There's a pump which boosts pressure to the cold circuit (taps, bog
etc) in our house when a tap is turned on.

About 1 time in 5, it won't spin, but just sit there humming. As I
suspected, the electric meter spins pretty quickly when it's stuck
like this!

The main plate on top says:
OSIP Electropompe Tpe VCB45/42
0.33Kw 220-240v 2.5a 8µF
Vc:450 Hz:50 IS.CL:F

Inside, there's a capacitor. It says:
Italfarad - 05/90 (date of manufacture, I'd guess)
RP-3 10040
µF: 10 ±5%b
450V~ DB HPFPU
400V~ DB HPFNT
------------------------------
500V 120/10
400V H250 25/85 360V


So, there it all is! Do capacitors fade over time? Anyway of testing
with yer standard £5 Maplin yellow multimeter?
Any ideas greatly appreciated. Thanks!

In article ,
lardconcepts writes:
There's a pump which boosts pressure to the cold circuit (taps, bog
etc) in our house when a tap is turned on.
About 1 time in 5, it won't spin, but just sit there humming. As I
suspected, the electric meter spins pretty quickly when it's stuck
like this!
The main plate on top says:
OSIP Electropompe Tpe VCB45/42
0.33Kw 220-240v 2.5a 8µF
Vc:450 Hz:50 IS.CL:F
Inside, there's a capacitor. It says:
Italfarad - 05/90 (date of manufacture, I'd guess)
RP-3 10040
µF: 10 ±5%b
450V~ DB HPFPU
400V~ DB HPFNT
------------------------------
500V 120/10
400V H250 25/85 360V
So, there it all is! Do capacitors fade over time?

Yes, although it's sometimes obvious due to the guts spewing out.
The capacitor failing will result in reduced (and eventually no)
starting torque.

Anyway of testing with yer standard £5 Maplin yellow multimeter?

Yes (actually, don't even need a meter).
Impedance of an 8µF capacitor is about 400 ohms (at 50Hz).
That's also about the resistance of a 150W mains light bulb.
Temporarily remove the capacitor from the motor. Find a 60W
or 100W light bulb (filament), and wire it up to the mains in
series with the capacitor. (If the capacitor has a metal case,
for safety's sake, assume it could be live during the test.)
The bulb should light up at significantly reduced brightness,
and if left on for a while, the capacitor should not get hot.
The capacitor is dead if the light doesn't light at all, lights
at full brightness, or the capacitor gets very hot.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

lardconcepts wrote:

So, there it all is! Do capacitors fade over time? Anyway of testing

They can...

with yer standard £5 Maplin yellow multimeter?

A non exact test is to use an ohms range - when you probe the cap out of
circuit (make sure its discharged first) you should see a reading that
starts low and then rapidly rises, swap the leads round and it should
repeat. Much more satisfying on an analogue meter it has to be said. It
won't give you a reading of the actual capacitance some posh analogue
meters can do that for small caps, or a LCR meter is needed for larger
ones), but it will give you an indication that it is at least
functioning - and you can compare the behaviour against a known good one.

--
Cheers,

John.

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On Wed, 12 Aug 2009 02:51:14 -0700 (PDT), lardconcepts
wrote:


So, there it all is! Do capacitors fade over time? Anyway of testing
with yer standard £5 Maplin yellow multimeter?

They generally fail rather than fade. It is a motor run capacitor on
that motor, not a motor start, so it is in circuit all the time and if
faulty you would also get a lot of motor vibration when running as
well as starting problems.

If the fault is intermittent starting I'd look first at the pump and
bearings - is it binding at all? Induction motors have relatively
poor starting torque and a small obstruction can prevent them starting
reliably.

On Aug 12, 5:31*pm, Peter Parry wrote:

If the fault is intermittent starting *I'd look first at the pump and
bearings - is it binding at all? *Induction motors have relatively
poor starting torque and a small obstruction can prevent them starting
reliably.

Well, thanks all - capacitor checked out fine, and I learnt why a
capacitor is used to run an induction motor - to create an offset
voltage so it knows which direction to twiddle!
I'd forgotten all about that...

Anyway, turns out to be stickyness - the cooling fan on the end was
running, so I pulled the fan back to where it looked like it used to
rest on the shaft, then it started leaking water.
An hour later, I'd taken the whole damn lot out, plumbed it straight
through, and without all the gubbins in the way, the water flow is
better anyway! (Still not quite pumped level, but perfectly
acceptable).

The whole thing was a complete bodge anyway - no idea who did it, but
it's gone now!

Thanks for all the help and advice.