fradchaflick
Member
- Location
- Gainesville, FL
The project I'm working on has a automatic door opener that will require 120V/1PH Life Safety power.
The nearest and most practical Life Safety power source is 480Y/277V.
The plan so far is to provide a small, 750VA step-down transformer near the source (using #12 primary and secondary conductors) just to serve the small, automatic door.
The intent is to provide a GEC from the secondary neutral to the nearest structural steel.
Are there any allowances in NEC that will will let the GEC from the secondary side of the transformer be smaller than #8 copper (250.66)? It seems odd to have a GEC several sizes larger than the phase conductors.
System bonding jumpers aren't required to be larger than the neutral conductor (250.30(A)(1)except. 2), so I was curious if something similar was allowed for small step-down transformers that aren't supplying Class 1, 2, or 3 circuits.
The nearest and most practical Life Safety power source is 480Y/277V.
The plan so far is to provide a small, 750VA step-down transformer near the source (using #12 primary and secondary conductors) just to serve the small, automatic door.
The intent is to provide a GEC from the secondary neutral to the nearest structural steel.
Are there any allowances in NEC that will will let the GEC from the secondary side of the transformer be smaller than #8 copper (250.66)? It seems odd to have a GEC several sizes larger than the phase conductors.
System bonding jumpers aren't required to be larger than the neutral conductor (250.30(A)(1)except. 2), so I was curious if something similar was allowed for small step-down transformers that aren't supplying Class 1, 2, or 3 circuits.