Boiler AND pump running with no demand

[sean206]

Hi all!

I've got a weird situation whereby the boiler AND pump (regular domestic system) remain running after the central heating AND hot water have been switched off at the programmer. It's also difficult to start the boiler unless you hit advance on both CH and HW. Once it's running, the boiler/pump will keep running until I turn the boiler itself off.

Any ideas on the cause would be really appreciated!

Thanks in advance

Sean

 

[stem]

A bit more information is required. For example do you have a motorised valve, or valves?

A 3 port valve something like this?

Untitled

• stem
• 1 Apr 2010
• 8

Or 2 x two port valves like this?

Untitled

• stem
• 26 Mar 2010
• 6

 

[sean206]

Thanks for your reply.

It's a 3 way motorised valve; almost exactly as above. It's a Honeywell unit if I remember right.

 

[Agile]

We suspect a fault inside the valve.

There is a micro switch which is used to bring the boiler and pump on.

It may be caused by a faulty switch, a worn or faulty mechanism or a stiff shaft on the valve.

You can check the latter by removing the head and feeling the shaft which should turn fairly easily with two fingers.

But you can ONLY remove the head on the later valves which have a dimple like the top one in the picture!

Tony

 

[sean206]

Interesting!

Thanks very much for the feedback! I'll have a look at it tomorrow!