Boiler cuts out but pump continues to run.

[P.HOLLIS]

Please can someone advise, I have a Potterton Suprima 60 it lights up and gets hot but then it cuts out but the water pump keeps running, the Boiler will intermitantly start up but after a short while it stops again with the pump still running. The boiler shows a constant red light (not tripped) and a flashing green which I believe means calling for heat. I have tried a screwdriver in the pump method (its a Grundfos ups 15-60) and I stop it from rotating, do you think that the pump might be failing and that the boiler then reaches its temp and cuts out? Any advice? Thanks

 

[keekster64]

I've had a similar problem. I found that in some boilers the pump is supposed to run on after the boiler has switched off until it drops below a preset temp. If it continues to carry on after this you may have a problem. Mine has a potentially faulty thermostat causing the problem.

 

[corgiman]

Please can someone advise, I have a Potterton Suprima 60 it lights up and gets hot but then it cuts out but the water pump keeps running, the Boiler will intermitantly start up but after a short while it stops again with the pump still running. The boiler shows a constant red light (not tripped) and a flashing green which I believe means calling for heat. I have tried a screwdriver in the pump method (its a Grundfos ups 15-60) and I stop it from rotating, do you think that the pump might be failing and that the boiler then reaches its temp and cuts out? Any advice? Thanks

It will if you keep sticking a screwdriver in it while its running

You only ever do that to free the pump up if it is sticking
The Suprima has Pump over run and will run for a a lenght of time, how long depends on its factory setting, after the burner drops put

this is a fuel saving thing and stops the boiler cycling on and off.

the green light flashing does mean that the external controls are calling but the boiler stat may be satisfied and thats why the boiler does not fire.

My advice is that if you turn off the programmer and stats and the pump still runs you have a problem (either the 3 port valve is stuck, unlikely or you need a PCB)

I would recommend that you dont stuff any more screwdrivers in to a running pump though

 

[P.HOLLIS]

Thanks for the replies, do you think that it may be the Boiler thermostat thats playing up and if so how do I check if it is.

 

[P.HOLLIS]

Sorry I forgot to say that I have turned off the programmer and the pump shuts down, also when I turn the power back on the boiler fires up for a few moments and then cuts out.

 

[corgiman]

I f the pump shuts off when the programmer is off what is the problem??

is the boiler locking out

as for checking the stat my Opinion is that checking it aint a DIY job get Potterton/Baxi Out

 

[P.HOLLIS]

The problem is that the boiler is'nt heating up the hw/ch, its not locking out(red light flashing) it just will not stay on for long periods. I have had the normal problem of lock out with this boiler but this seems to be different or is it? :

 

[COG]

just read your texts and it does sound as if the boiler is reaching temp before the system has ,if it was a sticking diverter i would assume you would have lost only one circuit CH or DHW if you have lost both i would suspect a slow pump it should be eft on sped three to run but you can switch it to speed one and the shaft should rotate too quick to follow with the eye , if you can follow it around then its running too slow on speed one so probable too slow when on three,mind you sticking a screwdriver in it to stop it wont have helped. changing an integral pump should really be left to a Corgi eng.

 

[P.HOLLIS]

Thanks for all your comments so far, I have ordered a new pcb and am hoping to install this in the next day or so. I think that I may have two problems on the go and sorting out the pcb may at least sort one and if I'm lucky both, do you think that a faulty pcb could also be showing up as a Boiler temp o/h?. The pump is not in the boiler its a standard Grundfoss (I was shown the screwdriver routine by a plumber that I called out in my last house) I will update once the new pcb is installed.

 

[corgiman]

you probably were shown the screwdriver thing when the pump is not running mate Please dont do it while it is running as you can damage it

 

[Registered Gas Man]

I have ordered a new pcb and am hoping to install this in the next day or so.

Tinkering can go too far!!!!!

Take this advice..............

my Opinion is that checking it aint a DIY job

Sounds like standard pump overrun to me

 

[flashbang]

You have the same boiler as me. Mine will run the pump after the boiler switches off, by design.. It's to prevent too much heat build up in the heat exchanger. The Potterton should power the pump from an output on the boiler itself. I.E the pump should NOT be connected to the junction box, but directly to the boiler. One of the advantages of this boiler, is that it will run the pump once every 24 hours, even if the heating and hot water are not called for, to prevent the pump from sticking during spells of inactivity.. Brilliant feature.. Providing, of course, that the power is left on!

My boiler will also cycle on and off for some time before the room thermostat is satisfied. I have no idea if this should happen, but I suppose it makes sense. Just because the water is hot enough to trip the boiler stat, doesn't mean the house is warm enough yet. It always gets there eventually though.
I don't think you have a problem at all, but you might want to check the pump is wired to where it should be, it's clearly marked on the boiler electrical input.
Cut the power, before removing cover, just in case!!!
Good luck.
Flashbang.

 

[P.HOLLIS]

OK this is an update, I have now installed a reconditioned PCB and so far (24 hrs) all seems to be going well. The Boiler is staying on longer and heating at a far higher temp than it was, it is also not tripping in and out which is what its been doing for some months. At this moment in time it would seem that the PCB not only gives you the tripping problem but also other problems like the boiler o/h light coming on and off even when its not on long enough to get hot.
Flashbang, maybe u should look at your boiler and see if this continuous switching is a prelude to PCB failure. The PCB cost me £50 all in so not to bad on the pocket if it is indeed the cure. Thanks again for all the advice to all who contributed.

 

[flashbang]

P.Hollis, thanks for the info. My boiler has done the on/off switching since day one, and I suspect this is normal until the house reaches desired temp.
My lock out problem was cured by resoldering the PCB, but just in case you're right, where did you get the PCB for £50..... The best price I've seen quoted on this forum was about £75. and that was for a repaired board. (Which was not recommended)
Thanks in advance.
Flashbang.

 

[r2wtrials]

see my problem with the suprima 30...
same question as above.. where did you get the pcb for £50? need one myself..