Bonding Enclosures
- Thread starter fifty60
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
What are you bonding. The equipment grounding conductor is used to bond the panel however if it is a service panel then there wouldn't be an equipment grounding conductor and you have to use 250.66-- the same size as the grounding electrode conductor.
Bonding equipment. Kind of an industrial machine, kind of an appliance, but technically close to lab equipment. The main panel contains a terminal strip for the service ground. We bond equipment with grounding lugs to this same terminal. We also bond any removable service panels to this same terminal....
For the service panels, or anything really, what size conductor should I use for grounding the panels and other equipment? IMO, it should not be less than the service ground conducter....
250.66 is saying #8AWG....
NFPA 79 table 8.2.2.3 basically says the same size as the service ground (same as NEC 250.122)
IEC 61010 says "it shall withstand all thermal and dynamic stresses it could be subjected before one of the overcurrent protective means disconnects the equipment from the supply"
For the service panels, or anything really, what size conductor should I use for grounding the panels and other equipment? IMO, it should not be less than the service ground conducter....
250.66 is saying #8AWG....
NFPA 79 table 8.2.2.3 basically says the same size as the service ground (same as NEC 250.122)
IEC 61010 says "it shall withstand all thermal and dynamic stresses it could be subjected before one of the overcurrent protective means disconnects the equipment from the supply"
Last edited:
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I suspect none of this has anything to do with a "service".
It is almost certainly a branch circuit or maybe a feeder.
It is almost certainly a branch circuit or maybe a feeder.
How does this thing get its power -- directly from the utility, from one of your transformers, or from a feeder? Is there an over current device upstream protecting the conductors to these enclosures? If so, size the bonding jumper per 250.122. Are there enclosures without conductors that you want to bond?
The equipment is connected to a service disconnect on the customer wall. Whatever is supplying the equipment is eventually grounded to the utility service ground (grounded transformer).
Would I have to size it to whatever fuse is on the live conductor that could cause the fault? Some of the equipment on the machine is powered from a 115V connection derived from a transformer located within the equipment enclosure.
I am still working on correct terminology. I consider everything in my equipment that carries the line voltage up until the branch fuses as "the feeder". I understand that this is not truly a feeder, but probably a feeder tap from the actual feeder.
So any conductive surface exposed to the equipment feeder voltage would have to be bonded with a conducter the size of the feeder bonding conductor. Any bonding conductors protection conductive materials in a branch circuit would have to be sized from 250.122 based off of the branch circuit fuse....
Does that seem correct?
Would I have to size it to whatever fuse is on the live conductor that could cause the fault? Some of the equipment on the machine is powered from a 115V connection derived from a transformer located within the equipment enclosure.
I am still working on correct terminology. I consider everything in my equipment that carries the line voltage up until the branch fuses as "the feeder". I understand that this is not truly a feeder, but probably a feeder tap from the actual feeder.
So any conductive surface exposed to the equipment feeder voltage would have to be bonded with a conducter the size of the feeder bonding conductor. Any bonding conductors protection conductive materials in a branch circuit would have to be sized from 250.122 based off of the branch circuit fuse....
Does that seem correct?
Last edited:
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
the problem with not using the correct terminology is that there are different rules for services, feeders, branch circuits, and SDS. They are all similar, but they also have their differences.
service conductors are the conductors coming in from the utility. they stop being service conductors at the service disconnect. it is not impossible for a control panel to be service equipment, but it is uncommon.
I think you mix up concepts between European electrical systems and US electrical systems. it is all electricity so there are a lot of similarities but there are also a lot of differences.
I suspect you are looking for the mythical way to create a universal design to be used every where. at present, there just is no way to do that. the rules are different enough that you can't and should not even try. you can often use the same components though.
what you referred to as a service disconnect probably is not service equipment at all. it is just a disconnect. the circuit is either a feeder or a branch circuit.
equipment grounding conductors associated with either a feeder or a branch circuit are sized according to the rating of the over current protection device protecting that circuit.
the transformer in your equipment is a separately derived system. there is a set of rules to follow for them.
there is no rule requiring exposed conductive parts be bonded with a conductor at all. Just that they be effectively bonded. They can be screwed together and that is generally considered effective.
service conductors are the conductors coming in from the utility. they stop being service conductors at the service disconnect. it is not impossible for a control panel to be service equipment, but it is uncommon.
I think you mix up concepts between European electrical systems and US electrical systems. it is all electricity so there are a lot of similarities but there are also a lot of differences.
I suspect you are looking for the mythical way to create a universal design to be used every where. at present, there just is no way to do that. the rules are different enough that you can't and should not even try. you can often use the same components though.
what you referred to as a service disconnect probably is not service equipment at all. it is just a disconnect. the circuit is either a feeder or a branch circuit.
equipment grounding conductors associated with either a feeder or a branch circuit are sized according to the rating of the over current protection device protecting that circuit.
the transformer in your equipment is a separately derived system. there is a set of rules to follow for them.
there is no rule requiring exposed conductive parts be bonded with a conductor at all. Just that they be effectively bonded. They can be screwed together and that is generally considered effective.
Last edited:
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
What is the voltage of the equipment? Does 250.97
Yes. Anything circuit on the load side of a utility service disconnect requires an equipment grounding conductor (EGC) to be run with the circuit conductors. It is sized per 250.122 which is based on the circuit OCPD rating. All associated non-current-carrying metallic parts are bonded to this EGC, typically by mechanical connection. Where there is insufficient mechancal connection to carry potential fault current levels, a bonding jumper is required.
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