CH pump problem?

Great site! Maybe I can pick someone's brain for some advice...

I think there may be something wrong with my CH pump. I have a Baxi gas boiler in my bathroom controlled by a timer in my kitchen. When I set the timer to heat the water and/or the CH there is no problem, the water in the tank/radiators gets hot as required.

However, when I switch off the CH and hot water heating, there is still the slight gurgling of circulating water in the system and a distinct faitn whirring, as if the pump is continuously *on*. I noticed this around 8 weeks ago and now have some free time to investigate further. At the moment I am turning the boiler thermostat wheel to 'off' when it is not required for the hot water etc.

Even though the boiler is 'off', the water passing through the pipe either side of the pump is somehow still hot.

So I am wondering whether I simply need to replace the pump... or the electronic timer... or the boiler? The pump was only replaced about three years ago. The boiler is at least 20 years old but has given no problems.

WHat's the boiler, some hold the pump on for a while after the boiler's stopped to make sure it doesn't overheat ("Pump overrun").
Are you sure the pump doesn't go off at all?

Obviously I am not an expert, but the pipes are continually hot between the boiler, the pump, and back to the boiler. I can feel a slight vibration when I touch the pump - I realise pumps normally run very smoothly and they often don't give obvious signs they are running, unless they have air in them etc.

There is definitely the sounds of water circulating and I assume this would not be the case if it wasn't being pumped in some way.

What I find strange is that the boiler thermostat is set to 'off' at the moment, so I would have expected only the pilot light to be on. Then how is the water in the pipe getting hot?!

I haven't used the hot water for two days now, because of the tropical weather here

If the boiler has a pilot light then this contributes about 200 watts of heating and the pump another 80 watts.

This can cause the pipe to be warm although not actually hot unless the boiler is coming on occasionally to heat it up.

Tony

You need - obviously - to check where the pump is powered from.
Then find the boiler model..

Okay. Boiler model is either a Baxi WM 531 RS or a WM 401 RS

The pump is a Grundfors Selectric.

The wire from the pump feeds into a junction box which is, in turn, connected via a switched fuse box to the mains. I have turned the power off at the switched fuse box and the pump has stopped. Hoorah!

Now, if you hear a loud explosion in the South Wales area you will know someething has gone wrong