TRANSFORMER SECONDARY GROUND

Status
Not open for further replies.

ohmhead

Senior Member
Location
ORLANDO FLA
Question transformer with 25 feet or less to panel from transformer electrical inspector says the normal branch circuit ground in raceway is not big enough.

The normal branch table 250.122 equipment grounding conductors for grounding raceway and equipment he says this is wrong that the ground in the raceway must be larger and we need to use 250.66 for the secondary feeders from any transformer.

He wants this larger ground run inside raceway with secondary feeders from each transformer .

Because there unprotected he says these transformers are not the service these are internal down stream transformers in different locations in this building they are not the service to building .

Can you tell me why ? Or if this is actually a code issue because for many years it was 250.122 and we never had a issue .

The electrical engineer has on the one line the normal sized equipment grounding conductors running with the feeders in these raceways .

Please let me know what you think
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
IF I understand correctly, you are referencing the "ground" from the transformer secondary to the transformer secondary panel(s). If that is correct, 250.30(A) {'08 Code}, requires the system bonding jumper and equipment bonding jumper to be sized per 250.102(C) which does indeed require sizing per 250.66
 

ohmhead

Senior Member
Location
ORLANDO FLA
IF I understand correctly, you are referencing the "ground" from the transformer secondary to the transformer secondary panel(s). If that is correct, 250.30(A) {'08 Code}, requires the system bonding jumper and equipment bonding jumper to be sized per 250.102(C) which does indeed require sizing per 250.66

Augie this is not the bonding jumper this is the equipment ground we install with the feeders ABCN in raceways thats what he is telling us needs to be larger then the engineer plans per electrical engineer .
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
sorry, I'm still not clear.. must be a drug night,,
are these "feeders" from the transformer secondary terminals or a overcurrent device ?
 

ohmhead

Senior Member
Location
ORLANDO FLA
sorry, I'm still not clear.. must be a drug night,,
are these "feeders" from the transformer secondary terminals or a overcurrent device ?

Ok lets start from here . And YES

500 kva transformer the secondarys are per plan 6 runs of 600 mcm ABC now the neutrals in each raceway is a 200 percent neutral 600 mcm and the equipment grounding conductor is a single 400 mcm in each raceway of the group of 6 runs . note the equipment ground is run in each of the 6 raceways

Each transformer has a secondary disconnect which is a 1800 amp trip 2000 amp frame brk .

What the Elec Inspector doesnt like is the 400 mcm equipment ground he says it should be larger in each of the 6 runs from transformer to disconnect .
 
Last edited:

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Ok lets start from here . And YES

500 kva transformer the secondarys are per plan 6 runs of 600 mcm ABC now the neutrals in each raceway is a 200 percent neutral 600 mcm and the equipment grounding conductor is a single 400 mcm in each raceway of the group of 6 runs . note the equipment ground is run in each of the 6 raceways

Each transformer has a secondary disconnect which is a 1800 amp trip 2000 amp frame brk .

What the Elec Inspector doesnt like is the 400 mcm equipment ground he says it should be larger in each of the 6 runs from transformer to disconnect
.

The conductor in each raceway is sized based on 250.66 and the conductors in each of the parallel raceway not the combined total of all of the parallel conductors. Look at 250.30(A)(2) which directs you to 250.102(C) last sentence. All you need is a #3/0 Al conductor in each parallel raceway.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
(side note (6) runs of 600.... are we talking AL ? )

I still see this on the secondary of the transformer AHEAD of the OCP device so we are talking 250.66, however, he would be real unhappy if I installed that system as 250.30 > 250.102(C) states "where multiple raceways are used....the size shall be based on the conductor in each raceway" so my install would be 600's with a 3/0 equipment bond jumper.
I may be making an idiot of myself so I will bow out for others to comment.

edit: I think Infinity and I are saying the same thing.. hopefully :)
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
(side note (6) runs of 600.... are we talking AL ? )

I still see this on the secondary of the transformer AHEAD of the OCP device so we are talking 250.66, however, he would be real unhappy if I installed that system as 250.30 > 250.102(C) states "where multiple raceways are used....the size shall be based on the conductor in each raceway" so my install would be 600's with a 3/0 equipment bond jumper.
I may be making an idiot of myself so I will bow out for others to comment.

edit: I think Infinity and I are saying the same thing.. hopefully :)

Yes we are. :happyyes:
 

ohmhead

Senior Member
Location
ORLANDO FLA
Thanks for the response i agree with your answers there is a primary breaker and there is a secondary breaker we just do not see why he wants a larger equipment grounding conductor with each paralleled run .

The engineer see,s a 3/0 also as we do .

When we get the final issue resolved this week ill let you know what happen i feel the electrical engineer will win the battle .

Thank you for your input .
 
Status
Not open for further replies.
Top