Heating Pump Continuous

Syerston_HQ

I have a Potterton Suprima boiler with a mains pressure hot water tank and the central heating pump in the airing cupboard runs almost continuously. Every couple of minutes it stops for 2 or 3 seconds. When the pump stops and starts the boiler clicks. The boiler also comes on for about half a minute fairly frequently during the night even though hot water and heating are off at the timer. The PCB has been replaced. Any ideas as to what else needs replacing? Thanks.

albyota

found this on another forum....thankyou Joseph Mackintosh

The Suprima is very sensitive to water flow and will lockout very quickly if the pump fails or if the motorised valve is shut. The programmer/Timer controls the motorised valve and the boiler should not come on if the pump is not powered.
If the boiler is switched ON after a long time of being OFF (1 hour say) and it does startup for a while, touch the pump body after a few minutes to check how hot it is. It should be cool to the touch. If it is very hot, the pump is shot and shoild be replaced.
These are the other checks you should make:
Remove the cover of the boiler - On the heating flow pipe quite high on the left hand side of the boiler, is located the overheat stat and the casting sensor above it. The overheat stat will cut power to boiler if it has tripped and the casting sensor may just cause the boiler to lockout. Quite often, people replace the PCB when the real fault is the casting sensor.
The casting sensor reports the temparature of the heating pipe to PCB. If the sensor is faulty and reports the the pipe is hotter than it is, the boiler may pull the plug and force the boiler to go into lockout. This is a safety feature to ensure the water does not become dangerously hot.
Testing The Casting Sensor:
Make sure all power to boiler is switched OFF.
If you have a multimeter, you can test the casting sensor by setting the meter to the 20KOhm range or higher and place the probes across the sensor terminals. The expected reading should be around 14KOhms at normal room temparature..

Really both the casting sensor and overstat should be changed together.

Potterton have recently been criticised on Watchdog for their poor PCBs. Give them a call on 08706 060780. They are currently sorting out the lockout problem for free. If nothing else you should try and reclaim the money you spent on the replacement board.

Syerston_HQ

Thanks but I'm not sure it's relevant as the boiler doesn't lock out. Heating and hot water work fine, problems are pump running continuously and boiler coming on frequently for short periods.

Syerston_HQ

Frost stat calling is logical but I haven't got one. At least no mention in boiler manual and none externally as far as I'm aware.

bobmedley

We had the same & the Sunvic motorised valve was shot - it was supplying 240v to the pump continuously.

Worth checking.

bambibashercol

thats where i would be looking first, the 2 port or 3 port valves

calebdylan

be sure that the boiler is properly earthed before touching the metal body its a safety advice because shorted pumps can have high level voltage and current levels which will cause harm

albyota

calebdylan wrote: »

be sure that the boiler is properly earthed before touching the metal body its a safety advice because shorted pumps can have high level voltage and current levels which will cause harm

OR.....

Possibule a shedloadybold of falollopping spondulickies, oh deep folly
and series in the thoughts now for better time... never was than now.
Not to menshy-menshy then uglymode unearthy boiler, but who carelodes if tickly sparkus and giggly all chortly in the chestyfold, but not digressy very dangerlode and causey the visitate to the hospitole
And there would be general consternail uproar and complaint about the dangerlode, all the lectrickery and floaty around the houseloader.

AB’s Tribbly To Sir Stanley Unwin (Sorely Misty in the Worldlode) (for Cardew)

mcgillm

I had a similar problem, timer on my boiler would move to off but boiler would continue to run (pump in the airing cupboard also). tracked it down to the following;

The boiler switches on at the wall through the timer.

The boiler is then running by either the thermostat switching it on (temp control) and/or the hot water pump running - essentially like two swtiches.

In my case when the timer went to swtich it off the switch that controls the pump was stuck and therefore continued to run, this meant that the boiler (even though the control was switched off) remained on and running...

May need to check the switch that controls the pump - in my case it was some WD40 and playing with the manual override that fixed the problem - once resolved the switch was playing ball with the boiler controls....

albyota

Syerston_HQ wrote: »

Thanks but I'm not sure it's relevant as the boiler doesn't lock out. Heating and hot water work fine, problems are pump running continuously and boiler coming on frequently for short periods.

Did you manage to get it fixed?

Syerston_HQ

The problem(s) aren't sorted. Not sure what to do. The white valve at the back I have seen working, not the one at the front. Can I test these? If so how? Tried to post a photo but no luck. This link might work, take the space out from after the first h.

h ttp://i636.photobucket.com/albums/uu84/martinbhtbf/PICT1946.jpg