When I asked about starting capacitor values at the local motor repair shop,
I was told that 500uF per HP is the correct size/value.

Many of the fractional HP motors that I've serviced all seem to follow this
same guideline.
The marked values of about 110uF for 1/4 HP, 140uF for 1/3 HP, etc.

FWIW, the actual measured value will vary considerably from the value marked
on the capacitor case, as the capacitance value tolerance can be 20%.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"RoyJ" wrote in message
m...
A friend came by with a non functioning olde 1 hp motor the other day. A
quick check showed no starting circuit (bad cap or bad centrifugal switch).
Pulled the old cap out, it is the old style aluminum case, NO MARKINGS.

So what size cap to put in?? I just picked a ~200mfd and called it good
but I don't think that is the right answer. So what/how is the cap sized?
Too small a cap and it won't do anything useful. But is bigger better? Or
is the cap matched to the motor in a resonant circuit?

Motor in question is a Westinghouse 1hp 120/240 motor. Judging from the
grease caps, case style, paint color, etc, I'd guess 1940's, maybe early
50's.