CH decided to fail today - chose a nice Spring day, so I can't complain too much.
Pump body is hot, far hotter than it should be with no gas burning (integrated combi Vokera)
There's a great big capacitor in the connection box, scorched and split open.
If I cut it out of the circuit, will the pump run until I can replace it?
Do the connections need to be joined for that?
(Bizarrely, the fault code is d1, condensate trap blocked. But I've dismantled and checked that)
Thanks if any can advise?
No. It's a motor start or run capacitor. The motor needs it to start turning. The motor will be hot because it is not turning and is hence drawing a higher current than normal.
Hopefully the body isn't too scorched to read the specification as you need to replace it with a capacitor intended for motor start or run use (as appropriate) with the same capacitance and voltage rating.
It is important not to use a polarised capacitor intended for DC use (will have + and - marking on terminals) in an AC motor application.
Yes it is used to phase shift the supply to start it running in the right direction as far as I can recall. It might of course itself, ie the motor that caused a problem so it might be best to replace the module rather than faff about just replacing the capacitor. Brian
Thanks Graham - so the winding acts as a heater element instead of turning?
I've located what seems to be a suitable match (ebay 251275119724)
2.5uf, 2.5mfd, Motor Run Capacitor, Bipolar 400v, 450v, 50/60 Hz, - a cheap fix at £7.29, if it works out.Much appreciated.
Thanks Brian - I tested the resistance of the motor as suggested here -
My £5 multimeter read a steady 180 Ohms, and the impeller shaft spins smoothly, so I have my fingers crossed.
If I have to change whole pump it's not so bad, but obviously hoping not to.
£7.29 for a 2.5uF cap, ye gods. At that price I'd raid the junkboxes to a ssemble 2x 5uF 400v caps in series.
NT
Does seem a bit overpriced. Rapids are about £2.50 + postage.
Rapid don't have a cheap 2.5uF but I expect 2 or 3uF would do almost as well - provided that it isn't that the motor has completely seized up.
You could, if you don't mind the risk of a couple of aging electrolytics with insufficient ripple current rating exploding. Most people would prefer to fit the proper part for the job and think that £7-odd was a well-spent alternative to a boiler call-out fee.
Why would you use lytics? Why would you fit an underspecced part? Honestly.
NT
Thanks, I'll save that link - but to be honest, I'm not unhappy with £7 through the letterbox tomorrow. We have no heating, I'm tied up working long hours and can't easily get to a parts supplier, so it works out OK.
Fingers crossed!
If you've got a junkbox with spare motor-rated capacitors, fine. Use them.
If your junkbox has an electronics focus then keep your 400 V electrolytics for valve use, not motors.
I dont
800v non-self healing is fine for motors, unless you can come up with a sen sible reason why not.NT
So you don't have correctly specced parts.
If you want to use a component for an application it is not rated for, or sold as suitable for, it is up to you, not me, to decide if it is suitable for that application.
Back of the net!
Hooked the new capacitor up temporarily with Wago lever connectors, waited a minute for it to absorb some charge and everything started up lovely.
One last (self-inflicted) question. How long for the cap to discharge before I can permanently join it up with solder and heatshrink sleeving? If I take it out of the circuit and leave it for an hour, or more? Is there a safe way to discharge the stored energy?
Thanks to Graham & Brian for the brilliant help!
As` it's connected to AC, not long, as the charge reverses 100 times a second in service. Just leave it connected to the circuit for a few moments after you try to start it with the power off.
It should discharge immediately on power-off through the motor windings. You can check that has happened with your £5 multimeter. Set it on a
300 - 1000 Volt DC range and put the probes across the capacitor. If there is an appreciable reading it should discharge over a couple of minutes if you have a digital meter, or much faster if it is an analogue model.You don't need to wait for the capacitor to absorb charge. This is a mains AC application so the capacitor is charging and discharging twice per cycle, hence 100 times per second.
You're welcome. Thanks for the feedback.
Steve Walker formulated the question :
I don't quite understand the 'leave a minute to charge up'.
These things normally discharge very quickly, if you doubt it, just short the terminals with a screwdriver etc. to discharge it.
The normal wiring of the run capacitor prevents it storing a charge when the motor supply is turned off/disconnected. About the only way of realising this risk (up to a max of 350ish volts) is to disconnect the cap whilst the motor is live and running, not something anyone is likely to do unless they're 'experimenting' (in which case, they aught to be well aware of this risk).
wrong
I did. Then you decided standard 800v plastic film wasnt suitable, so you t ell us why. Its that or hot air.
NT
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