Odd Suprima behaviour

[Johnandlin]

We've had the PCB changed some months ago following "lock out".
Worked great for a while, now a new problem.

In the morning from cold, water/heating comes on via timer, pump starts, boiler fires up and within 2 minutes goes to rest. Green light is flashing for about 2 minutes then the whole thing shuts down(solid red light) pump stops. Within seconds it fires up again, pump starts, the boiler fires up (solid green light) within a minute it goes to green flashing, runs for a couple of minutes then red light and pump stops. Then again and again.
After about 20 minutes the feedpipe to the hot water cylinder is only luke warm as are the radiators.
After about 25 minutes, suddenly the thing seems to fix itself and then the boiler stays alight, the pump keeps going and for the rest of the day we are ok. We've got BG 3*, but they dont come when the system is cold. By the time they arrive system is working ok. They are coming again this week, but don't seem to have much of a clue what they are looking for, can anybody here help please?
Thanks

 

[stardanny]

It may be a faulty PCB? Loose connector to PCB?

 

[Johnandlin]

It may be a faulty PCB? Loose connector to PCB?

Not answering my own question but - Could it be that as the boiler warms up the connections on the PCB improve as a result of heat expansion?

 

[stardanny]

It could be it, but you say it was working ok for a few months. Boiler was working ok for rest of day. Do it keep happening every day?

I would think it is PCB.

Make sure the system is full by checking F&e tank.

Other would try to answer your question.

 

[superdupergasman]

leave the system switched off the day that they are coming so it is cold!

I had one do the very same last week, initially I thought thermistor, changed that but still faulty, replaced PCB under warranty and problem was solved.

 

[Johnandlin]

Yes it happens every morning, but ok for rest of day after first 20-25 minutes.

CAnt leave it off until they arrive, too cold and they only promise to arrive sometime between 1 and 6pm

 

[Corgigrouch]

With all due respect, if the boiler only plays up when it is cold, then how is the poor guy going to diagnose the fault if it is hot?? Sooner or later the fault will develop until the off mode is permanent...This is usually on the coldest day of the year and everyone is too busy to attend to you

 

[Johnandlin]

For the gasman I managed to keep the system cool and it turned off when only luke warm , turned back on again etc
Gas man said he thinks its the thermistor, didnt have one but is coming back tomorrow to fix.

Hopefully that will do it

 

[snb]

Have had this problem a few times with various suprimas and has turned out to be the gas valve on it's way out. They usually last about 3 months before they die completely

 

[frankthegasman]

the prob could be the gas valve as they have had a problem when the pcb goes wrong it messes up the electrics in the gas valve have a look at BBC WATCHDOG potterton suprima you might get a supprise.

 

[Soggy_weetabix]

Gas Valve. Change it.

David

 

[Johnandlin]

the prob could be the gas valve as they have had a problem when the pcb goes wrong it messes up the electrics in the gas valve have a look at BBC WATCHDOG potterton suprima you might get a supprise.

Gasman didnt arrive today he's coming tomorrow.
When I search BBC Watchdog potterton suprima there are just 2 pages and no list of faults. Am I looking in the wrong place?

 

[corgiman]

the only fault watchdog picked up on was the printed circuit board

you'll have no joy with any others

 

[Johnandlin]

Gas Valve. Change it.

David

Well, BG changed the Thermistor, which seemed to fix things for a while until this week with the return of the cold weather. We're back to boiler firing up, going to rest after 2 or 3 minutes, then pump stopping. Then the whole thing reigniting, couple of minutes later going to rest, stopping starting again.
This means the water in the rads goes from waming up to cold, to warming up to mildly warm, and takes about 2 hours to get anywhere near hot.

I have BG 5 star cover (or whatever it is called these days), but they have been out 4 times and dont seem to be able to fix it. If the next step is the gas valve any ideas how much to replace please? Should I try to convince BG that it needs replacing or saould I find a local expert??

 

[superdupergasman]

Homecare 200 is the new name....

Just let them come and see with the system cold.

When its doing its thing you need to be checking voltage to the gas valve to propely diagnose it....might still be the PCB.