Transformer Secondary
- Thread starter websparky
- Start date
- Status
frenchelectrican
Senior Member
- Location
- Nord'est Wisconsin et Paris France
Re: Transformer Secondary
but i have one question here but i did came up some figures but with 150 KVA transformer set up and secondary side is 416 amps i might be wrong on this one but can go up one breaker size like 450 amp breaker on secondary side then can tap to each load centre which it will have 225 amp main breaker or 200 amp breaker in there but really with 200 amp breaker in there i feel it will be pretty close to the limit of secondary conductors can take. i did try to review the NEC code's but i came up the same as bob and don's answer but really i am not too crazy to use the tap unless some kind of busbar.
let me know if i did answer it right
Merci , Marc
but i have one question here but i did came up some figures but with 150 KVA transformer set up and secondary side is 416 amps i might be wrong on this one but can go up one breaker size like 450 amp breaker on secondary side then can tap to each load centre which it will have 225 amp main breaker or 200 amp breaker in there but really with 200 amp breaker in there i feel it will be pretty close to the limit of secondary conductors can take. i did try to review the NEC code's but i came up the same as bob and don's answer but really i am not too crazy to use the tap unless some kind of busbar.
let me know if i did answer it right
Merci , Marc
Re: Transformer Secondary
just a shot in the dark from some one learning.
You could have 3 225 amp main braker panels feed with 4/0 cu all the way to the trans no taps as long as the total caulated load of the 3 panels is less than 416amps. and primary ocpd as high as 450 amp?? trying to learn don't quote me
just a shot in the dark from some one learning.
You could have 3 225 amp main braker panels feed with 4/0 cu all the way to the trans no taps as long as the total caulated load of the 3 panels is less than 416amps. and primary ocpd as high as 450 amp?? trying to learn don't quote me
- Location
- Illinois
- Occupation
- retired electrician
Re: Transformer Secondary
240.21(C)(2) requires that secondary conductors must land on a device with a rating equal to or less than the conductor ampacity. That is not the case here so this rule does not apply. 240.21(C)(6) requires that the secondary conductors terminate on a single OCPD having a rating equal to or less than the conductor ampacity. Again that is not the case here. I thing that there are 3 code compliant options for this installation:
1) the 600s terminate on a MLO panel with a bus rating of not greater than 420 amps and there are three 225 amp breakers installed to feed the panels,
2) the 600s terminate on a OCPD with a rating of 420 amps or less and then the load side of that breaker is tapped with 3 sets of 4/0 to feed the panels, or
3) one set of 4/0 is run from the transformer to each of the?panels and landed on 225 amp main breakers in the panels.
Don
[ January 08, 2006, 07:44 PM: Message edited by: don_resqcapt19 ]
240.21(C)(2) requires that secondary conductors must land on a device with a rating equal to or less than the conductor ampacity. That is not the case here so this rule does not apply. 240.21(C)(6) requires that the secondary conductors terminate on a single OCPD having a rating equal to or less than the conductor ampacity. Again that is not the case here. I thing that there are 3 code compliant options for this installation:
1) the 600s terminate on a MLO panel with a bus rating of not greater than 420 amps and there are three 225 amp breakers installed to feed the panels,
2) the 600s terminate on a OCPD with a rating of 420 amps or less and then the load side of that breaker is tapped with 3 sets of 4/0 to feed the panels, or
3) one set of 4/0 is run from the transformer to each of the?panels and landed on 225 amp main breakers in the panels.
Don
[ January 08, 2006, 07:44 PM: Message edited by: don_resqcapt19 ]
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Transformer Secondary
240.21(C)(1)
240.21(C)(1)
The secondary must have OCD.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Transformer Secondary
Don,
Thanks for your reply!
Do you think that 240.21(B) could be used in this case? Are these not "feeders"? If not, why not?
Don,
Thanks for your reply!
Do you think that 240.21(B) could be used in this case? Are these not "feeders"? If not, why not?
- Location
- Illinois
- Occupation
- retired electrician
Re: Transformer Secondary
Dave,
240.21(B) does not apply because 240.21(C) says "transformer secondary conductor" and specifically covers the installation in question. A feeder has overcurrent protection at its source, and this circuit does not, therefore it is not a feeder.
Don
Dave,
240.21(B) does not apply because 240.21(C) says "transformer secondary conductor" and specifically covers the installation in question. A feeder has overcurrent protection at its source, and this circuit does not, therefore it is not a feeder.
Don
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Transformer Secondary
Thanks, Don!
That is how I thought it had to be also. I just wanted to cover any possible method to be sure.
This PE is a young guy and often his plans are sort of questionable. This is the transformer that started out above a drop ceiling. Now he will have to re-design the secondaries too.
Thanks to all for the help!
Thanks, Don!
That is how I thought it had to be also. I just wanted to cover any possible method to be sure.
This PE is a young guy and often his plans are sort of questionable. This is the transformer that started out above a drop ceiling. Now he will have to re-design the secondaries too.
Thanks to all for the help!
- Status