Equipment Grounding Conductor to Motors

[jim gerlach]

Is it a code requirement that a separate equipment grounding conductor be pulled with motor leads from an MCC to the local disconnect and then to the motor? Cannot the raceway (conduit) still serve as it has in the past?

Thanks

 

[friebel]

Re: Equipment Grounding Conductor to Motors

To: Jim gerlach, Jim, I have answere this question before in a previous post, but I do not mind giving you my opinion.
Yes, you can relay upon the conduit for your grounding conductor for your motor, that goes back to your MCC. We did this for many years at a Dupont plant. We do not do it today. We carry a grounding conductor inside of the conduit, from the motor back to the MCC. The reason that we changed was for Safety. Many times the coupling on the conduit would become corroded and then you have lost your grounding continuity. Or the conduit becomes broken. Again you have lost your ground. Jim,today I would always carry a ground wire in the conduit for Safety.
regards, bob friebel

 

[don_resqcapt19]

Re: Equipment Grounding Conductor to Motors

I agree that the code does not require the EGC in the conduit, but also recommend that it be installed. Note that if you do not install an EGC in the raceway a bonding jumper will be required around any flexible raceway that is used between the conduit and the motor junction box.
Don

 

[tom baker]

Re: Equipment Grounding Conductor to Motors

In most cases the raceway can qualify as an equipment grounding conductor, see 250.118. there are limitations on the use of LTMC and FMC, as to the OCPD size and size of flex.
For a motor circuit the size of the EGC is based on the overload size, for smaller size LTMC its limited to 20A to be approved as a EGC. You are far better off just to required a EGC in every raceway, and not have to determine the raceway size and type for including an EGC in the specs.

Now if these are 277/480 V circuits, then its even more critical that an EGC be included. 277 V circuits have 5 times the heating energy of a 120V on a ground fault. I spec a assured bonding method on one end of every raceway containing a 277 V circuit, regardless of KO type.

 

[jlr134]

Re: Equipment Grounding Conductor to Motors

Tom...this is something thats debated at work all the time.Does the code REQUIRE an EGC in flexible conduit to a motor IF the run complies with the limitations or 250.118 ? Not should we but must we ( and were only speaking of fractional Hp motors...120vac motors by the way.)I keep saying its not required.

 

[don_resqcapt19]

Re: Equipment Grounding Conductor to Motors

jlr134,
In most cases, the FMC to the motor is not securely fastened in place within 12" of the FMC termination. If you do not provide the supports required by 348.30(A) then you must be using Exception #2. If you are using this exception, then 250.118(6)(d) does not permit the FMC to be an EGC.
Don

 

[jlr134]

Re: Equipment Grounding Conductor to Motors

Thanks