Sizing wire for bonding to structural metal and metal water piping systems

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Jennifer K.

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Hello - I understand NEC table 250.102(C)(1) should be used for sizing the bonding wire to structural metal and metal water piping systems in a building. For what system are we to base the largest ungrounded conductor on for the selection? Is this based on the largest service in the building or the nearest alternating-current system?
 
Jennifer K. said:
I understand NEC table 250.102(C)(1) should be used for sizing the bonding wire to structural metal and metal water piping systems in a building.
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If sounds like you're referring to the GEC which is T250.66 based on the SEC's.
 
ActionDave said:
Are you asking about sizing for a transformer located in the building away from the service?
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Hello - I am referring to sizing the wiring for building structural steel and pipes. Article 250 indicates that NEC table 250.102(C)(1) should be used to size the bonding wire to these items however it is not clear what alternating current system it is based on - the largest service for the entire building or the conductors for the nearest electrical equipment (to that particular steel/pipe).
 
Jennifer K. said:
Hello - I am referring to sizing the wiring for building structural steel and pipes. Article 250 indicates that NEC table 250.102(C)(1) should be used to size the bonding wire to these items however it is not clear what alternating current system it is based on - the largest service for the entire building or the conductors for the nearest electrical equipment (to that particular steel/pipe).
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It is based on the conductors for the separately derived system you are bonding, not anything upstream of that system. Take a typical delta-wye transformer, for example. Anything upstream of that transformer doesn't matter. The bonding jumper would be sized based on the size of the transformer's secondary conductors using Table 250.102(C)(1).
 
This question pertains how to address covering the bonding wire size in general for structural metal and metal water piping systems in a building. Understood these should be bonded per NEC but with what size wire? From my research NEC 250.104(A)(1) provides direction on bonding for metal water piping and indicates the bonding jumpers shall be sized per Table 250.102(C)(1); this table is based on largest ungrounded conductor of an alternating current system so I am trying to understand which system it should be based on (the service?) The code section for structural metal in a building is 250.104(C); this indicates to use that same table for sizing the bonding jumper.
 
Jennifer K. said:
This question pertains how to address covering the bonding wire size in general for structural metal and metal water piping systems in a building. Understood these should be bonded per NEC but with what size wire? From my research NEC 250.104(A)(1) provides direction on bonding for metal water piping and indicates the bonding jumpers shall be sized per Table 250.102(C)(1); this table is based on largest ungrounded conductor of an alternating current system so I am trying to understand which system it should be based on (the service?) The code section for structural metal in a building is 250.104(C); this indicates to use that same table for sizing the bonding jumper.
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Service size determines it
 
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