Ignoramus9394 wrote:

What I am curious about is, can I simply use motor rated fuses on both
incoming 240V legs? That should provide all necessary protections for
the idler.

I do not mind installing an overload relay, as such, except that it is
a cost issue. Fuses are cheaper. (unless I can find something at that
junkyard). Realistically speaking, the idler is not going to bind. If
contacts to capacitors break, yes, I could have a stall issue, which
would be addressed by properly sized fuses.

A relay is more exciting and possibly a little more convenient (it is
resettable, I do not need to buy new fuses when a fuse burns out), but
in reality will provide about same protection.

Am I mistaken?


The overload units in a motor starter are have a very narrow operating
range like 57.5 - 61.3A that can be very closely matched to the motor
rating. Picking between a 50-60-70A fuse doesn't give much protection.
Also overloads are designed to allow the starting inrush and are
designed to match the thermal characteristics of the motor for overload.
Even time delay fuses have to be much larger than the motor rating or
they will blow on the starting inrush. Fuses can be sized at up to 175%
of the motor rating and circuit breakers up to 250%(NEC). The fuses in a
motor circuit are intended to provide short circuit protection, not
overload protection.

Bud--