I'm pulling 120V control wiring in an existing conduit at a local winery for valving to modulate glycol for temp. control on fermentation tanks and noticed the EGC has almost completely melted off. The conduit and junction boxes are all PVC. The circuits are all fed from a nearby PLC panel- 10 amp IEC breakers. When I pulled the cover off the first box the ground wires were melted into the cover and the insulation was gone. Any ideas on what could have happened? Nobody on site remembers ever having a problem with any associated equipment. If a ground fault large enough to completely melt the insulation off a 14ga thhn conductor, why didn't it trip any OCPD's? Where is the evidence of such a fault? (other than the wire) It is a temp controlled damp environment and I noticed cold air is traveling from the NM flex connecting the valve into the junction box where splicing is made. (typical for two valves each at 12 tanks) Two of the tanks are near large roll up doors, which are opened for maintenance purposes. The only thing I can come up with as a cause is excessive condensation in the junction boxes, perhaps in summer months when the doors are open. As for now I'm planning on duct sealing the conduits and using wet location wire nuts. Any ideas???? Thanks for your input.
troubleshooting a melted EGC
- Thread starter danger30
- Start date
- Status
- Location
- Massachusetts
Just a thought, has anyone been welding?
I have repaired melted EGCs a couple of time from welders placing the work clamp on the nearest grounded metal and then welding across the room with the only path being 12 AWG EGCs.
I have repaired melted EGCs a couple of time from welders placing the work clamp on the nearest grounded metal and then welding across the room with the only path being 12 AWG EGCs.
- Location
- Massachusetts
I think if the place is built like you describe the EGC would be fine. So I have no idea what may have happened.:-?
ericsherman37
Senior Member
- Location
- Oregon Coast
In our neck of the woods, we call things like that "magic."
Did any of the other conductors show any heat damage like that? Or just the EGCs?
quogueelectric
Senior Member
- Location
- new york
Clamp the egcs and find the ssource by throwing breakers one by one.
ericsherman37
Senior Member
- Location
- Oregon Coast
Maybe someone forgot to pull a neutral to some piece of equipment and just hooked up the EGC to the neutral terminal. :-?:-?
(grasping at straws)
(grasping at straws)
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
That sounds like a 'yes' to Bob's question, unless you're sure that no welding was done since the wiring was installed.
Spent the day replacing the ground wire with new. (wouldn't let me replace everything)All devices (valves) checked out OK with no signs of damage or evidence of a fault. As unlikely as it seems to me, I'm going to have to blame the damage on welder current. Could enough current travel through a 14ga control wire? Why wouldn't the majority flow through the steel?
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
Another thought on this subject.
If there is a high resistance ground fault occuring, this could have also caused the melting conductor without opening an overcurrent device.
Once you make up the new conductors, pay attention to what occurs. You may experience another ground fault condition, unless of course the original fault burned clear, which is possible if the condensation is the culprit.
Also, have there been any utility incidents or lightning, recently or even maybe last year?
If there is a high resistance ground fault occuring, this could have also caused the melting conductor without opening an overcurrent device.
Once you make up the new conductors, pay attention to what occurs. You may experience another ground fault condition, unless of course the original fault burned clear, which is possible if the condensation is the culprit.
Also, have there been any utility incidents or lightning, recently or even maybe last year?
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
Much less. Stainless steel (304 or 316) has approximately 2.5% the conductivity of hard annealed copper. The welder might very well be the culprit.
kwired
Electron manager
- Location
- NE Nebraska
stainless may have less conductivity but that would be a 14 AWG stainless wire as compared to 14 AWG copper. Most likely the cross sectional area of the possible current path through the stainless steel is much larger than the CSA of the 14 AWG copper. The OP indicated that almost everything around is metallic and has many mechanically bonded connections
- Status