When to use bonding bushings?

[FranklinMade]

When do you have to use bonding bushing on raceways entering an enclosure based on the size of the conduit and voltage being used?

 

[infinity]

Conduit size doesn't really matter but over 250 volts to ground might require them. Look at 250.97.

 

[kwired]

Bonding bushings aren't really required, in many instances they are just the most convenient way to provide additional or assured bonding when required.

 

[infinity]

Bonding bushings aren't really required, in many instances they are just the most convenient way to provide additional or assured bonding when required.

Their use is usually contingent upon the type KO's that are encountered and how they're listed.

 

[kwired]

Their use is usually contingent upon the type KO's that are encountered and how they're listed.

True, to some extent. A bonding locknut won't work on concentric ko's. a bonding jumper to an external pipe bonding clamp is one option that isn't unacceptable code wise, just not a popular choice over a bonding bushing. Hence a bonding bushing is almost never "required" but often is the preferred choice.

 

[Dsg319]

Hazardous locations?

 

[kwired]

Hazardous locations?

A lot (maybe even can about say all) of your class 1 equipment will have threaded hubs integral to the enclosures. You generally can't enter anywhere besides where there already is a hub.

Class 2or 3 , you might be using things like myers hubs and general bonding rules would still apply. This application doesn't need to be "explosion proof", just needs to seal out the dust that causes the class 2 or 3 location.

 

[Dsg319]

Class 1 Div2 areas,
A lot situations where the conduit terminates at or just below a cable tray, we will use a bonding bushing to bond the conduit to the cable tray.


Which in return the conduit is bonded again at the enclosure with a bonding style myer hub. Probably overkill bonding at both ends of the conduit, but some company’s spec out certain things like that.

 

[don_resqcapt19]

Hazardous locations?

Yes, the boding required by 501.30(A), 502.30(A), and 503.30(A) extends back to the location of the system or main bonding jumper, which ever comes first on the circuit. These rules prohibit the use of "locknut-bushing and double-locknut types of contacts" for those circuits, requiring some other type of bonding connection or jumper.

 

[kwired]

Yes, the boding required by 501.30(A), 502.30(A), and 503.30(A) extends back to the location of the system or main bonding jumper, which ever comes first on the circuit. These rules prohibit the use of "locknut-bushing and double-locknut types of contacts" for those circuits, requiring some other type of bonding connection or jumper.

Careful reading of that, means if you have non classified location wiring methods ahead of the classified portion, including feeders between main service and a sub panel that the classified location circuit originates, you need to check this bonding to make sure it complies. Particularly applies if the raceway itself is the EGC.

Learned something here, I bet I have violated that before and never knew it was a requirement.

 

[Dsg319]

If I have a distribution panel outside of the classified area that has wiring out to a classified are, with a wire way/trough beneath the panel for conduit terminations.

And have nipples from trough to panel and use the grounding type myer hub with a bonding jumper to the EGC bus, do I have to do that on both sides of the nipple or just one and standard lock nut on the other side?

 

[don_resqcapt19]

Careful reading of that, means if you have non classified location wiring methods ahead of the classified portion, including feeders between main service and a sub panel that the classified location circuit originates, you need to check this bonding to make sure it complies. Particularly applies if the raceway itself is the EGC.

Learned something here, I bet I have violated that before and never knew it was a requirement.

It applies whenever you have a metallic raceway serving a circuit in a classified area, even if there is wire type EGC installed in the metal raceway.

 

[don_resqcapt19]

If I have a distribution panel outside of the classified area that has wiring out to a classified are, with a wire way/trough beneath the panel for conduit terminations.

And have nipples from trough to panel and use the grounding type myer hub with a bonding jumper to the EGC bus, do I have to do that on both sides of the nipple or just one and standard lock nut on the other side?

You have to bond at all connection points on the raceway back to the location of the main or system bonding jumper. It requires bonding at both ends of any nipple or raceway.

 

[kwired]

It applies whenever you have a metallic raceway serving a circuit in a classified area, even if there is wire type EGC installed in the metal raceway.

Within the classified area and up to the origin of the circucit(s) where outside the classified area, yes.

But unless I read it wrong say you have a feeder in non classified areas in metal raceway and then from a panel at the end of said feeder you supply branch circuit(s) in hazardous locations. Isn't it requiring more than just standard locknuts for bonding of the feeder raceway even though it is outside the hazardous location? Especially if the raceway is also the sole EGC for the feeder? Or am I reading a little too much into it?

 

[DrSparks]

You should use bonding bushings any time you think the mechanical connection of a conduit to it's terminal point may not be electrically sound.

Sent from my BE2028 using Tapatalk

 

[don_resqcapt19]

Within the classified area and up to the origin of the circucit(s) where outside the classified area, yes.

But unless I read it wrong say you have a feeder in non classified areas in metal raceway and then from a panel at the end of said feeder you supply branch circuit(s) in hazardous locations. Isn't it requiring more than just standard locknuts for bonding of the feeder raceway even though it is outside the hazardous location? Especially if the raceway is also the sole EGC for the feeder? Or am I reading a little too much into it?

Yes, up to the point of the main or system bonding jumper, whichever may apply. If the circuit originates at a panel that is supplied by a feeder, the bonding must also be applied to the feeder conduit even where the feeder is 100% outside of the classified area.

 

[Strathead]

I think there is a requirement in 430 for bond bushings at services. Don't have time to look.

 

[NTesla76]

@Carultch, I believe, made a really handy flow chart. It's pretty good.