Earth fault
- Thread starter sivaji
- Start date
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ramsy
NoFixNoPay Electric
- Location
- LA basin, CA
- Occupation
- Service Electrician 2020 NEC
Re: Earth fault
Without knowing much about UPS stuff, common sense makes me think branch circuit ground faults trip GFCI's & breakers, and would leave that UPS running on batteries all the time.
But, a slow leak through load side equipment may not trip anything. Maybe a controlled shut down of load-side equipment, at some point would make it go away?
The UPS manual may suggest other causes for that indicator, or suggest reseting or swapping the UPS, after a controlled shutdown of attached loads.
If the branch circuit is faulting to earth/ground, without tripping breakers, then equipment cases will also stay energized.
If equipment grounding prongs and cases are energized with the branch-circuit phase then placing a volt meter neutral to ground may show line voltage. (previous H-G idea deleted)
But, doing that with a Wiggy's (solenoid tester) could trip GFCI's and crash the connected data processing loads. Common inductive multimeters don't usually draw enough current to trip GFCI's.
[ December 25, 2005, 08:30 AM: Message edited by: ramsy ]
Without knowing much about UPS stuff, common sense makes me think branch circuit ground faults trip GFCI's & breakers, and would leave that UPS running on batteries all the time.
But, a slow leak through load side equipment may not trip anything. Maybe a controlled shut down of load-side equipment, at some point would make it go away?
The UPS manual may suggest other causes for that indicator, or suggest reseting or swapping the UPS, after a controlled shutdown of attached loads.
If the branch circuit is faulting to earth/ground, without tripping breakers, then equipment cases will also stay energized.
If equipment grounding prongs and cases are energized with the branch-circuit phase then placing a volt meter neutral to ground may show line voltage. (previous H-G idea deleted)
But, doing that with a Wiggy's (solenoid tester) could trip GFCI's and crash the connected data processing loads. Common inductive multimeters don't usually draw enough current to trip GFCI's.
[ December 25, 2005, 08:30 AM: Message edited by: ramsy ]
physis
Senior Member
Re: Earth fault
I'm wondering why, if there's a ground fault, a circuit breaker isn't tripping too. It makes me think it's either not much current or the fault indication is lying.
Have you verified that there's current on the EGC at the UPS?
You can find a ground fault by putting an amp clamp on the EGC.
A tic tracer might be able to pick up a fault on a cabinet but I don't know.
I'm wondering why, if there's a ground fault, a circuit breaker isn't tripping too. It makes me think it's either not much current or the fault indication is lying.
Have you verified that there's current on the EGC at the UPS?
You can find a ground fault by putting an amp clamp on the EGC.
A tic tracer might be able to pick up a fault on a cabinet but I don't know.
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