Ground Bushing Req?

[Dustin Foelber]

I have a 30 amp 3pole Nema 3 disconnect mounted to my air unit. We have a 3/4 gal. stub that adapts to seal tite to feed the disconnect. My crew installed the seal tite connectors in a concentric knock out on the bottom of the disconnect. The maximum allowed for the concentric is 1". If I am using only up to 3/4 do I need a ground bushing on the seal tite connector?
Thank you for you input
D

 

[raider1]

What is the voltage?

Typically outside of hazardous locations and the line side of the service, grounding bushings are not required.

Take a look at 250.97 for circuits over 250 volts.

Chris

 

[Dustin Foelber]

The Voltage is 480 Volt 3 phase.:-?

 

[augie47]

If the sealtite is listed as suitable for grounding (some types are not..type EF is not, I believe) and it is less than 6 ft then, per 250.118 it is a suitable equipment ground. Most likely your disconnect is listed as an acceptable ground with the eccentric knockouts but you could check your switch manufacturer rep to make sure (as Chris directed, look at 250.97)
Are you relying on the conduit system as the equipment grounding means ?

 

[Dustin Foelber]

We have a 10 AWG Equipment ground in the conduit that is bonded to the disconnect. But the conduit entry is concentric. I was told all concentrics not using the largest conduit entry need ground bushings. Is that false?

 

[augie47]

I hope I say this right. The older I get the more I confuse myself. If I;m incorrect, Chris will fix it
First. Since you pulled an equipment grounding conductor the switch is grounded. The conduit would need to be bonded, of course, but an acceptable termination on either end would provide that.
The exception to 250.97 would address the bonding at the switch end. As you can see it states "where the enclosure is listed...". The manufacturer could confirm that. My experience has been that most are listed.

 

[raider1]

I agree with Gus.

Chris

 

[augie47]

(whew, I passed) unusual lately View attachment 3508

 

[SEO]

Gus you usually get high scores hang in there.:smile:

 

[dcspector]

(whew, I passed) unusual lately View attachment 3508

Gus I am right up there with you. Your posts are usually dead on for an old F**t..:grin:

 

[220/221]

I was told all concentrics not using the largest conduit entry need ground bushings.

Over 250 V to ground.

The Voltage is 480 Volt 3 phase.

Well there you go. Over 250V to ground = bond bushing.

 

[augie47]

I was told all concentrics not using the largest conduit entry need ground bushings. Is that false?

I may be wrong, but I don't think that's a given. Again, look at 250.97 Exception. Box (enclosure) listing is the key.

 

[paul]

Raco's 4-square deep box is listed to use the eccentric knockouts without a bushing.

http://www.hubbellcatalog.com/raco/...oBoxes&P=12842,11447,11448,1077,386,9206,1078

Features RACO's patented TKO 1/2" & 3/4" eccentric knockouts (Per U.L. 514-A, suitable for use without a bonding jumper in circuits above or below 250 volts)
Combination cover screw heads provide for faster mudring/cover installation
Raised ground provision in back of box

 

[dcspector]

Raco's 4-square deep box is listed to use the eccentric knockouts without a bushing.

http://www.hubbellcatalog.com/raco/...oBoxes&P=12842,11447,11448,1077,386,9206,1078

Paul same thing in the UL White Book (QCIT)

 

[paul]

It's something new that I learned today. I will still run my 1/2" lighting runs into the 1/2" KO's just out of habit. :grin: