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Andrew Smith
Andrew Smith, Engineer
Category: UK Plumbing
Satisfied Customers: 3627
Experience:  Domestic Gas, Commercial Gas, LPG, Unvented Hot Water, Part P Electrical, Commercial Catering
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I've just read a series of post regarding saunier duval

Customer Question

Hello. I've just read a series of post regarding saunier duval sd30e combi where the boiler flails to stay on. My fault seem to be intermittent as well. No problem with pressures etc, new DHW thermistor fitted and most connectors cleaned. The flame sometiems comes on and then off every few minutes but doesn't locks out. Randomly it also fails to ignote and locks out after sparked for 5 - 6 seconds. Then it could be okay for 2-3 days...
I have noticed tho that voltage to the gas valve is variable betwee 4 to 29v across black and white and jumps from null to 94v across red and blue
Any advice?
Submitted: 1 year ago.
Category: UK Plumbing
Expert:  Andrew Smith replied 1 year ago.
Will the boiler still try and light with the main cover off?
Customer: replied 1 year ago.
Yes it will every time
Expert:  Andrew Smith replied 1 year ago.
Ok, sounds like a gas/air mixture problem or the flue. Can you check the flue seals, especially the one on the top oif the boiler
Customer: replied 1 year ago.
Which seals do you mean Andy? I have just noticed there is no seal between flue colector and fan - shuld there be obe?I'm struggling a little bit now as it didn't fault since yesterday and voltage to gas valves across both sets was constantly at around 27v and 93v... Why would it stop jumping up and down?
Expert:  Andrew Smith replied 1 year ago.
There is a jubilee clip at the back where the fan connects - make sure it is still intact.
Take off the hoses and clean the metal hose connections to make sure they are clear.
Ensure the flue outside is clear and not overgrown.
Come back to me in the morning when you have checked these items.
Customer: replied 1 year ago.
AndyJust stripped the fan down and could bot see any jubilee clips - the fan is just pushed into flue ducting with use of metal sleeve. I have attached some photos of ducting itself. There was a small amount of loose soil like substance in the ducting and this wased cleaned.I also disconnected the APS, cleand rubber tubes and connectos on it. Just haave a look at attached photos...
Expert:  Andrew Smith replied 1 year ago.
ok, as long as it is a good tight fit.Now it is clean, is it working any better?Make sure you WD40 your fan as it can make it run faster and smoother.
Customer: replied 1 year ago.
Hard to say if it's better as it's still locking out when turn hot water first time in the morning but comes on after I reset it. It went to lockout twice today but it's been okay since I reset it few hours ago.I greased the fan up with wd40 but the fan is only 3 months old so shouldn't be a problem.Anything else I should check?
Expert:  Andrew Smith replied 1 year ago.
Something sounds like it is sticking, perhaps why it doesn't work first thing in the morning.Are you able to check power to the gas valve and just make sure it gets power as soon as the ignition starts clicking
Customer: replied 1 year ago.
I'll test it for power in the morning Andy.Today its been locking out few times, even after it was operating okay for few minutes. The only change is that voltage to gas valve is inconsistent across red and blue and forever changing - see attached video. It was constant over last few days until today
Customer: replied 1 year ago.
For some reason I cannot attach it, just type in 'gas valve sd30e' on youtube please

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