Main service panelboard

[hhsting]

I have 208/120V main service panelboard with main breaker 400A. The plans show the panelboard ground bus is bonded to the enclosure by manufacturer and the panelboard neutral bus is also bonded to enclosure by manufacturer without main bonding jumper.

I was wondering for those of you actually do the install or actually have seen field install inspection following questions:

1. I have seen panelboard where one bus is bonded to the enclosure by manufacturer and second one usually installed by contractors but not both buses bonded to enclosure by manufacturer. Do panels like one described above exists?

2. Suitable for use as service equipment only panelboard would it normally contain both neutral bar bonded to enclosure and ground bus bar bonded to enclosure? If not then how does it come typically?

3. Suitable for use as service equipment do both ground by and neutral bus come bonded to panelboard by manufacturer?

4. Would panel describe first paragraph suitable for use only as service equipment?

 

[augie47]

If the neutral buss is secured to the panelboard it is likely "suitable for use only as service equipment".
See it fairly often on 200 amp and occasionally on 400 amp.
Neutral and equipment grounding bars would be secured to the panelboard

 

[hhsting]

If the neutral buss is secured to the panelboard it is likely "suitable for use only as service equipment".
See it fairly often on 200 amp and occasionally on 400 amp.
Neutral and equipment grounding bars would be secured to the panelboard

In that case if both neutral bus is bonded to panelboard and ground bus bonded to panelboard by manufacturer then main bonding jumper would not be screw, bus or wire. Does one need to install wire between neutral and ground bus still?

 

[augie47]

NO. As long as you don't terminate neutrals on the equipment ground bar.

 

[hhsting]

NO. As long as you don't terminate neutrals on the equipment ground bar.

Plans are on 11x17 6 looked like 4. The main service panelboard in question post #1 is 600A not 400A.

I don’t understand if both bus are bonded to the panel enclosure then they are electrically connected so why landing neutrals on equipment grounding bus bar is not allowed? Would not this be same situation where main bonding jumper is screw each bar and their is neutral at equipment grounding bar?

 

[kwired]

In that case if both neutral bus is bonded to panelboard and ground bus bonded to panelboard by manufacturer then main bonding jumper would not be screw, bus or wire. Does one need to install wire between neutral and ground bus still?

NO. As long as you don't terminate neutrals on the equipment ground bar.

If they provide a bus or conductor between the two then they are both "neutral" bars.

You can not use the enclosure as a path for neutral current between the two, only can use enclosure for bonding/equipment grounding conductor path.

 

[kwired]

Plans are on 11x17 6 looked like 4. The main service panelboard in question post #1 is 600A not 400A.

I don’t understand if both bus are bonded to the panel enclosure then they are electrically connected so why landing neutrals on equipment grounding bus bar is not allowed? Would not this be same situation where main bonding jumper is screw each bar and their is neutral at equipment grounding bar?

200.2(B) says "The continuity of a grounded conductor shall not depend on a connection to a metallic enclosure, raceway, or cable armor."

This would prohibit use of the enclosure to complete the circuit from one bar to the one with the grounded supply conductor. If you attach a bus or other "conductor" between them then they are parallel via the enclosure but you are not relying on the enclosure as the sole path for normal current flow, just for abnormal conditions when the EGC would be carrying fault current.

 

[hhsting]

200.2(B) says "The continuity of a grounded conductor shall not depend on a connection to a metallic enclosure, raceway, or cable armor."

This would prohibit use of the enclosure to complete the circuit from one bar to the one with the grounded supply conductor. If you attach a bus or other "conductor" between them then they are parallel via the enclosure but you are not relying on the enclosure as the sole path for normal current flow, just for abnormal conditions when the EGC would be carrying fault current.

So let’s say both the neutral bus is bonded to panelboard enclosure and ground bus is bonded to panelboard enclosure by the manufacturer.

However someone in above situation still installs additional main bonding jumper wire or bus between the neutral bus and ground bus.

Afterwards thinking that main bonding jumper wire or bus is provided someone then install neutral at equipment grounding bus bar then it would still not be okay to do this?

 

[hhsting]

If the neutral buss is secured to the panelboard it is likely "suitable for use only as service equipment".
See it fairly often on 200 amp and occasionally on 400 amp.
Neutral and equipment grounding bars would be secured to the panelboard

It’s actually 600A not 400A. Have you seen on 600A?

 

[kwired]

So let’s say both the neutral bus is bonded to panelboard enclosure and ground bus is bonded to panelboard enclosure by the manufacturer.

However someone in above situation still installs additional main bonding jumper wire or bus between the neutral bus and ground bus.

Afterwards thinking that main bonding jumper wire or bus is provided someone then install neutral at equipment grounding bus bar then it would still not be okay to do this?

Said jumper would need to have enough ampacity to carry max expected load it can have on it at very least.

 

[hhsting]

Said jumper would need to have enough ampacity to carry max expected load it can have on it at very least.

Ok but if one of circuit neutral wire is on equipment bar, both bars bonded to panel by manufacturer, and their is additional main bonding jumper between neutral bar and equipment bar, current can still flow thru enclosure which is not allowed no? Let’s say main bonding jumper wire is sized per table 250.102(C)(1) it would not be max and not allowed?

 

[kwired]

Ok but if one of circuit neutral wire is on equipment bar, both bars bonded to panel by manufacturer, and their is additional main bonding jumper between neutral bar and equipment bar, current can still flow thru enclosure which is not allowed no? Let’s say main bonding jumper wire is sized per table 250.102(C)(1) it would not be max and not allowed?

Is no different than having grounded conductor bonded to meter socket enclosure and then running metal raceway between meter and the service disconnect, you will have some parallel grounded conductor current on the metal raceway, but NEC does not see this as objectionable current here.

 

[augie47]

Original question answered.. beyond that is rambling