ECN Forum Forums General Topics of the Trade General Discussion Area Transformer protection

I made all of my guys use not only torque wrenches, but we had the torque screwdrivers when we installed a new service. I was getting tired of my guys snapping the lugs on the service meter.

After some struggle I was able to take the breaker OFF and it seems like because of over torque the mounting bolt was striped and the bus bar was damaged which in turn created heat and breaker tripped. (at least that is what it looks like).
So for now I took the breaker OFF and need to track down a hardware kit to be able to mount the new breaker.

By reading the code in detail, i got myself confused:

Does a panel board need a main disconnect if it is within 10' of the transformer?
45 KVA 480 primary with 60A fuses, and 208-120 secondary with 1AWG conductors

I was speaking with a fellow contractor and he said "absolutely required" but when read 240.21 and 450.3 i get confused.

Thanks

IIRC...

You can escape the (master) OCPD in such a situation...

BUT...

You're back to a limit of SIX OCPDs in the panel board.

This last little item effectively means that everyone goes with transformer tap protection, and with the size of secondaries that you're running even 25 feet can be allowed.

Study tap rules and Separately Derived Systems.

Normally a 45kVA three phase will feed a bus protected by 125A OCPD -- or less.

Also study up on exception permitting location of said XFMR ABOVE a 'soft lid.'

The panelboard main device is answer by article 408, not 450 or 240.

450 deals with protecting the transformer.
240 deals with protecting the conductor between the transformer and the panel.

Thank you all for your replies.

The more i learn the more i know how much i didn't know.