No power stumper

junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
So, widow lady friend at church asked an engineer friend to check it out, he could find nothing, so asked if I could check why her upstairs bath lost power.

NO tripped breakers. So, we spent 3 hours trying to find open connections.

All voltages and connections in panel check out good, tightened all just to be sure.

No GFCI trips. Only GFCI single ended in bathroom.

Opened and checked 8 outlet and light switch boxes, nothing loose. All show no voltage black to white NOR black to ground.

What is strange is that there is no 120 from black to white OR to ground, --- also ground to white shows open circuit.

So, what could cause both open white and black wire. Ground wires all good, test to known good ground checked with a long test lead, ground wires OK.

Her yard is torn up, known to be by local pack of raccoons..... hmm, wonder if raccoons got in somewhere and ate thru a cable without tripping the breaker.

Any other possibilities other than 2 wire nuts or other connections coming loose at same time?

PS: I'd left my RF circuit tracer in the other truck, will need to try that to find break.
 
Plug an extension cord into a working, known-properly-wired, non-GFCI-protected receptacle, and carry the female end with you. Use a solenoid tester to test for voltage between the cord's hot slot and the bad circuit's neutral, and between the cord's neutral slot and the circuit's hot.

Let us know the results. As mentioned above, only another GFCI would normally be the only thing that opens both circuit conductors. When you find it, rewire the line in and line out wires together.
 
I have found buried GFCI receptacle is with the help of the ideal circuit tracer, on a few occasions. Found where the signal was lost in the wall, went to an adjacent room, started moving shelving, boxes, etc, and found a hidden GFCI receptacle.

I also had one a couple weeks ago. Bathroom was dead on a house the HO was remodeling. Not a circuit we had touched. Breaker was in, no power to the bath. Went up in the attic and stated tracing wiring. Found the feed, closest receptacle was live. Using the NC tracer I noticed it “fading”.

I couldnt figure out why when I cut the power in the circuit, and tied H-N, H-G, or N-G, I wasn’t getting continuity, but I knew from visual inspection it was the right circuit.


I cut the romex in the attic, and before the “fade“, everything was fine. I pulled the section of romex out of the wall and fed a new piece and installed a j-box. When I pulled the old piece out, BOTH hot and ground were broken completely through. Only neutral was still intact. Very rare situation, but weird stuff does happen. 👍
 
junkhound said:
So, widow lady friend at church asked an engineer friend to check it out, he could find nothing, so asked if I could check why her upstairs bath lost power.

NO tripped breakers. So, we spent 3 hours trying to find open connections.

All voltages and connections in panel check out good, tightened all just to be sure.

No GFCI trips. Only GFCI single ended in bathroom.

Opened and checked 8 outlet and light switch boxes, nothing loose. All show no voltage black to white NOR black to ground.

What is strange is that there is no 120 from black to white OR to ground, --- also ground to white shows open circuit.

So, what could cause both open white and black wire. Ground wires all good, test to known good ground checked with a long test lead, ground wires OK.

Her yard is torn up, known to be by local pack of raccoons..... hmm, wonder if raccoons got in somewhere and ate thru a cable without tripping the breaker.

Any other possibilities other than 2 wire nuts or other connections coming loose at same time?

PS: I'd left my RF circuit tracer in the other truck, will need to try that to find break.
Click to expand...
As Curt and Larry and James said, look for another gfi, I went to an electrical engineers house once, the master bath didn’t have power, he thought the gfi was bad, and he changed it, still no power. So when I got there, I asked if there was another bathroom, he said yes, a guest bath they never used at the other end of the house. Went over there, pressed the reset button, magically the master bath had power now!
 
Thanks for continuing to look for another GFCI reminder guys. Hidden GFCI may be the answer.

The first friend is an ME vs. EE; even so, a tripped GFCI scenario was the first thing he looked for on first visit, and did not see any GFCI except the single ended one in the bath, so I did not look any further myself yesterday.

Reviewing the searches I recall seeing an outlet with a six outlet extender at one outlet, but there was power there.
I have suggested to the HO that she pull that extender to see if there is a GFCI it is plugged into! If it was wired in backwards, it would explain all. Have not gotten word back yet. HO has lived in the house 15 years with no problems and does not recall seeing any GFCI except the single ended one in the upstairs bath. The ME did note that the downstair bath did not have a GFCI and was going to replace the regular duplex there with a GFCI for the HO, but ran out of time yesterday. That outlet is dead also so suspect it is downstream of the backwards wired GFCI behind the expender.

I forgot to mention in first post that I did look in the attic and no sign of raccoons there having left droppings or any damage.

Next time I'm over there (HO gone for Christmas to relatives now) will take along wire tracer and long extension cords to verify what runs where from the dead bathroom.

PS: Had the exact same scenario as Hillbilly at son's house 15 years ago, tripped GFCI at other end of the house.
 
junkhound said:
If it (gfci )was wired in backwards, it would explain all
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I was going to include this earlier.
Newer gfcis won't work at all if they are wired backwards but older ones would power through.

Also, I've seen a few houses wired in the '80s and '90s where the gfci home run went to a weatherproof receptacle. Not often, as it was unconventional to do so, but I have seen it. Then it looks like nothing in the house is gfci protected because nobody can find a button
 
James L said:
I was going to include this earlier.
Newer gfcis won't work at all if they are wired backwards but older ones would power through.

