection is to check it under load. Load the panel and check and record the voltage reading, phase to phase, phase to neutral and neutral to ground. When you could place a load on the circuit (receptacle), and check the voltage between neutral and the equipment grounding pin on the receptacle and compare the voltage reading with the panel and the good receptacles.
This could should gave you a good start to pin point the problem.
You stated that the receptacles being fed from a panel which fed form a transformer are the ones with the three ohms to ground.
Is this all receptacles fed form this panel?
If so you may want to check the transformer connection, it sounds like the transformer if not grounded or the system bounding jumper is not installed or not terminated properly.
I feel the best way to verify the integrity of the connection is to check it under load. Load the panel and check and record the voltage reading, phase to phase, phase to neutral and neutral to ground. When you could place a load on the circuit (receptacle), and check the voltage between neutral and the equipment grounding pin on the receptacle and compare the voltage reading with the panel and the good receptacles.
This could should gave you a good start to pin point the problem.
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