Potterton Suprima L nightmare

[SuprimaHell]

Hello... Only now I've started to 'google' for solutions to my Suprima 80L boiler problems can I see why it's referred to as 'Suprima Hell'...

The boiler was installed in 2005 just before Regulations changed requiring Condensing boilers to be installed. It had the original PCB changed about 2 years ago to the newer Siemens design after a previous failure. That PCB had dry-joints and localised PCB heating evidence which wasn't solved by re-flowing the joints. No problems since until two weeks ago:

A couple of the radiators on the first floor weren't getting very warm, they were bled but there was no air, thermostatic valve fully open, return valve checked ok.

My plumber suggested the pump might be the problem and although dated 1998 I didn't think that was the case, but went along with replacement of newer Grundfoss with higher head/flow rating. He also throttled back the return valves on the two bathroom rads. which act as the by-pass circuit. These radiators stopped getting warm at all, and the boiler just didn't fire up. I opened the return valves some more and the pump sprang into life, indicating to me he'd shut them off too much.

Since then (but not necessarily related!), I've experienced the following:

Boiler demand from thermostat on, controller heating set to 'on 24 hours', red light on and relay clicks on controller, but boiler LED is flashing slowly with a yellow colour (not red, not green) and does not fire-up. No boiler clicking or attempt at ignition.

Pressing reset for short or extended time has no effect. Turning HW off or on has no effect. I have checked the time setting on the controller is correct (and AM when morning!). However, the boiler does spring in to life when you're not expecting it and the radiators and hot water do get hot.

I have changed the controller but that's not the problem. The system is wired as S-plan and is fully pumped with pressurised hot water system.

I'm reluctant to just rush out and buy another controller board due to cost where it might not be the problem.

Anybody else had the same problem and found out the problem?

Thanks in advance

 

[dominoman]

Does the boiler ever fire up.

I haven't seen the yellow light before, but maybe that's a newer PCB. Someone else here will maybe be able to advise on that.

If the light is slowly flashing green that means a call to heat, so if it doesn't fire then most likely it is the PCB again.

You could try testing the thermistor if you have a multimeter. It's easy to get to and just unclips. My problem, similar to yours, was fixed by replacing the thermistor. As soon as I removed it I could see it was burnt out

 

[SuprimaHell]

Does the boiler ever fire up.

I haven't seen the yellow light before, but maybe that's a newer PCB. Someone else here will maybe be able to advise on that.

If the light is slowly flashing green that means a call to heat, so if it doesn't fire then most likely it is the PCB again.

You could try testing the thermistor if you have a multimeter. It's easy to get to and just unclips. My problem, similar to yours, was fixed by replacing the thermistor. As soon as I removed it I could see it was burnt out

Thanks for the reply... The newer (Siemens) PCB has a tri-colour LED so it can be green or red, or with both red and green they make a yellowy colour, which isn't green or red!

The boiler does fire up, typically when it wants too (although within the expected timer/thermostat settings for time and temperature), and this gets the rads hot and heats water up but it's not consistent and the house doesn't hit target temperature. When the boiler has fired up the LED is steady green, at no time do I get a red LED.

I will access the PCB this evening and inspect the thermistor.

The various forums I have read do refer to the slow flashing 'yellow' LED being a call for heat status, so hopefully it is a dead thermistor. Can you advise what the cold junction resistance is expected to be? Actually, do you have the part code for the thermistor at all?

 

[dominoman]

This guide will show you the expected resistance:

http://gasboilerforums.com/thermistoreadingsC-P.html

I can't remember the part number but I paid around £11 for it new. If you check the manual it will have it

 

[SuprimaHell]

This guide will show you the expected resistance:

http://gasboilerforums.com/thermistoreadingsC-P.html

I can't remember the part number but I paid around £11 for it new. If you check the manual it will have it

Super... Part code is 404516 and it's an NTC thermistor with 1MOhm resistance at 25c and 73k Ohm at 82c.

Hopefully it's just this little beastie rather than the main PCB...

Anybody else similar experiences?

 

[Gasescape]

New style pcb flashing Amber !
New pcb time I'm afraid , it thinks the boiler stat is turned off.
Pretty common fault on the newer pcb's.
Probably find it's pretty random then gets progressively worse .

 

[SuprimaHell]

New style pcb flashing Amber !
New pcb time I'm afraid , it thinks the boiler stat is turned off.
Pretty common fault on the newer pcb's.
Probably find it's pretty random then gets progressively worse .

Hi Gasescape - are you referring to slow (approx. 5 seconds) amber/yellow flashing? Is this traceable to a dry-joint or particular component failure?

So much for the board re-design if it's again a common design fault.

How daft to put the PCB on the side of the boiler anyway - why not underneath at the coolest part of the installation.

 

[Agile]

Be aware that no DIYer should be opening the combustion chamber where the NTC sensor is fitted.

That should only be done by a gas reg engineer.

Nor should anyone be encouraging the OP to do "gas work" when he is not registered!

The sensors are very reliable indeed and rarely fail although many are replaced by those who cannot correctly diagnose faults.

Although when fitted they should be put in with thermal transfer paste and few RGIs seem to bother with thet.

Tony