Is the physical size of a capacitor important? My pool pump is making a
habit of blowing it's capacitor ever few weeks. The best price I can see on
line for this particular model is $75, however a capacitor with a similar
rating, just considerably smaller in size, is around $25.
I'm buying a new pump anyway, however I'd ideally like to get my old one
going just once more so I can clean the deep, dark green colour out of the
water before running the new pump.
So can someone tell me, as I only need it to work once, would a smaller
capacitor of a similar rating do the job?
There are different types of capacitor. It's quite possible to get
identical specced units of different size although a *considerable*
difference in size is unlikely. The fact that the installation is
blowing capacitors regularly points to a fault that needs
Try posting the specs of the two caps up here and someone will better
The capacitor must be AC rated as the same or greater voltage than the
old one and of very similar capacity measured in uF or MF (micro farads)
They are normally referred to as Motor Run capacitors and something in
the range say 5 to 10 uF would cost about 5 UKP here.
Some types have tags on the end suitable for push-on connectors or
soldering to, others will have a few inches of cable moulded into the
body. Most now have an M8 threaded stud on the end for mounting.
Of more concern is why the capacitors are failing so quickly. I would
expect 10 years plus unless it is running too hot by being in thermal
contact with the motor. Maybe consider how/where it is mounted.
Bob in UK
As per the previous posting, capacitors using the same electrolyte, similar
capacitance and similar voltage rating will tend to be a similar can size,
so this suggests we're not comparing like with like.
Probably need to be clear on whether this is a start or run capacitor. A
start capacitor has different characteristics (and I think a different
electroyte) and different range of capacitance. Start capacitors give a
short boost to get the motor fired up but don't remain in circuit (whereas a
run capacitor does, as its name implies).
If this is a start capacitor, it may be that the mechanism to get it out of
circuit once the motor is up to speed isn't working properly (this could be
a relay, centrifugal switch, or electronic switch) and voltage is being
applied to it for longer than it should be, causing premature failure.
As per previous postings, if you post up the details (rating, manufacturer,
part number) it might be possible to find cheaper alternative - $75 seems
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