Combi boiler pump compatibility

[tazman]

Greetings all,
I have a pain in the backside also known as a Biasi Prisma 28 combi which recently stopped firing up. Traced this to the pump not running which I managed to free off and it now works. It's a Salmson item and I would ilke to know whether it might be compatible with a Grundfoss or Myson item. Ideally I'd prefer to leave the housing in situ and just replace the motor unit inc the impellor. It's about 7 years old and isn't noisey or anything.
Thanks in anticipation.

 

[Agile]

If it was seized up then thats progbably due to dirt in the system.

If it is a red one and the boiler is about 1998 manufacture then its a type no longer available and the whole pump has to be changed. Its not that easy because its a 1" flange type.

If its that long shaft type the problem is usually a lack of torque caused by the motor capacitor losing capacitance. If you know what you are doing its often possible to give it a new lease of life by replacing the capacitor.

But as yours was seized up thats dirt in the system.

Tony

 

[tazman]

Hi Tony,
thanks for your response and yes I reckon it is the red pump you describe. However I'm not convinced it was quite seized. I came to that conclusion as the main flow microswitch on the diverter valve wasn't being made. What I did to overcome this was to remove the plug and turn the pump sahft with a screwdriver.
Anyway because I had a little spare time today I removed the pumpmotor and impellor assembly and left the pump body in position. The impellor etc appeared to be quite clean with barely a film of dust or dirt stuck to it. My next move was to run a 240 v supply to the pumpmotor and it appeared to start and run okay.
I am intrigued by the possible capacitor deterioration you describe and would be happy to investigate further or indeed change. Perhaps you could leave me some info on how to??

 

[Agile]

The capacitor is inside the pump connection box.

Its about 2.6 µF and best recovered from another old pump.

You have to make the best connection you can from the old wired to the new one.

Only do it if you feel competent.

You test pump by the finger torque test!

Tony

 

[tazman]

I've refitted the pump and filled the system back up and it's working okay. I expect it will let me down again so I should really try to source a replacement capacitor. Is it the sort of thing that Maplin's might sell as I'm not sure how easy it will be to get one from an old pump. I'm sure the connecting in etc will not be a problem as I can solder the wires and slip some heatshrink sleeving over them.

 

[Agile]

The finger test is done by removing the pump but running it for a few seconds with a finger on the front flat surface of the impeller.

You should be able to stop it with an index finger but hardly with a little finger!

If you like playing with electronics then you can measure the capacitance of the capacitor in the pump and see if its anything like the original 2.6 µF.

An old pump is the easiest place to get a new capacitor. You can try maplins but remember you really need a 440 VAC rating and that will not fit inside the casing. Capacitors in pumps have been designed for that use!

Tony

 

[tazman]

The finger test will be conducted when the bloomin'thing next fails. in the meantime if anyone has got an old pump kicking around with a similar capacitor in it I'll gladly bung them a few quid and postage.