I was looking at a job that had a 225KVA transformer suspended from the ceiling in a large utility room of Building. Below the transformer there are 2 - 400amp disconnects. The secondary conductors go to these two switches. Is this allowed, or do you need one single disconnect? I believe the transformer is 3 phase 480V to 208V. There is a breaker on the Primary side also. Is there a section in the code about the number of disconnects allowed on the secondary side? Thanks
240.21 (C) Each set of conductors feeding seperate loads Shall be permitted to connected to a transformer secondary. (Notice EACH)Devices must be grouped to meet 450.3 (B) note 2 NEC 2005 Handbook Details this clearly on page 170. Yoopersup
The transformer is protected under article 450.3. If the primary disconnect is sized at not more than 125% of the primary FLA, a single disconnect is not required on the secondary.
The secondary conductors are protected by the tap rules in 240.21(C). There are situations where a set of tap conductors can feed multiple devices.
I checked that 240.21 (C) and you were right on with that. We may leave the 2 Disconnects alone and change a distribution panel downstream from those. Stay Safe