Also, I've seen a few houses wired in the '80s and '90s where the gfci home run went to a weatherproof receptacle. Not often, as it was unconventional to do so, but I have seen it. Then it looks like nothing in the house is gfci protected because nobody can find a button
Click to expand...
Yeah, I’ve seen them run through the garage receptacles as well as the outside receptacles just to save a gfi receptacle!
 
James L said:
Newer gfcis won't work at all if they are wired backwards but older ones would power through.
Click to expand...
They may work until they actually trip. Then they won't reset if wired backwards. I primarily use Legrand devices and that seems to be the case with their GFCI's. New ones are shipped tripped so won't reset when first powered on, but if you had one set, reversed wiring for whatever reason while it is "set" it continues to pass power until it is tripped again from my observations.
 
kwired said:
They may work until they actually trip. Then they won't reset if wired backwards. I primarily use Legrand devices and that seems to be the case with their GFCI's. New ones are shipped tripped so won't reset when first powered on, but if you had one set, reversed wiring for whatever reason while it is "set" it continues to pass power until it is tripped again from my observations.
Click to expand...
It shouldn't if it meets the current UL requirements. They are not supposed to pass power if line/load is reversed.
 
hillbilly1 said:
Yeah, I’ve seen them run through the garage receptacles as well as the outside receptacles just to save a gfi receptacle!
Click to expand...
The way I learned starting back in 1992 was that the closest receptacle inside the structure got the GFCI device and everything else was on the load side.

If it was in the basement, all good. Garage, all good. Half bath, hall bath... It didn't matter as long as it wasn't outside. We used to put all the outdoor receptacles on it, but boss didn't want to use GFCI covers.

I don't know how many call backs. We had, just showing people where they could find the reset button.
 
curt swartz said:
It shouldn't if it meets the current UL requirements. They are not supposed to pass power if line/load is reversed.
Click to expand...
James L said:
Old ones used to.
Haven't seen newer ones (post-2005-ish) do that
Click to expand...
I can experiment with one and let you know, but pretty certain the current ones Legrand has do what I mentioned earlier.

They need power on line terminals before they will reset. If not powered the test button may appear to mechanically reset, but will pop back out once power is applied. I'm assuming this is the condition they are in when you get a new one as they always pop out to trip position first time you power them up, whether wired correctly or not. But if not wired correctly (line vs load) they won't stay reset when you try to reset them. Contacts do remain closed during a power loss and remain closed when power is restored. How is it going to tell whether line/load is reversed if contacts never open during power loss? Now the chances of someone reversing line/load isn't going to be something that will normally happen, but not impossible either.

IIRC there is isolation when tripped that never used to be on older versions so that the load side terminals are also disconnected from the receptacle slots when it trips. As in likely has both line side and load side set of contacts that operate when tripping. I might get a chance to check this out soon and if so will let you know what I find.
 
I had one that an electrical engineer laid out the circuits for a large customer of his, the maids tripped the gfi, nobody could find where it was at. Luckily they had a suspended ceiling in the basement, and I was able to track it down. Turned out, it was under a workbench in the basement behind some tools.
 
kwired said:
I can experiment with one and let you know, but pretty certain the current ones Legrand has do what I mentioned earlier.

They need power on line terminals before they will reset. If not powered the test button may appear to mechanically reset, but will pop back out once power is applied. I'm assuming this is the condition they are in when you get a new one as they always pop out to trip position first time you power them up, whether wired correctly or not. But if not wired correctly (line vs load) they won't stay reset when you try to reset them. Contacts do remain closed during a power loss and remain closed when power is restored. How is it going to tell whether line/load is reversed if contacts never open during power loss? Now the chances of someone reversing line/load isn't going to be something that will normally happen, but not impossible either.

IIRC there is isolation when tripped that never used to be on older versions so that the load side terminals are also disconnected from the receptacle slots when it trips. As in likely has both line side and load side set of contacts that operate when tripping. I might get a chance to check this out soon and if so will let you know what I find.
Click to expand...
I did some experimenting with a new Legrand GFCI receptacle. Here is my observations.

Brand new never used yet, connected supply to the line terminals - unit tripped immediately. Reset and functioned as is supposed to for normal and during ground fault conditions.

Voltage applied to load terminals with unit in tripped state before applying voltage - no voltage at line terminals or receptacle face. Reset button may or may not hold in when pressed. When it does hold in however it did not pass voltage to face or line terminals, it did trip immediately when voltage was properly applied to line terminals again similar to what it does when new and never used yet. Trip indicator never lit up at any time while voltage was applied to load terminals.

Unit in "set condition" then voltage applied to load terminals- unit passed voltage to both line terminals and receptacle face. Once tripped however would not reset again and would not pass voltage to face or line terminals either.

Applied voltage to line hot terminal and load neutral terminal and it tripped immediately would not reset, no voltage to receptacle face.

An after thought, I maybe should have seen what happens if voltage were back fed into face of the receptacle. My guess is if it were in a reset state it would feed voltage to both line and load terminals but likely wouldn't feed through to either once it is in a tripped condition, as well as it likely would not reset in this condition either, most likely would feed voltage to the other receptacle of a duplex unit though.
 
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