If I have my Secondary protection on a Transformer at 125% am I allowed to upsize my Primary OCPD up to 250% no matter what or do I need to meet any more requirements. Long story short I have a 15 KVA 480v Single Phase Transformer good for 39.4 amps with 125% rating if I wanted to upsize the breaker to 50 amps instead of a 45 (for availability reasons) would I be able to if my wire is sized accordingly even though its 2 sizes up being 40 and 45 amp breakers?
Transformer Primary 250% max with Secondary protection?
- Thread starter kjroller
- Start date
My main question here is if I wanted to could I use 1.5 for a multiplier for inrush since 2.5 is the max? And secondary protection the only requirement for me to be able to do that?
With 125% secondary protection (next size up allowed), you can use any size primary protection up to 250% of primary current (next size up not allowed)
The only disadvantage is your primary conductor size is based on that protection.
The only disadvantage is your primary conductor size is based on that protection.
Do you have these swapped for secondary side nec states the conductor must be equal to or greater the ampacity of the conductor. Primary does not have that requirement I believe next size up is ok
I was addressing Art 450. When using 250% primary protection, the secondary (`125%) can be protetcted by the "next size" up whereas the primary can not have the next size up rule apply.
As far as conductor protection, Art 240, the secondary conductors must have an ampacity equal or greater than the secondary OCP device.
I see nothing prohibiting the primary conductor being sized per 240.4
As far as conductor protection, Art 240, the secondary conductors must have an ampacity equal or greater than the secondary OCP device.
I see nothing prohibiting the primary conductor being sized per 240.4