Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
When using a MIGB are they usually only installed at pull boxes or everywhere along the run where the conduit terminates? Equipement etc.? Thanks
Grounding Bushing
- Thread starter Alwayslearningelec
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What is the application that requires them? Unless you're using boxes or enclosures where there are concentric or eccentric KOs and over 250 volts to ground they're not required. For decades I laughed at guys who insisted that they're required for transformers.
Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
No specific situation right now. Just a general thought and question. So if the engineer specifies them but the application you explain does not apply they are not required?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
They are rarely ever required. If the voltage is 208Y/120 or 120/240 they are not required even for concentric and eccentric KO's. For 480Y/277 they're required when there are concentric or eccentric KO's in certain equipment like disconnect switches. For 4" or 5" boxes at that voltage they're not required. If your job has all full punched KOs they are not required.
Eddie702
Licensed Electrician
- Location
- Western Massachusetts
- Occupation
- Electrician
They are required on services
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Are they? What about a bonding locknut?
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
The requirements at services regardless of voltage are essentially same as the requirements for over 250V. The way I read it grounding bushings (or something equivalent) are only really required around concentric and eccentric KOs. I don't regard a bonding locknut as okay for those KO situations. Otherwise, a grounding bushing is not strictly necessary on metallic enclosures, although putting one in allows you to ignore the question of whether you adequately removed paint (250.12).
In my work the most common real reason that grounding bushings are required is passing through non-metallic equipment enclosures. Otherwise, the answer to the OPs question is No, they are not usually installed at both ends if a wire EGC is run.
Some should post the flow chart again.
TwistLock
Member
- Location
- California
- Occupation
- Electrician
- Location
- New Jersey
- Occupation
- Journeyman Electrician
For a service raceway a bonding bushing would be required for concentric or eccentric KO's. For full punched KOs there are other options like a bonding locknut or wedge. Bonding bushings are not required for all services.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Would it be accurate to say that the conduit itself may be bonded at only one end, but a means to do so must be provided for at both ends, because it's a box requirement, not a conduit requirement?
Yeah if I was using that chart in a code class I'd probably change it to look like this:
