Potterton Kingfisher mf - overflowing into expansion tank

[mk2phil]

Hi there,

On the weekend I noticed that there was water coming out of the expansion overflow pipe in the loft. The boiler was dumping hot water out of the expansion pipe into the tank. Turned the temperature control down on the boiler and it didn't happen again all weekend.

Then this morning the CH & HW came on as normal, but after an hour or so the red light came on to indicate a boiler lock out - had to reset to start boiler again. Boiler starts up, so then I slowly turn the temperature knob down to see if it would turn off. Managed to get it all the way round to the off position without it turning the boiler off.

System is 'C' plan (Gravity HW, pumped CH). Radiators are all getting hot (hotter than normal actually) and all bled. Pump bled too.

So, my assumption is that the temperature sensor is playing up?

Any help much appreciated

 

[Agile]

I dont agree with your assumption.

You should first check the pump with a "finger test" ( see FAQ ).

If thats OK then expect its sludge problems. That may have become obvious from the coulour of the water from the pump and in the F&E tank.

Tony

 

[mk2phil]

I've had to drain it down many times in the last year or so due to decorating, upgrading rads/pipework etc. Doesn't seem to have any problems when draining - i.e water retention that might be caused by sludge. Admittedly the water is light brown when drained but I'm assuming this is normal.

The system also heats quickly and evenly - if sludge were an issue wouldn't I be noticing poorly performing rads?

System is not old either - was all replaced around 6-7 years ago.

Not disagreeing, just trying to provide as much info as possible.

Thanks for your help

 

[Agile]

Did it pump over on CH+ HW or HW ?

Thats either caused by a faulty pump or a blockage.

If you have fiddled with the temperature sensor and removed it then you will have to refit it with thermal transfer paste otherwise it will overheat.

Its unlikely to have actually failed but you can measure the resistance cold.

The water can be a light straw colour but not really brown. That may well have resulted during the pumping over. That can sludge up a system in hours and cause rads to pinhole within days.

Can you take and post a picture of the pipewhere the vent and feed

Tony

 

[mk2phil]

I will try and take a picture when I get home.

Thinking about it, sludge in the pipes wouldn't explain why the temperature control on the boiler failed to turn off the boiler when I turned it all the way down before actually turning it off..? Would it?

 

[Agile]

Not obviously but that control is not a direct stat and relies on the reading of the sensor which will be giving a false reading if it has been removed without refitting correctly.

Tony

 

[mk2phil]

I haven't touched the sensor yet, it was just the first thing I'm planning to change.

I should say that 2 weeks ago I upgraded from a single panel radiator in our living room to a double panel type. Cant see that this is connected in any way but thought I'd mention it...!

Can I get the thermal transfer paste from your average plumbing shop?

*EDIT*

I've just remembered, in the early hours of the morning of the first day the boiler overpumped, there was a loud bang noise. After this, you could hear water moving around in the pipes. Sounded as though a large bit of air had moved and the system was filling/moving around accordingly. Boiler was off and neither the HW or CH was being called for.

Not sure if that could be connected or just a coincidence? As I had refilled the system a few weeks earlier due to a rad upgrade I had assumed that this was the last bit of air escaping from the system?