Kiln wiring and bonding the EGC to a switch.

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nhfire77

Senior Member
Location
NH
Wiring a 240 VAC 1PH 4 wire Kiln:

(needs the neutral for its computer controller):


Regarding the EGC feeding kiln, would you bond it to the disconnect switch?

Or

Do you run a separate conductor, essentially a parallel grounding path.


The neutral is just there for the CPU, the EGC is the reference for the the heating elements, would this lead to objectionable current?

There is a piece of FMC involved here so the raceway won't be the EGC (kiln is drawing 60 Amps).

I ask all this because, if I add the 5th conductor, I am going up a size on my raceway, its doable, just a PITA.
 

nhfire77

Senior Member
Location
NH
Bond it, Why would you want 2 EGC's? 4 Wires is all you need.

~Matt

I had a "kiln guy" wonder about this. I thought bonding it was fine, asked me to check on this, because he is responsible for the Kiln and I have to provide the raceway. I already put it what was needed, but, if I have to change it, I want a reason.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Regarding the EGC feeding kiln, would you bond it to the disconnect switch?

Or

Do you run a separate conductor, essentially a parallel grounding path.
One GEC for all external parts of both the circuit equipment and the appliance. Of course, the circuit neutral must not be bonded.

The neutral is just there for the CPU, the EGC is the reference for the the heating elements, would this lead to objectionable current?
If you mean there's an electrical connection to the heating elements, then yes, this is wrong. The neutral should be the reference, if I'm understanding your meaning.


Recap: One grounded circuit conductor, and one equipment grounding conductor. The latter should have absolutely no connection to any energized part, regardless of what voltage it may or may not have.

Four conductors, not five.
 
You have to bond it to the Disconnect, all metal parts must be kept at the same potential, if you run a parallel path you may run into a problem of the ocpd not tripping during a ground fault condition, the current will split along the different pathways.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I'm a little slow :) so I don't understand the question, or rather I see two questions.
As has been stated, all metallic components should be bonded, so, yes you disconnect should be bonded to the incoming equipment grounding conductor.
In addition, since it is a 60 amp circuit FMC can not be the equipment ground to the Kiln and a separate grounding conductor needs to be installed.
The groundED conductor can not be used as the equipment grounding means.
 

nhfire77

Senior Member
Location
NH
Never mind, thanks anyway. I got sucked into some bad info, the kiln guy had me all confused.

I need sleep more and type dumb questions less ;)

The EGC is bonded to the switch/kiln/raceway. There is no groundED conductor involved, except at the panel.

Thanks anyway.
 

gndrod

Senior Member
Location
Ca and Wa
Wiring a 240 VAC 1PH 4 wire Kiln:

(needs the neutral for its computer controller):


Regarding the EGC feeding kiln, would you bond it to the disconnect switch?


The neutral is just there for the CPU, the EGC is the reference for the the heating elements, would this lead to objectionable current?

There is a piece of FMC involved here so the raceway won't be the EGC (kiln is drawing 60 Amps).

I ask all this because, if I add the 5th conductor, I am going up a size on my raceway, its doable, just a PITA.

If the FMC is the raceway, and flexibility is not required after installation, then the FMC is permitted to be used as the EGC. [348.60] rbj
 
Last edited:

gndrod

Senior Member
Location
Ca and Wa
Correction 250.118(5)

Correction 250.118(5)

If the FMC is the raceway, and flexibility is not required after installation, then the FMC is permitted to be used as the EGC. [348.60] rbj

Gus is correct. The 60Amp disqualifies the FMC as an EGC regardless of inflexibility. My bad. rbj
 
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