Hot pipes at a local bar

[JOHNEO99]

I went to a friends bar to look at one of his two panels a month ago. He has a 2 gang meter socket outside that has a 120/240V 200 amp riser. From the can there are two pipes going down into the basement. One pipe is a one inch feed to a 100 amp panel and the other pipe is a one and one half inch pipe going to a 125 amp panel. The first time I looked at this job I noticed a breaker was tripped so I folded it out and noticed that the breaker had damaged the bus bar so I told my buddy he should change out this panel. I moved the breaker to a different position and said I would do it for him for time and material since he is a good friend and I have already done some things over there pro bono. I also told him I would only charge him 20$/hr. which is less than 50% of what I bid things out at. He scoffed and said "I dunno man lets just see how it goes". I told him its gonna go the same way and I also have to make sure the circuits are phased properly and everything is grounded and bonded correctly or the new panel may do the same thing. My buddy is notoriously cheap and said he will let me know when I can do the work. I told him it would only cost him 500-600$ because he is a friend.

Today I get a text from him saying that the main pipe going to the can is too hot to keep his hand on it and something sounds like its frying bacon. I told him I would come out right away to look at it again and do the work if he let me. So I go out to look at it again so as to make sure I have all the material i need since its been a while since I looked at it. I immediately felt the raceway going out to the can and it was pretty damn hot. I looked for loose wires in the main breaker then I went outside to look at the can to see if anything was loose. All the wires were tight and looked to be the correct size. I also noticed the wires themselves were not hot just the raceway.

I really didn't have time to check all the wiring and bonding/grounding but besides overloading (which I didn't see) I am thinking something is going on with the neutrals. It just seems odd to me that this raceway could get so darn hot. I haven't seen anything quite like this. I have seen hot wires but never a hot pipe like this. I am wondering if the raceway has become the neutral and how it could if the neutral is connected right between the can and the panel. I'm a little perplexed but I am sure we will right this.

Has anyone ever experienced something like this and if so what was it?

 

[hillbilly1]

I've seen this before, the conduit was being used as the equipment ground, there was a fault in the enclosure it was attached to, but due to the locknuts not being tight there was a high resistance path that the current was taking, not enough to trip the breaker though. The current at the locknut was heating the pipe.

 

[JOHNEO99]

That makes sense. What kind of enclosure was it?

 

[hillbilly1]

That makes sense. What kind of enclosure was it?

It was between a 100 amp 277/480 volt service disconnect and the enclosure containing the panel and contactors for parking lot lighting, one of the feeds to the poles was faulting underground. I noticed the locknut had burn marks on it, and the can. The conduit (yes, Bob it was conduit, RMC :lol was hot. (I also noticed the sparks flying when I turned the contactors off)

 

[kwired]

Are all conductors of the circuit(s) within the raceway? If not that can cause heating of the raceway.

 

[PURE]

HOT GROUND WIRE

HOT GROUND WIRE

Had similar experience yesterday, 120/240v standard residential service, slab house back to back 200amp panel and meter can.
Ground wire coming out the bottom of the panel going to the ground rod, RED HOT. melted the siding and caused the plywood to catch fire. 20 year old service, aluminum conductors, every connection in the mater and panel very very loose.
even if neutral coming in had a bad connection, house load very small, would not do enough to get ground that hot.
Any chance the utility transformer/conections bad, using ground rod to earth a fault? all utility is underground.

 

[kwired]

Had similar experience yesterday, 120/240v standard residential service, slab house back to back 200amp panel and meter can.
Ground wire coming out the bottom of the panel going to the ground rod, RED HOT. melted the siding and caused the plywood to catch fire. 20 year old service, aluminum conductors, every connection in the mater and panel very very loose.
even if neutral coming in had a bad connection, house load very small, would not do enough to get ground that hot.
Any chance the utility transformer/conections bad, using ground rod to earth a fault? all utility is underground.

Did you by chance measure how much current it was carrying?

Hard to believe a ground rod would have a low enough resistance to earth to allow the kind of current needed to heat it up that much to flow - assuming you have at least 6 AWG to the ground rod, but even a 10 AWG would likely not get that hot.

Maybe if there is POCO primary voltages involved it could happen, there would also be be high voltage gradients around that rod and from all grounded items connected to that service making a very serious shock hazard.

