Boiler constantly calling for heat CH & HW

[Bricks]

Any plumbers answer my question?
If boiler's constantly calling for heat for either central heating OR hot water (not turned on at same time) could that be cos of sludge in the heating system? Bath water is clear no sludge in that? My mate thinks it's sludge!

What controls the call for heat? Potterton suprima (not combi) boiler & Grundfos 15-50 130 Pump.

 

[Armo74]

Do you have any motorised valves? Could be a stuck valve or faulty microswitch.

 

[45yearsagasman]

Most likely to be a faulty external control or valve as stated. Do any of these look familiar? View media item 30391 View media item 38425

 

[Bricks]

Most likely to be a faulty external control or valve as stated. Do any of these look familiar? View media item 30391 View media item 38425

Yep! It has 3 ports coming from it. Slider underneath was in the middle, half way between min & max.

 

[Bricks]

Not sure what it's meant to be set at. Min or max.

 

[Armo74]

Could be a stuck valve. You need to isolate the electricity supply remove the silver box which will reveal a spindle try rotating the spindle left to right gently to see if it moves.

 

[Bricks]

Thanks. Will give that a try after dinner. My mates wrong its not sludge then?

 

[Bricks]

Correction. I need an eye test!!! That weren't min & max it were Auto & Manual with Open written underneath manual - just slid it to 'auto' & pump stopped as did the boiler??? Have I bu*****d it or solved it?

 

[45yearsagasman]

You've probably solved it. What caused the lever to stick is what I would be checking. It may well be the valve seizing.