Pvc "hot box" bender is tripping gfci receptacles

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crtemp

crtemp

Senior Member
Location
Wa state
I have a Gardner bender pvc bender. It has a 120 volt heating element that trips a gfci receptacle but only after about 5 minutes of being turned on. I have completely rewired the cord to new and have even gone as far as disconnecting the ground wire just to see if that would help but it makes no difference. Any ideas of what's going on? It's really frustrating because the only available power on construction sites are gfci receptacles.
The breaker never trips only the outlet. Do gfi plugs trip from over current?
 
crtemp said:
I have a Gardner bender pvc bender. It has a 120 volt heating element that trips a gfci receptacle but only after about 5 minutes of being turned on. I have completely rewired the cord to new and have even gone as far as disconnecting the ground wire just to see if that would help but it makes no difference. Any ideas of what's going on? It's really frustrating because the only available power on construction sites are gfci receptacles.
Click to expand...
Most likely is an insulation breakdown inside the heater element as it gets hot. The result is leakage current to ground, but not nearly enough to trip a simple OCPD.
For disconnecting the EGC wire to the bender to work as a test you would have to insure that there is no other connection from the bender case (metal?) to earth ground. Simply sitting on a concrete floor could conceivably carry enough current to trip a GFCI.
 
GoldDigger said:
Most likely is an insulation breakdown inside the heater element as it gets hot. The result is leakage current to ground, but not nearly enough to trip a simple OCPD.
For disconnecting the EGC wire to the bender to work as a test you would have to insure that there is no other connection from the bender case (metal?) to earth ground. Simply sitting on a concrete floor could conceivably carry enough current to trip a GFCI.
Click to expand...

maybe try rubber feet?
 
Just tested it in my garage by running it on a GFCI circuit and placing the hot box on a piece of wood. After 15 minutes the GFCI is still holding.
 
crtemp said:
No. I could hook it back on and try again though.
Click to expand...
Rig it up so you can measure open circuit voltage on that EGC after a warm up period. Then close it and see if it gives you instant trip.

Using on non GFCI protected outlet likely will allow the point of the fault to continue to get worse and will eventually result in more catastrophic failure.
 
kwired said:
Rig it up so you can measure open circuit voltage on that EGC after a warm up period. Then close it and see if it gives you instant trip.

Using on non GFCI protected outlet likely will allow the point of the fault to continue to get worse and will eventually result in more catastrophic failure.
Click to expand...
Hooked it back up and it tripped after 6 minutes. I'll try and find my meter to test it.
 
GoldDigger said:
Most likely is an insulation breakdown inside the heater element as it gets hot. The result is leakage current to ground, but not nearly enough to trip a simple OCPD.
Click to expand...

I have had this same problem with other types of heating elements. When they heat up you can actually measure the leakage (low resistance) from hot to frame and watch it go to normal as the heaters cool.

I would contact the manufacturer about this problem. Heating elements are cheaper than a new hot box and they may even furnish them.
 
Sounds like the heating element is expanding durring heat up and contacting the case.
Same thing happens to clothes dryers and the like that use heating elements suspended by porcelain cleats.

Can you physically get to and see the elements?
 
crtemp said:
I have a Gardner bender pvc bender. It has a 120 volt heating element that trips a gfci receptacle but only after about 5 minutes of being turned on. I have completely rewired the cord to new and have even gone as far as disconnecting the ground wire just to see if that would help but it makes no difference. Any ideas of what's going on? It's really frustrating because the only available power on construction sites are gfci receptacles.
The breaker never trips only the outlet. Do gfi plugs trip from over current?
Click to expand...

if it gets to the point that you need to replace it, i went with this.....

http://www.hotbend.com

https://www.youtube.com/watch?v=zJIhOcowwkg

they run about $850. once you get past the sticker shock,
the think pays for itself pretty quickly. it's insanely fast.
when you light it off, the woosh sounds like a big block
with the secondaries open.

now, i've got one sitting there, with minimal usage. as in
it's damn near brand new. it'd go to a good home for half
price. send me a pm if interested. it's unlikely i'll ever need
it again.

btw, it'll heat up 4" schedule 80 pretty quick. it slows down
on 6" pvc a bit.
 
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