Potterton Kinfisher MF Floorstanding 80,000 Boiler

[achurch]

My ch boiler only seems to be cutting in when hot water is requied,I had to turn my HW cylinder stat right up to 80 to get the rads to get hot, I noticed earlier in the day when I hit plus 1 hour for heating on the main central heating control that even though the amber light illuminated on the panel the green boiler light did not fire up and the rads did not get hot as normal only warm I suspect that once the hw in the tank gets up to the temp on hw stat I the rads will go warm, normally within 15 mins the downstairs rads are all hot any advice would be appreciated.My system is well due for a service the boiler is around 9 years old, the actual rads and pipework much older
Any help would be appreciated Thanks

 

[Tibbot]

Your boiler & pump are working, the fault is with your controls. These are the symptoms of a failed mid-position motorised valve powerhead. Do you have a 3 port mid-pos valve?

 

[achurch]

Thanks for replying Yes I do its a silver box landis & staefa with a slider with open or manual it is currently in the open position, if it is this is there any way to test it ? Thankyou

 

[kevplumb]

lock it mid position (man)

do rads warm up

 

[Tibbot]

Yes I do its a silver box landis & staefa with a slider with open or manual it is currently in the open position, if it is this is there any way to test it ? Thankyou

Fault causing it to work only off the cyl stat, which means even if it passes through both CH & HW sides, it'll shut boiler & pump when HW satisfied. You can test that 240V leaves your r/stat on CH demand.

A new powerhead usually cures it.

 

[achurch]

When you say lock it in mid postion is this man position,My wife had chucked some cloths on it I suspect they have moved the slider what postion should this be in for normal use ? ive pushed slider upwards to man position it can go down to a ledge then be pushed round to open position thankyou do you think that this is still faulty do I need whole valve or just part?

 

[Tibbot]

do you think that this is still faulty do I need whole valve or just part?

I've stated the valve's faulty twice because I believe it's in perfect working order.

The powerhead is only part and not the whole valve. (Assuming yours is a removable type).