transformer outside

Status
Not open for further replies.
H

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
I have customer owned transformer outside whose primary is supplied by electric utility. The secondary conductors go to into the building to 1600 amps switchboard 480/277V three phase. Now the switchboard does not have a main breaker. I think its 240.21(4) that says you got to have breaker at the termination but I am not sure if this section would apply. I am confused between 240.21(4) or 225.31 or maybe somewhere in 230. Anyone know which section would apply here?
 
hhsting said:
I have customer owned transformer outside whose primary is supplied by electric utility. The secondary conductors go to into the building to 1600 amps switchboard 480/277V three phase. Now the switchboard does not have a main breaker. I think its 240.21(4) that says you got to have breaker at the termination but I am not sure if this section would apply. I am confused between 240.21(4) or 225.31 or maybe somewhere in 230. Anyone know which section would apply here?
Click to expand...

230.70 would be one place to look, Table 450.3(A) is another. You do not mention if you have OCP on the primary and or secondary sides of the transformer and if there is, what is their location in regards to the building in question. Also, how many OCP devices are in the switchboard, if 6 or less they might all be considered "mains". Need complete information to fully answer this.:angel:
 
ronmath said:
230.70 would be one place to look, Table 450.3(A) is another. You do not mention if you have OCP on the primary and or secondary sides of the transformer and if there is, what is their location in regards to the building in question. Also, how many OCP devices are in the switchboard, if 6 or less they might all be considered "mains". Need complete information to fully answer this.:angel:
Click to expand...
There are 4 breakers in the switchboard. Secondary conductors entering building do not have any overcurrent protection. Now as to the primary yes but not sure of size if thats what you are going to ask. Primary protection I am not sure who provided its existing. However these are outside secondary conductors entering building from outside customer owned transformer.
 
hhsting said:
There are 4 breakers in the switchboard. Secondary conductors entering building do not have any overcurrent protection. Now as to the primary yes but not sure of size if thats what you are going to ask. However these are outside secondary conductors entering building from outside customer owned transformer.

Sent from my SM-G935U using Tapatalk
Click to expand...

Who actually has control over the tranny? Customer bought and owns it but may not have control of it.
 
jumper said:
Transformer. These transformer secondary conductors may be service entrance conductors.

If so, then 230.71 comes into play.
Click to expand...
It doesn't matter, either 225.33(A) or 230.71 apply and they both permit up to 6 disconnects. However the transformer secondary rules in 240.21(C), as far as the location of the OCPD, apply if the conductors in question are on the load side of the service point.
 
jumper said:
Transformer. These transformer secondary conductors may be service entrance conductors.

If so, then 230.71 comes into play.
Click to expand...

Meant to say Service Conductors.

Service Conductors. The conductors from the service point to the service disconnecting means.

My guess is the service point is at the secondary of the transformer. So, even if the transformer is customer owned, service conductors are under 230 and 230.71 applies.

More details would be helpful in trying to answer.
 
Status
Not open for further replies.
Top