Migb when required
- Thread starter nickelec
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I don't think it is ever "required" in the way you might be thinking.
If I understand what a migb is, it is just a grounding bushing that includes the plastic wire protecting throat. Sometimes a grounding bushing is required by code, sometimes the plastic throat. If both are required at the same place a bushing that has both features would be handy.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
There is a code reference for bonding both ends of a metallic pipe with a GEC in it and a pipe with a #4 or larger may require a bushing or insulated throat fitting, as was stated above, but there is no set rule requiring a "MIGB" that I know of.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Concentric KO's over 250 volts to ground are one of the few places where they are required.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
That is an option to satisfy the rule, but I do not think that an MIGB is required per se, no? Other methods could be employed.
Did not look up exact rule, so I could easily be shooting myself in the foot here.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
That is an option to satisfy the rule, but I do not think that an MIGB is required per se, no? Other methods could be employed.
Did not look up exact rule, so I could easily be shooting myself in the foot here.
I don't think it is "required" but it is the most practical solution to the actual requirements.
A metal bushing on the threaded end of RMC/IMC is permitted to forego an inside-the-enclosure locknut... provided an exterior locknut is used and wrench tight. In most cases, you cannot do this with the male threaded end of a connector of any wiring method. There is often not enough internal thread in the bushing to solidly bond the enclosure wall between the connector flange and bushing. The test is being able to make it up wrench tight and not be able to spin the connector with the wrench on either side afterward.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
That is an option to satisfy the rule, but I do not think that an MIGB is required per se, no? Other methods could be employed.
Did not look up exact rule, so I could easily be shooting myself in the foot here.
On concentric and eccentric KO's over 250 volts to ground it's the only game in town. You cannot use the other approved fittings bonding locknuts or bonding wedges with those KO's.
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