Intermittent boiler problem

[steve-m]

Given all the dire warnings about DIY boiler repairs I am rather loathe to raise the subject in case I am shot down in flames. But let me just say that I do know when I need to call in the experts and am quite happy to do so.

My query concerns a Myson Orion Fanfare boiler new in 1992.

Intermittently the main burner will fail to fire up. Often the scenario is that the boiler will fire up fine from cold, run for a while, then if it shuts down for any reasons and then the system call for heat again the boiler fails to fire up. The pilot light lights up with a good sized flame, I have just fitted a new spark ignition electrode, but the main burner fails to fire up. The fan, the pressure switch, the thermostats are all working fine and I have replaced these items over the years.
When the main boiler does fire up there is a full electrical feed measurable at the main burner gas valve contact, but when it fails to fire up, despite the pilot lighting up OK, there is no electric measurable at the main burner gas valve contact.

This indicates to me that it may be due to a faulty ignition circuit PCB. I do not mind whether I replace it or I get someone in, it is just they are expensive items and it would be nice to know if I have correctly pin pointed the problem. The more so as being an intermittent fault chances are that if I get someone in the boiler will decide to work fine on that occasion.

Any thoughts on this one?

Regards Steve

 

[corgiman]

i would think more liekly to be a faulty air flow swtich not proving the fan sparodically rather than the ignition pcb

you are breaking the law and shouldnt do, i can only hope you are not a muppet and are competent as if you arent then you are endangering those you wish to enjoy the warmth in your home

goodluck

 

[steve-m]

you are breaking the law and shouldnt do,

Only a court can decide if someone has broken the law, you can advise people of the law and refer to case history but it is up to a court to decide.

The gas regs state
For all property, the Regulations require that:


- all work to gas appliances and fittings shall be carried out by a competent and suitably qualified engineer who is CORGI (Council for Registered Gas Installers) registered

In the main my email referred to testing the boiler and trying to identify faults. That is not work to a boiler it is testing of the boiler, quite a different thing. Everybody tests their boiler everyday by turning it on and seeing if the water gets hot, if you delve a little deeper is that contravening the regs? only a court can decide.
When does work on a central heating system become work on a gas appliance? again only a court can decide. If I change the motorised valve in the system is that work on a gas appliance? After all it has a direct effect on the operation of the boiler even if it is separately located. If i change the spark electrode on the boiler again is that work on a gas appliance or work on ancillary equipment to the gas appliance? again only a court could decide.
I suspect that the law would only consider taking action if you actually undertook work on the gas side of the appliance, breaking and making joints in gas pipes or altering flues etc.

Anyway, so far I am only testing the system and that does not seem to be against the law.

Regards Steve

 

[chrishutt]

With regard to the legal position (Gas Safety (I&U) Regs 1998), only a competent person may work on gas fittings. Unless you are doing that work by way of trade (being paid) you (or your employer) do not need to be Corgi registered.

Gas fittings are defined as gas pipework, valves, fittings, apparatus and appliances. Work is defined as including maintaining and servicing an appliance. Competence is not defined.

In effect, you can work on a gas appliance within the limits of your competence. As long as you don't make a major mistake it would be difficult to argue that you had exceeded your competence.

 

[geoff@cetltd]

i would think more liekly to be a faulty air flow swtich not proving the fan sparodically rather than the ignition pcb

I think you're wrong there

The pcb will not get to igniting the pilot if the APS is faulty


you are breaking the law and shouldnt do,

wrong again

 

[Soggy_weetabix]

a good size pilot flame?

Pilot flame picure not explained.

What effect does burner have on pilot light when fully lit?

Fan operating at full speed throughout?

Rectification probe, aps and least of all PCB may be faulty.

CORGI territory (sic) to be honest.

Ill do my thick DIY bit and say "it may be your thermocoupling effecting your thermostack".

Dave

 

[geoff@cetltd]

The important question is whether the spark stops when the pilot lights

if it does, then the pcb is sensing the flame, and its a relay not operating on the pcb or the main gas valve (I cant remember if you said you had tested that)

if not then it's the pcb, the HT lead broken, the electrode not in the flame or bad earthing

It can't be a thermocouple - it doesn't use one