Grundfos CH pump not working

[seank]

Hi everyone, like lots of people I have been sorting out my CH before the cold weather arrives.

This weekend I drained the system, flushed and cleaned two radiators that were not working. We refilled the system, bled the radiators/pump and switched on the CH to check it was working alright. However, though the Baxi boiler seems to be working as normal (pilot light on, fires up OK on command) there is no evidence the pump is working. No vibration, no sound of water circulating. The pipes between the boiler and the pump (and back again) heat up quickly and after a short while the boiler cuts out (I assume because the contents of the pipes have reached a certain temperature - i.e. very hot!). Which is strange - until two days ago *everything* was working normally, except for the two radiators!

The pump is a fairly new Grundfos Selectric, which was replaced about three years ago. The system is controlled by an old (c. 20 years) Honeywell ST499A(?) microelectronic timer. The boiler is a sturdy old (but apparently well functioning) Baxi WM531RS, mounted on the wall adjacent to (but lower than) the water tank and pump. There is a switch in the airing cupboard (next to the pump) which connects/disconnects the CH system to the electrical circuit - currently I have switched that OFF while I cogitate on the problem.

Any suggestions of what might be the problem, before I call in an engineer?

 

[seank]

Maybe I should add that the boiler heats water for the central heating system and/or the hot water (tank in airing cupboard). When we drained the central heating circuit it was not possible to heat the water - neither the pump not the boiler would start when (in our ignorance) we attempted this!

 

[oilman]

Hi everyone, like lots of people I have been sorting out my CH before the cold weather arrives.

No you haven't, it's already here

This weekend I drained the system, flushed and cleaned two radiators that were not working. We refilled the system, bled the radiators/pump and switched on the CH to check it was working alright. However, though the Baxi boiler seems to be working as normal (pilot light on, fires up OK on command) there is no evidence the pump is working. No vibration, no sound of water circulating. The pipes between the boiler and the pump (and back again) heat up quickly and after a short while the boiler cuts out (I assume because the contents of the pipes have reached a certain temperature - i.e. very hot!). Which is strange - until two days ago *everything* was working normally, except for the two radiators!

The pump is a fairly new Grundfos Selectric, which was replaced about three years ago. The system is controlled by an old (c. 20 years) Honeywell ST499A(?) microelectronic timer. The boiler is a sturdy old (but apparently well functioning) Baxi WM531RS, mounted on the wall adjacent to (but lower than) the water tank and pump. There is a switch in the airing cupboard (next to the pump) which connects/disconnects the CH system to the electrical circuit - currently I have switched that OFF while I cogitate on the problem.

Any suggestions of what might be the problem, before I call in an engineer?

Pump not working, could be controller, control valve, pump, something else. We can't see your system, there's a strong possibility there is air in there somewhere.[/quote]

 

[tincup]

Hi


Pump siezed maybe?
Could try to move it manually.

Hope this helps.

 

[seank]

No you haven't, it's already here

No frost here yet. You must be soft or live further North/inland than me

Pump siezed maybe?
Could try to move it manually.

Thanks for the suggestion, tincup.

Someone also suggested to me that there might be sludge in the pump. I imagine there would have to be a fair amount to stop it working! Anyway, looks like I'll have to call in a professional.