Feeder Breaker Sizng for Dry type transformer

[HamidEle]

I am sizing a feeder breaker for a 112.5KVA Transformer(600v/208v). As per Canadian Electrical Code.The primary breaker shall be sized not larger than 1.25FLA (Pri)if the secondary breaker is sized larger than 1.25FLA(sec).Therefore I chose 150A FDB cutlerhammer Circuit breaker.But it is also noticed that this breaker may trip on inrush current(12FLA). In this case. can we choose a larger size of CB, like 200A. or alternatively, we can choose a different type of CB with adjustable digit trip unit.

Any inputs would be appreciated.

 

[rbulsara]

Historically, breakers sized per NEC have been proven adequate for standard dry type transformers.

Rafiq Bulsara

http://www.srengineersct.com

 

[rbulsara]

NEC or CEC.

Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

FLA = 108 Amp
12FLA = 1300 Amp
150 Amp breaker @ 10X instantaneous setting = 1500 Amp.
Another option may be to down size the secondary breaker to 1.25FLA(sec)

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HamidEle]

12FLA = 1300 Amp
FDB 150 Amp breaker has a fixed characteristic. The instantaneous settings range between 800A and 1600A.

 

[waross]

Yes.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[alehman]

150 is probably OK if you set the instantaneous up.

Alan
----
"It’s always fun to do the impossible." - Walt Disney

 

[automatic2]

the code refers largely to wire ampacity when describing when and of what size of protection is required. You do not mention wire capacity, so sizing of protection is mute.

 

[rbulsara]

NEC (and CEC I presume) has specific requirements (limitations) on transformer protection as well.

Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

Yes Rafiq, CEC also. Wire ampacity protection tables are for use where not otherwise specified.

Bill
--------------------
"Why not the best?"
Jimmy Carter