Feeder Bonding Jumper

[bluebuzz81]

Going over practice questions to prepare for master electrician exam and I have a question,

An individual apartment in a multi-family dwelling is supplied by 255-amp THW copper feeders. The feeder conductors are protected by 225-amp breakers from the main 800 amp building service. The water piping systems in the apartment is metal but, tap is pvc. What size equipment bonding jumper is needed?

Shouldn't the answer be #2 copper?

How I came with this, I went to table 310.16 and figured feeder conductor is 250AWG.
Then I went to table 250.102(C)(1) and got #2 from the table.

Answer shows it should be #4.

HELP!

 

[infinity]

What is a equipment bonding jumper?

For a copper feeder the minimum size for 225 amps is #4/0 not 250 kcmil. The EGC for that feeder would be #4.

 

[Dennis Alwon]

It should ask for equipment grounding conductor. This is a feeder so no bonding jumper is needed. The equipment grounding conductor is based on 250.122. Since it is over 200 amp breaker you would need #4 as Infinity stated. The wire size is insignificant in this question.

 

[bluebuzz81]

THANK YOU!