CH & HW Pump keeps running

[RobinJ]

I have a unvented CH & HW system
Boiler is Ideal Classic FF260.

The whole CH and HW system has been working fine, both activating and deactivating on timed control and through room thermostat. I now have an intermittent issue where both HW and CH can be off on the timing programmer and yet the pump remains on. The only way I can stop the pump is to turn off all power to CH system. It usually resets, to function normally after 12+ hours with no power.

I have replaced the CH Timing programmer and has made no change.

Can anyone please offer any guidance to identify what is causing the issue and if its a simple part replacement?

P.S. I have read other threads which suggest it might be either the HW or CH actuator being faulty. But I do not know if this is the case.
One is a 2 port Sunvic LSZ2301 in a plastic case and the other a Honeywell V4043H1056 2 Port motorized valve in a galvenised metal case, but not aware which is HW or for CH.

 

[ericmark]

Likely the micro switch in the motorised valve sticking, some heads can be changed without changing the whole valve.

 

[Harry Bloomfield]

Can anyone please offer any guidance to identify what is causing the issue and if its a simple part replacement?

Modern systems have the boiler control the operation of the pump, so the pump can continue to be called to run after the boiler stops producing heat - Idea is to draw any remaining heat from the boiler to improve its life and increase economy. Might your system be one of those?

Older systems ran both boiler and pump together, only whilst there was a demand for heat, controlled directly by the three port valve actuator.

 

[RobinJ]

Likely the micro switch in the motorised valve sticking, some heads can be changed without changing the whole valve.

Do you believe that the motorised valves sticking is the cause of the pump staying on?

If so, is there a I can identify which one of the valves is sticking?

 

[RobinJ]

Modern systems have the boiler control the operation of the pump, so the pump can continue to be called to run after the boiler stops producing heat - Idea is to draw any remaining heat from the boiler to improve its life and increase economy. Might your system be one of those?

Older systems ran both boiler and pump together, only whilst there was a demand for heat, controlled directly by the three port valve actuator.

Thanks for your response. The boiler is certainly 8-10 years old, maybe more. My issue is that the pump will remain active for hours after last programmed call for action.

Is the 3 port valve actuator normally part of the boiler? The other 2 valves (2 port) I have are next to the HW Cylinder

 

[stem]

You will either have one 3-Port valve. (aka Y-Plan)

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• stem
• 1 Apr 2010
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Or two (or possibly more depending on how many heating zones you have) 2-Port valves (aka S-Plan)

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• stem
• 26 Mar 2010
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Both types have microswitches inside.

 

[RobinJ]

You will either have one 3-Port valve. (aka Y-Plan)

Or two (or possibly more depending on how many heating zones you have) 2-Port valves (aka S-Plan)

Both types have microswitches inside.

Thank you - thanks for the confirmation. I now know I have an S plan system.

As I mentioned in the original posting I have "One 2 port Sunvic LSZ2301 in a plastic case and the other a Honeywell V4043H1056 2 Port motorised valve in a galvanised metal case, but not aware which is HW or for CH."

So does anyone confident to say that this is the likely cause of the pump not deactivating and if so, how do I know which microswitch is failing? Is there a simple test?

 

[foxhole]

Boilers have a run on feature which means when off, the pump will continue to run for a few minutes. Is that what you refer too?

 

[ericmark]

Some makes have just a bleed leaver, this tends to go slack when valve is open, some have an indicator, in the main a programmer supplies the thermostats, and the thermostats supply the valves, and the valves normally an orange wire supply the boiler.

As to pump, some times in parallel with boiler, some times supplied from boiler so it has some run on time.

Since all the orange wires connect together measuring voltage at orange wire does not help, but switch on a zone then off again you should see or hear valve working and realise with one there is a delay turning off boiler.

 

[stem]

When either of the valves winds open, it triggers the microswitch and makes the orange wire in the lead from the motorised valve live. This wire is connected to the boiler / pump and starts the system running. When the valve closes the switch opens and the boiler goes off..... Unless of course the switch doesn't release, in which case it will stay on.

Someone competent with a multimeter would be able to test the orange wire/s from the valve/s when the fault was present and confirm. The tricky bit is that the orange wires from both valves are connected together, so would need to be separated for testing.

To confuse matters some (but not many) installers don't follow convention and wire it so that the grey wire from the switch is used instead of the orange. In which case the test would be with the grey wire instead of the orange.