WA_Sparky
Electrical Engineer
- Location
- Vancouver, WA, Clark
- Occupation
- Electrical Engineer
Long story short, I just finished working on a TI restaurant renovation project. All appliances are 208V 3Ø, landlord shell drawings indicated landlord would provide power to space. Found out later in the project (after architect finished design) that we were expected to house the step down delta transformer in our space. Per code without changing rated walls and enclosing the transformer in its own space, a 112.5KVA xfmr was needed. Loads are fine as they are around 200A demand. 112.5KVA outputs roughly 312A, I specified A 400A panel w/ 300A MCB. Contractor referenced the code book and said OCPD could be 400A per NEC.
The only location we could find to put this transformer was in a corner of the store managers office.
My question to you guys is clarification on the NFPA 70E 450.3(A) code.
What defines a supervised location?
In my opinion a supervised location is a locked area that only maintenance personal or licensed electrical worker can access. Is this up to the building official to decide one way or another?
If considered supervised, the secondary OCPD of the transformer can be sized for 250% of its rated current. Otherwise the “any location” installation allows secondary OCPD to be max 125% of xfmr amperage (390A or less). I went with the safer approach and made sure the secondary OCPD was 300A or 350A. I'm just curious for future projects. Thanks in advance!
The only location we could find to put this transformer was in a corner of the store managers office.
My question to you guys is clarification on the NFPA 70E 450.3(A) code.
What defines a supervised location?
In my opinion a supervised location is a locked area that only maintenance personal or licensed electrical worker can access. Is this up to the building official to decide one way or another?
If considered supervised, the secondary OCPD of the transformer can be sized for 250% of its rated current. Otherwise the “any location” installation allows secondary OCPD to be max 125% of xfmr amperage (390A or less). I went with the safer approach and made sure the secondary OCPD was 300A or 350A. I'm just curious for future projects. Thanks in advance!