Another possibility - ground rod driven into a buried conductor.

What did you find? This isn't something where you just replace what is obviously bad and hope it doesn't do it again.

 

[ggunn]

Hard to believe a ground rod would have a low enough resistance to earth to allow the kind of current needed to heat it up that much to flow - assuming you have at least 6 AWG to the ground rod, but even a 10 AWG would likely not get that hot.

Couldn't this happen with an open neutral from the service to the main panel? Wouldn't it make the GEC the only available return path for unbalanced load currents?

 

[kwired]

Couldn't this happen with an open neutral from the service to the main panel? Wouldn't it make the GEC the only available return path for unbalanced load currents?

Yes but how much current will it take to make it get red hot??

If you had a ground rod with 10 ohms of resistance and directly connected 120 volt ungrounded conductor to it, only 10 amps will flow. If it has a 6 AWG conductor run to it then it should be able to do that indefinately as far as the conductor goes.

A poor connection at either end of the conductor will only heat a few inches of conductor near the bad connection.

 

[PURE]

DP&L

DP&L

Power company came out to verify it was not the underground, they disconnected at both ends and ran continuity check...
But i never seen them check to the ground rod... just between 3 wires. If ground rod was hitting one leg of underground and feeding from the ground rod back to the neutral bar? yes the service has a #6 bare ground fyi.

 

[kwired]

Power company came out to verify it was not the underground, they disconnected at both ends and ran continuity check...
But i never seen them check to the ground rod... just between 3 wires. If ground rod was hitting one leg of underground and feeding from the ground rod back to the neutral bar? yes the service has a #6 bare ground fyi.

Continuity check is not what is needed, Meg from the potential damaged conductor to earth to find if a ground rod was driven into a conductor.

 

[JOHNEO99]

Well I am going to fix the problem tomorrow. I noticed the only electrode is one piece of galvanized pipe pounded into the ground that has a #4 terminated to it with a J-clamp and this goes to the two gang meter can and serves two separate panels. No bond inside whatsoever besides the hot raceway. The raceway gets hotter when misc. items kick on and off and the load increases on the panel. I had the owner turn off each breaker individually for 20 minutes to see if we could isolate a circuit as being the problem but it didn't seem to matter much unless it was a circuit with a more continuous type load.

 

[Sierrasparky]

I cannot believe you left there with the power on and the pipes hot.
I wou;d never have left with a problem of you described.

 

[JOHNEO99]

It wasn't like that when i was there the pipe was hot but not like that at all. when i went there it was late. I have warned this guy to no end.

 

[kwired]

You said in OP you suspect a neutral problem. This is a possibility. Check current on ungrounded lines and see if neutral conductor is carrying the unbalanced value. If it is low then it is going someplace else, if it is high you are picking up additional current from the other panel or even from someplace outside the facility via grounding electrodes or other metallic paths. Also check for fall of potential between the neutral bar and the neutral conductor very little or no voltage there means that connection is probably good. Also need to check at the meter for same thing.

 

[stickboy1375]

Pretty soon you won't have to worry about fixing it.

 

[Dennis Alwon]

There can be a few things going on including a bad wire in the pipe. Is there a gec run in this metal pipe with no bonding bushing. You may be experience a choke effect on the conduit. Just another possibility.

 

[JOHNEO99]

The only GEC is from the meter can outside to the galvanized pipe outside 10 ft. of #4. The panels are only bonded to the can by pipe with zero bonding bushings so basically two locknuts.I will let you guys know whats up with this tomorrow.

 

[jaylectricity]

Check current on ungrounded lines and see if neutral conductor is carrying the unbalanced value.

I just want to know if I understand this right. So I would take an amp clamp meter and put the clamp around one of the ungrounded conductors and record the result. Then put the clamp around the other conductor and subtract that result from the other. Then put the clamp meter around the grounded conductor and see if it was equal to the difference of the ungroundeds?

 

[wirenut1980]

I just want to know if I understand this right. So I would take an amp clamp meter and put the clamp around one of the ungrounded conductors and record the result. Then put the clamp around the other conductor and subtract that result from the other. Then put the clamp meter around the grounded conductor and see if it was equal to the difference of the ungroundeds?

Yep, you got it. It should be close, maybe not equal.