Electrician asking guidance. Customer complaining of shock when touching metal sink and stove.
Sink to stove voltage reads 3 to 5 volts. Same reading sink to grounding terminal on nearby receptacle.
Thinking is that the voltage is originating from a bad water heater element.
Trouble shooting scheduled to continue tomorrow.
(Commercial installation. Water heater supply source unknown, no disconnect)
Input ?
Solution: Tell customer not to touch sink and stove simultaneously.
Kidding aside, there are several possibles here to me:
1) Does the sink have a garbage disposal? If not...
2) Does the sink have PEX mains AND PVC drains? If yes, then I would not suspect the sink as the source.
If yes to #1, does shutting off the breaker for the garbage disposal eliminate the 3-5V? If yes, then the garbage disposal is the likely fault
If no to #2, there is likely a bonding issue with the water supply. There could be something really odd, like a piece of damaged NM touching the drain line, tho I think that would cause more than one person to report a shock problem.
3) Does shutting off the breaker to the stove eliminate the voltage to the sink? If yes, there is probably a fault in the stove. If not, does testing from the stove to another grounding conductor give the same 3-5V reading? If yes, I'm guessing a ground loop.
You said this is a commercial space - what kind? If it's like a restaurant, then only one tenant or person is likely to complain about shock. If it's a multi-tenant building and no one else is complaining, well, they all have shared water supply and drains but only THIS person is reporting shock to a stove - I'm guessing the stove is the culprit.
eta: I dont suppose installing a bonding jumper from stove to sink is NEC compliant here?
