Potterton Suprima 80L lockout

[bertscrog]

Hi All. I’m an appliance engineer not a gas fitter however I hope someone is able (and willing!) to help/advise.

I have a Potterton Suprima 80L boiler which is suffering from intermittent lockout. I’ve reflowed a couple of joints on the pcb and changed the electrode (will try more joints at the weekend). Boiler is in a small, purpose built brick shed on back of extension, alpong with a frost stat.

When I push ‘reset’ the fan starts up, I can hear the relay buzzing then clunking, a faint sparking then either ignite or drop out, as it pleases. It has fired up first time or after, say, third ‘reset’, no obvious pattern.

It was put in 2 years ago to replace a smaller Glowworm and obviously the pipework was amended to suit the additional rads (heating has never seemed 100% since though perfectly usable. Don't think it was balanced correctly, if at all!).

It’s weird but it seems to regularly ignite automatically for the afternoon/evening but the mornings I’m having to go out and reset it. I did suspect the cold but this morning (Thursday) it was actually milder than yesterday (Wednesday) afternoon here.
Other half seems to think it also always comes on when she switches Prog to ‘on’.

There is a Potterton EP2002 programmer, a 3 port mid-position valve (new - replaced by me earlier this year-different prob-solved), a cylinder with Drayton cylinder stat, a pump with pipe-work running up and down, 11 rads, 3 towel rails.

If anyone has any suggestions (keep em polite!), I’d be grateful.
Cheers.
Regards,

Gary.

 

[gazthepottertonengineer]

you need pcb kit part number 5111603

 

[bertscrog]

Hi gaz.

Yep, thanks for that.

I suspect the pcb hence the resoldering as it's a darn sight less expensive than a new one!

So you reckon my (boiler's) symptoms point to the pcb for sure?

Cheers.

All the best.

 

[gazthepottertonengineer]

yes it does sound like the spark generator on the pcb is knackered bite the bullet get the pcb you can get them fairly cheap on E-bay and they come with full instructions how to fit them

 

[bertscrog]

Hi All.

- UPDATE -

This afternoon's setting went in to lockout!

On going out to check I can actually see the spark every time of its 8 attempts!

Possible gas prob?

It kicked in when I thumped the bottom of the boiler a few times quickly though probably coincidence.

 

[bertscrog]

Hi again.

I had to reset it this morning, not particularly cold. Put it on permanent 'on' as we got up late!

I went out a short while ago (boiler been fine since I reset and put 'on') and with boiler at rest I put meter across the gas valve. As it opened it fluctated between 217V and 219V. I believe this should be 300V. Will this make that much of a difference? Valve not open fully because of this? Maybe why needs a few attempts so that gas builds up?

Does this make sense to any one?

Cheers.

 

[Trev B]

Had a similar prob with a glow worm compact combi, every time I took out the solonoids out on the gas valve,(completely rubber seatings the lot), and re fitted them the damn thing worked for a few days and then reverted back, got in touch with manufacturers and they said pcb. (also had low voltage which is what made me suspect pcb) Changed that, no difference, changed the gas valve problem solved, must have been a weak solonoid or a sticky valve seat.
Be careful with the pcb as the more you mess the more likely you are to stuff something up there may not be anything wrong with, and if you do try what I did be VERY carefull and test the parts well with leak detector to be sure of no leaks. I'm a corgi registered gas installer so maybe a little more experienced than yourself.

Have you tested the voltage at the solonoid when boiler does fire and when it does'nt ??If the voltages are the same it points toward the gas valve.

Hope this helps, Regards, Trev.....

 

[ChrisR]

Bert as you obviously have a digi meter test the reistance of the gas valve coils.
There are 5 pins, one coil is on I think 1 and 2 and the other on 4 and 5. You should get about 1400 and 2800 ohms.
The waveform applied to the gas valve isn't a sine wave or straight DC (iirc) so you get odd values depending on your meter.

 

[damorad]

My experience?
I suffered daily resets (flashing red light), no hot water or heating. I removed the motherboard and re-soldered all the main joints, especially the sockets that the off board sensors connect to (I could see hairline cracks around the base of the pins).
That was weeks ago, its been running sweet ever since....

£15 for that soldering iron was a sound investment

Regards
damorad

 

[bertscrog]

Hi again.

Whilst dormant the voltage across the gas valve was zero but as the prog kicked in the pcb sent 217V - 219V dc to the valve. I was expecting 300V dc as per manual. Is this confirmation of anything? Maybe not enough oomph to open valve fully?

It's worse now as it has to be set manually morning and evening.

Gonna try a blanket solder at the weekend (being very careful, Trev! )
I'll test for ohmic value if that don't work.

Cheers all.

 

[gstens baxi]

The gas valve is ac.

 

[bathjobby]

And its mains voltage so no idea why you are expecting 300V !

 

[bertscrog]

Chaps, I know mains is ac.

I was expecting 300V DCcos that's what the manual says the reading should be!

 

[bertscrog]

Hi to anyone still interested (lol)

I am definitely getting around 220V DC across the red and black to the gas valve; 478V AC! Honest!!

The ohmic values of the valve solenoids are approx 1350 and 2800 (very similar to that suggested by ChrisR.

Saturday morning, tried a few more joints (though none seem too bad at all) stopped igniting completely last night so I'm obviously needing to make a decision.

Was bidding for a pcb on ebay but got beat by a 'lurker' at the last minute yesterday (couldn't compete, it closed whilst I was on the road). Oh well. I notice there are a few 'Buy it now' for between £115 and £130. Has anyone bought one of these off ebay and it been exactly that described?

Sorry to seem so tight as to not just get an engineer in, just haven't got the money to say "Do whatever it takes".

All the best, all.

 

[Softus]

Hi to anyone still interested (lol)

I am definitely getting around 220V DC across the red and black to the gas valve; 478V AC! Honest!!

Interested? Yes. Astounded? Utterly. I don't see how you're getting both DC and AC at the gas valve solenoid.

Is it possible that your meter is (a) overreading the 478VAC, and (b) reading some kind of damped RMS value when set to DC? A good meter will filter out AC when set to DC, but I have no idea how good yours is.

The ohmic values of the valve solenoids are approx 1350 and 2800 (very similar to that suggested by ChrisR.

This would suggest that the solenoid isn't faulty, although they can break down under load, in which case the unloaded resistance values are misleading.

Saturday morning, tried a few more joints (though none seem too bad at all) stopped igniting completely last night so I'm obviously needing to make a decision.

Was bidding for a pcb on ebay but got beat by a 'lurker' at the last minute yesterday (couldn't compete, it closed whilst I was on the road). Oh well. I notice there are a few 'Buy it now' for between £115 and £130. Has anyone bought one of these off ebay and it been exactly that described?

Sorry to seem so tight as to not just get an engineer in, just haven't got the money to say "Do whatever it takes".

The last time I had this quandary, I bought the PCB and it made all the difference - this was with a Puma80, a cousin of the Suprima80 and one that suffered from the same hideous build standard for PCBs.

It's your decision, in the end, but if you should be able to find the part at a very good price on this forum somewhere...