Bushing

[Alwayslearningelec]

So does the M in MIGB stand for metallic or malleable. If using EMT which type of grounding bushing material would most likely be used?

 

[LarryFine]

So does the M in MIGB stand for metallic or malleable.

The latter, if I'm not mistaken; malleable iron.

If using EMT which type of grounding bushing material would most likely be used?

Steel would be my choice, just like the connector.

 

[Alwayslearningelec]

So another related question. So if a grounding bushing is required would it HAVE to be at every box, enclosure etc. the conduit "terminates" at or possibly only at specific point along the run? So some locations along the same run could have a regular bushing and some could have a grounding?
]

 

[infinity]

So another related question. So if a grounding bushing is required would it HAVE to be at every box, enclosure etc. the conduit "terminates" at or possibly only at specific point along the run? So some locations along the same run could have a regular bushing and some could have a grounding?
]

Grounding bushings are rarely required. Do you have a specific type of installation that requires them?

 

[LarryFine]

It depends on a combination of the voltage and the knock-outs.

 

[electrofelon]

So another related question. So if a grounding bushing is required would it HAVE to be at every box, enclosure etc. the conduit "terminates" at or possibly only at specific point along the run? So some locations along the same run could have a regular bushing and some could have a grounding?
]

Not necessarily every box. Think of a MIGB as possibly being needed at a connector/ box/cabinet, like Larry said depending on the voltage, if it's a service, and if it's got concentrics. It may be needed at some terminations and not others - unless it's a service then you need one at every connector (well some additional bonding, could be a BL or wedge).

 

[Alwayslearningelec]

Grounding bushings are rarely required. Do you have a specific type of installation that requires them?

No.

 

[jimport]

Wondering is this is driven by job specs more than NEC. The Trade Hounds app shows many installations with ground bushings even in punched KOs and below 250 volts.

 

[infinity]

So does the M in MIGB stand for metallic or malleable. If using EMT which type of grounding bushing material would most likely be used?

I prefer die cast. They seem to have more precision when it comes to the threads.

 

[kwired]

So another related question. So if a grounding bushing is required would it HAVE to be at every box, enclosure etc. the conduit "terminates" at or possibly only at specific point along the run? So some locations along the same run could have a regular bushing and some could have a grounding?
]

The intent of such item is for when there is or possibly could be an impaired bond by a regular locknut for various reasons, it just gives an alternate path that is more assured will be a sufficient path.

A metal raceway entry into a non metallic enclosure or where there is no enclosure wall say bottomless gear or where transitioning from metal raceway to open conductors also would be a place where a bonding bushing very well might be used

 

[Alwayslearningelec]

So what if you get a pull box and punch your own Kos then you would not use a grounding bushing? That makes no sense

 

[jimport]

So what if you get a pull box and punch your own Kos then you would not use a grounding bushing? That makes no sense

The metallic raceway connection would ground the enclosure.

 

[Alwayslearningelec]

Yes but what's the difference between a concentric KO and one you punch yourself because one you need the migb and one you don't correct?

 

[jimport]

The concentric does not have the same amount of material to carry any current. A punched KO is full contact.

 

[infinity]

So what if you get a pull box and punch your own Kos then you would not use a grounding bushing? That makes no sense

Why does it not make sense? The locknut on the raceway or EMT connector makes the metal to metal connection to the box.

 

[Alwayslearningelec]

Why does it not make sense? The locknut on the raceway or EMT connector makes the metal to metal connection to the box.

Yes. Is it a concentric KO one that's partially imprinted to be knocked out? So whether you knock out your own holes or have the concentric you still need lock nuts

 

[infinity]

Yes. Is it a concentric KO one that's partially imprinted to be knocked out? So whether you knock out your own holes or have the concentric you still need lock nuts

Yes you'll need locknuts. Also if the voltage is 208Y/120 or 120/240 even with concentric KO's bonding bushings would only be required on service raceways.

 

[Alwayslearningelec]

Would you need a seprate bushing( whichever type) for this hub?

 

[Alwayslearningelec]

Yes you'll need locknuts. Also if the voltage is 208Y/120 or 120/240 even with concentric KO's bonding bushings would only be required on service raceways.

Yes but I'm referring to the grounding bushing. Did you say that whether the ko's are concentric or punched out yourself makes a difference if a grounding bushing is required??

 

[infinity]

Would you need a seprate bushing( whichever type) for this hub?

No. The insulated throat is all that's required.

Yes but I'm referring to the grounding bushing. Did you say that whether the ko's are concentric or punched out yourself makes a difference if a grounding bushing is required??

What voltage are you referring to? For less than 250 volts to ground a bonding bushing is not required even with concentric or eccentric KO's.