Gas Boiler wont re-light

TuppenceHapenny

This question concerns a Glow-worm Space Saver 50 MkII (Open Flue) boiler.

My gas boiler has been turned off for several months while I have done a repair to the central heating system and cleaned out the radiators. For good measure I have now refilled the system with water and cleaning fluid (Fernox F3 Cleaner). After refilling, I tried to re-light the boiler so I could turn on the central heating and let the cleaning fluid do its job. When trying to re-light, I can see the boiler sparking but the pilot light will not come on. Other gas appliances are working so the gas supply to the house is OK.

I have read on other forums that the problem is likely to be either the gas jet feeding the pilot light becoming choked with soot and tar and needing to be cleaned, or the flame sensor (thermocouple?) has developed a build-up and needs to be cleaned or replaced. Are these jobs easy enough to do myself (it seems to depend on how easy or hard it is to get at the pilot light)? Does the law allow me to attempt such jobs myself (without relevant qualifications)?

Also, is it sensible to leave the system filled with water and cleaning fluid while I try to get the boiler working, or should I re-drain the system to prevent further corrosion?

Gloomendoom

Have you tried lighting the pilot with a taper, rather than using the piezo igniter?

Alex1983

If it’s been off for a long period of time it will take a while to get the gas to purge the gas.

I would get it serviced and they will be able to clean and unblock the pilot if necessary, you could get a new thermocouple at the same time, they are very cheap and universal.

Ganga

Gloomendoom wrote: »

Have you tried lighting the pilot with a taper, rather than using the piezo igniter?

Our old Thorn Olympic was like that,you could push the electronic lighter till your thumb was sore or you could open the glass window and light it first time with a match.

TuppenceHapenny

Gloomendoom wrote: »

Have you tried lighting the pilot with a taper, rather than using the piezo igniter?

Thanks for the reply. I've had another look and I can't see a way of getting a taper in - it looks as if I would have to start dismantling the boiler to get any access to the pilot light.

TuppenceHapenny

Thanks for the reply.

Alex1983 wrote: »

If it’s been off for a long period of time it will take a while to get the gas to purge the gas.

I've tried pushing in the relevant knob for a few minutes before pressing the igniter but still not lighting.

Alex1983 wrote: »

I would get it serviced and they will be able to clean and unblock the pilot if necessary, you could get a new thermocouple at the same time, they are very cheap and universal.

I fear you are right - I will have to get someone in to repair/ service it. Do you know roughly how much I could expect to pay assuming it is just a case of doing a service and some relevant cleaning and replacing the thermocouple?

*j*

A faulty thermocouple wouldn't stop the pilot light from lighting. A faulty thermocouple would be indicated by the pilot light lighting correctly, but not staying on when you release the "light" button.

If the pilot light doesn't light at all, the two most likely faults are a lack of spark or a blocked pilot light jet.

It's an old, simple boiler. If it's been reliable for a while, don't let anyone talk you in to a fancy new "efficient" one without working out how long it would take to recoup the new boiler cost in gas price savings.

*j*

TuppenceHapenny wrote: »

Also, is it sensible to leave the system filled with water and cleaning fluid while I try to get the boiler working, or should I re-drain the system to prevent further corrosion?

Fernox don't say about their F3, but the similar Sentinel X400 cleaner says "Where systems are badly fouled, we recommend a longer circulation period (approximately 3-4 weeks). The product is not aggressive and can be safely left in the system for extended periods."

dggar

on a boiler that i had (Radiation FuelSaver 18 R) in the fault finding section there is mention of the Over Heat device.
Quoting from this:-


"If the overheat device has operated it must be reset by pressing the reset button at the centre of the device before the pilot can be re-established"


There could be something similar on your boiler.

*j*

I don't think that Glowworm Spacesaver is recent sufficiently recent to have an overheat cut-off, but here is a copy of the installation and servicing instructions, dated August '87....https://letsfixit.co.uk/wp-content/uploads/SPACE-SAVER-50-MKII.pdf

Pages 17 onwards have some fault finding charts.

TuppenceHapenny

*j* wrote: »

A faulty thermocouple wouldn't stop the pilot light from lighting. A faulty thermocouple would be indicated by the pilot light lighting correctly, but not staying on when you release the "light" button.

If the pilot light doesn't light at all, the two most likely faults are a lack of spark or a blocked pilot light jet.

Thanks for the information - that seems to confirm it is likely to be a blocked pilot light jet (since I can see it sparking). Am I correct in thinking I am not allowed to clean it myself as I do not have the relevant gas qualification?