Pump faulty?

I have a Potterton Puma 80 combi which for some time now has not been heating the 8 radiators properly in the house. It takes hours for some radiators to warm up and I have noticed that the return pipe to the boiler (22mm) never gets all that hot.

I have recently balanced the radiators but it still takes hours for all the radiators to warm up. After about a week or so, however, it was back to its usual problems where some radiators would go cold after warming up.

I spoke to a plumber and we suspected that there may be a problem with the central heating pump. As an experiment I completely removed the large black octagonal plastic screw from the pump and water and steam came out across the room at some incredible rate.

The pump itself has now been removed and is marked as MULTI HEAD III and appears to be of British Gas make. I have some questions.

Should water come out at pressure if this octagonal screw is removed? I was of the understanding that its purpose was to release air from the system and that it could be removed even when the system is pressurised.

The pump housing is pretty well caked up with a black deposit, would this make a significant difference to the pumps effectiveness? When the pump runs it is pretty well silent as expected.

Regards FarmerJohn

FarmerJohn said:

The pump housing is pretty well caked up with a black deposit, would this make a significant difference to the pumps effectiveness? When the pump runs it is pretty well silent as expected.

Regards FarmerJohn

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Yes. Replace the pump. Its always the first thing to suspect. Although a faulty diverter can give same symptoms but the fact its 'caked' with sludge gives us a pretty good clue.

Thanks for the reply.

It would seem that I have two choices.

I could just replace the motor part of the pump and use the existing housing in the combi. This would be quicker but would be mixing new parts with old.

Or I could replace the entire pump assembly which would take much longer because it is difficult to get at the pump pipe screws and they look quite corroded.

The first option has been recommended to me by a plumber but I suspect I would need to get an exact match on the current pump which I think is a Myson 15/50 or 15/60. Are these still available?

Regards FarmerJohn

The new ones are made by Circulating Pumps http://www.circulatingpumps.net/home.asp

I only ever replace the head. Especially if the unions look corroded![/url]

Many thanks for all the help and the link.

Looking at it I think it would be wise to start with just replacing the head as you suggested.

Is there any recommended cleaner to remove the black crud on the pump housing that is still in the combi?

Regards FarmerJohn

This is a mild strength cleaner which can be left in for weeks and will gradually break it down.

I have ordered a replacement pump, Myson CP63, and will add some of the gung remover that you suggested.

I will post when the pump head has been changed and let you know if my problem has been sorted.

Many thanks for all your help.

Regards FarmerJohn