Another grounding wire size question.

[DAB41162]

I have a 100VAC device protected with a 10A class CC fuse.

NFPA 79 Table 8.2.2.3 states that for circuits not exceeding 10A a 16AWG (AWG or kcmil) wire is required.

Also, the control box has an 80A breaker. Does this mean the door and baseplate bonding wires need to be 8AWG?

Is there any justification for using wire sizes other than those listed?

Thank you.

 

[Strathead]

I am confused, is the 80A breaker being protected by a 10A fuse or not. basically, if the metal can become accidentally energized by a wire protected at 80 amps then the ground wire must be based on 80A. If it can only become energized by 10A the a 10A based ground.

 

[DAB41162]

The 80A breaker is for the control panel. the 10A fuse is a branch circuit supplied by a transformer.

 

[Strathead]

The 80A breaker is for the control panel. the 10A fuse is a branch circuit supplied by a transformer.

Then the control panel needs to be grounded with a gound rated for 80A per 250.122

 

[DAB41162]

Then the control panel needs to be grounded with a gound rated for 80A per 250.122

Thank you,
However, what about the size of the wire used to bond the door and the sub plate to the enclosure?

 

[petersonra]

Thank you,
However, what about the size of the wire used to bond the door and the sub plate to the enclosure?

Presumably what you are calling the sub plate is the steel panel the components are mounted on. Normally, at least with US style equipment, these are bonded to the enclosure via paint piercing nuts used to hold the plate in place.

Unless there are energized devices located on the door, I don't recall the for has to be bonded at all.

 

[DAB41162]

Some customers won't accept this type of bonding for the sub plate.

The door can become live via the hinges. Customers typically require this bonding.

Thank you.

 

[petersonra]

Some customers won't accept this type of bonding for the sub plate.

The door can become live via the hinges. Customers typically require this bonding.

Thank you.

If customers require something beyond code they should be sizing it by their own criteria.

I personally don't care what you do, but I don't think you're going to find the answer in some code somewhere because if it's not required there's not going to be any sizing requirements.

If it makes you feel better somehow, just select an arbitrary size conductor to bond the door. Number 10 perhaps.

I did a project one time where the customer spec required a two-ought lug in every junction box. No idea what they were thinking such a large size lug would be needed for but we put them in.

 

[jim dungar]

Some customers won't accept this type of bonding for the sub plate.

The door can become live via the hinges. Customers typically require this bonding.

Thank you.

Typically the door and subpanel/enclosure are bonded based on the size of the protective device that could energize them. For example, everything on the door may be fed by a control transformer with a fuse that might be only a few amps in size. The enclosure and subpanel can be bonded by providing lugs for the incoming 80A ground conductor.