Using a conveyor frame is a ground fault path

[reyamkram]

I ran into this, for pneumatic valve control box there was no equipment ground conductor and they told me they're using the conveyor frame as the ground fault path I don't believe that is proper or right and it can't have a high impedance and won't open the over current device I try to look this up in the NEC couldn't find anything, I look in 250.118, couldn't find anything that says I cannot use a conveyor frame as ground fault path, no to conveyor frame is not bonded all the way back to the source actually it's not bonded at all any suggestions or help that I can find to present this to the bosses and make it right,

Thank you for any and I'll help

 

[ptonsparky]

Is there an equipment ground to any of the items mounted to the frame?

 

[Master Nater]

when you say that there is no EGC, you mean that there's no metal conduit running to it?

then again, your own cited code goes into things just a bit.

250.118(B) - NOT PERMITTED
1 - GEC
2 - structural metal frame of a building or structure.

i would say that 'structure' includes conveyor structures. even if it is properly grounded/bonded.

 

[infinity]

What wiring method is used to carry the branch circuit to the equipment?

 

[kwired]

Metal raceways qualify as equipment grounding conductors, with some limitations particularly on length of flexible metal conduit.

The frame will very likely carry current during a fault, but NEC doesn't allow it to be considered an EGC path.

In general the EGC must be run with the wiring method or the wiring method itself must qualify as an EGC.

 

[infinity]

What about 250.136 if the EGC is brought to and connected to the frame with the branch circuit?

250.136 Equipment Secured to Grounded Metal Supports.
Electrical equipment secured to and in electrical contact with a metal rack or structure provided for its support shall be permitted to be considered as being connected to an equipment grounding conductor if the metal rack or structure is connected to an equipment grounding conductor by one of the means indicated in 250.134.

 

[don_resqcapt19]

I look in 250.118, couldn't find anything that says I cannot use a conveyor frame as ground fault path,

You can only use the things listed in 250.118 as an Equipment Grounding Conductor. If it is not on the list it is not an EGC.

 

[infinity]

You can only use the things listed in 250.118 as an Equipment Grounding Conductor. If it is not on the list it is not an EGC.

I was referring to using the rack once it's connecting the EGC.

 

[don_resqcapt19]

I was referring to using the rack once it's connecting the EGC.

I have never understood how that could be used without a violation of 300.3(B).

 

[infinity]

I have never understood how that could be used without a violation of 300.3(B).

I'm remembering a graphic in either the NECH or maybe one of Mike's books where they showed a piece of strut being used as the EGC. I'm with you, why is this even in the NEC.

 

[TwoBlocked]

Then there is from NEC 2020 (emphasis mine)

250.96 Bonding Other Enclosures

(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings and other metal non-current-carrying parts that are to serve as equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded ...

For instance, we often fabricate supports for enclosures from strut, making sure that all mechanical connections are metal to metal. In each enclosure, the ground from any power circuits is bonded to the enclosure, which is bonded to the fabricated "structure" through it's mounts. I see no need to run separate EGC between every piece of the structure and to the EGCs in each enclosure.

I see this as no different to the original post, using the framing of a conveyor as an EGC.

 

[Master Nater]

250.188(A) Types of EGCs - Permitted - Each equipment grounding condcutor RUN WITH or ENCLOSING THE CIRCUIT CONDUCTOR shall be one or more or a combination of the following:

the EGC must be "run with" or "enclosing" (as a raceway) with the circuit conductors.

 

[don_resqcapt19]

I see no need to run separate EGC between every piece of the structure and to the EGCs in each enclosure.

In my opinion, 300.3(B) requires an EGC to be run with each set of power conductors.

 

[TwoBlocked]

In my opinion, 300.3(B) requires an EGC to be run with each set of power conductors.

Hope I can say this how I mean to.

Yes, an EGC must be run with power conductors. Additionally, all metal parts need to be bonded to ground. This bonding is done with EGCs, which can be the metal parts themselves.