Poxy Potterton boiler again...

During the winter I had a lot of problems with my Potterton Suprima going into lockout, which was resolved with a new PCB (thanks Geoff!). Now it is only doing water heating, it has started locking out again, but we don't notice now until we run out of hot water :-(
What happens now is that the red LED is flashing, so I reset it. It starts the fan, then you hear the spark (sparks a number of time, which the old PCB apparently didn't), but it does not ignite. It will then try again, and usually succeeds on the second attempt.
So, any ideas on what the problem could be? Even if I have to end up calling in an engineer, I'd like to be pre-armed with some info.
On a related subject, the boiler is in my new downstairs cloakroom on the wall above the short soil stack. The stack has been boxed in, with the boxing continued up to the ceiling, so that it also covers the side of the boiler. As this interferes with the boiler cover and will need to be cut away to allow service access, I am thinking of building a cupboard around the boiler. Are there any regs to do with this? Any advice on how much space to leave around, ventilation, etc?
Thanks.
Regards,
Colin Swan Nildram Operations
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I have a Suprima as well (had not seen the rude comments on the group when I bought it!), and have found that the spark gap is quite critical. The gap is also the flame detector device, and I suspect that if it is too wide the board decides that there is no flame, and tries ign again. After three unsuccessful tries it goes into lockout.
Have a look in the manual and set the spark gap at just over the minimum specified - this cured a similar problem on mine.
I haven't got the manual to hand at present, but could dig it out if you do not have yours available.
PS, beware of the ceramic insulator while adjusting electrode spacing.
I would be interested to know if this works for you, as I suspect some of the lockout problem is down to gap spacing, among other factors no doubt......
Charles F
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On Thu, 03 Jul 2003 11:03:39 GMT, snipped-for-privacy@nilnospamdram.net (Colin Swan) wrote:

winter. I realise you replaced the PCB, but maybe the refurb isn't perfect? I've solved, for the time being, my problems by going over all the main joints on the PCB with a soldering iron. Some of them were too close to risk tho.
And I've also enclosed mine in a kitchin unit. Made sure to drill plenty of holes above and below. Seems OK like this. Apart from that cutting out of course! Good luck
regards
-Rob
Oh and for the programmers and pedants: </metoo>
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Not perfect ?
No Suprima (or other) boards go out of my factory if they are not working properly.
This board has been working for some time now, and the problem seems to be that either there is a problem with the pilot valve, delivery of spark to the electrode or flame sensing - which can be due to a number of factors

--
geoff

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Dive dive dive...
--
*Why is the word abbreviation so long?

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Dunno about clearance, but ventilation wise............Building Regs document J, Part 3 "Additional Provisions for gas burning appliances with a rated input up to 70kW (net)", diagram 3.2 specifies one opening at top & one at the bottom, each 1000mm2 per kW input (net) - that would be ~ 12cm x 12cm for 50,000Btu rated balanced flue boiler.
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"David H." wrote:

50kBtu/hr (net) = 14.7kW so you are correct about the vent sizes.
However please note that almost all modern boilers require no additional ventilation. Many can be installed in kitchencupboard with a little as 5mm clearance. The part J regs apply in the absence of instructions to the contrary. Also require 75mm clearance all round to combustible surfaces.
Note the vent sizes would be halved for ventilation direct to outside air.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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I hope it's not the pcb ...
Can you see it sparking in the combustion chamber? It might be sparking somewhere else
Is the pilot igniting? If so, there's a high value resistor which, if gone wouldn't allow the pcb to sense the flame
If not, it sounds like the valve isn't working. Check that there are (about 110V DC (can't remember offhand)) volts on the pilot valve contacts. If there are and the valve's not opening, you have a faulty valve, otherwise, I'll be expecting a phone call from you. If the pcb does not sense the flame within a certain time (13-15 sparks) the boiler goes into lockout.
If you still have problems, give me a ring (01923 229224)

--
geoff

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writes
SNIP

I've just had two intermittent failure to sense flame problems on different boilers: One was simply a loose auxiliary earth wire on the burner which then sometimes completed the circuit via the boiler metalwork and occasionally didn't. The other was on a housewarmer back boiler and the end of the ignition/sense electrode lead had corroded off within the porcelain mount. The spark could jump the gap but the sense current couldn't In both cases of curse the pilot did light but the boiler didn't think it had and so went into shutdown.

Check your installation and service instructions which "might" say you don't need purpose designed ventilation but if they dont then yes you most definitely do and the sizing is remarkably large when you look into it for older boilers (based on the boiler input rating)
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