Long Time To Ignition

[tan159753]

I need some advice here as I don't know know if this is a problem or if it is acceptable performance.

From cold, the timer switches on, the boiler goes through its quick check, flue fan kicks in and the pilot sparks all as normal. Now comes the problem. It is taking at least 4 minutes of sparking for the Pilot to ignite sometimes much longer. As soon as the Pilot eventually lights, the main burner fires up almost straight away and radiators heat up as normal. After this, the pilot only takes a second or two light.

The problem seems to be getting worse in the last few days taking longer and longer for the pilot to light.

I don't remember it taking so long before. The spark seems fairly bright as usual. I would have thought any spark + gas = ignition. The gap the spark jumps is about 12mm.

Questions.
a) Is this spark gap enough?
b) How strong does the spark have to be?
c) Is this normal or perfectly acceptable to let the boiler spark away for so long?.

I don't want to sound paranoid but with small children (2 of which are unwell) and cold weather, I want to avoid a breakdown and keep the heating downtime to a minimum.

I have a Potterton Prima 80F Boiler about 14 years old, in an open vented system is it helps.

 

[Agile]

Modern boilers mostly have a spark gap of 4 mm ( £1 coin thickness ).

However, I expect some older boilers might have been a little more but 12 mm sounds way too wide.

Of more concern is that, unless you are competent to work on gas, you should not be opening the combustion chamber and the usual advice would be to call a CORGI !

Tony

 

[tan159753]

I can clearly see the ignition rod and the grounding terminal through that the spark jumps across too through the small window. I do not need to open the combustion chamber.

Even though 12mm seems a lot, the spark seems happy enough to jump across in regular repetition. Well when I say seems happy, i'm only asssuming it is but have not stopped to ask it as it doesn't hang around very long

Anyway, called an engineer this morning and he has just been to see the boiler. Says there is a lot rubbish on the electrode and grounding terminal so he just cleaned it. It does seem to ignite faster (1st or second time round rather than the previous 4 -5 times) when hot. The real test to see if its fixed will be in the morning when the systems cold.

 

[Agile]

I would not expect to be able to measure the spark gap size by looking through a small viewing window.

If the gap is smaller then the spark disapates more energy on that 4 mm and gets hotter rather than a long 12 mm where the energy per mm is only a third.

What did the engineer say about the length of the gap?

Tony

 

[tan159753]

Sorry, it does look bigger through the window. I wasn't here when the engineer arrived but my brother was. Speaking to him now he says it was definitely more than 4mm but less than 12mm. More like 6 or 7mm.

Does anyone know how long it should take for the boiler to fire up initially? It still is taking about 1 minute from cold but is fine when hot. Is that OK or is there problems lurking?

 

[Agile]

It will not really matter much.

However in proper condition it should light up either immediately or within the first three sparks.

The pilot jet assembly probably needs cleaning or replacing and possibly adjusting but thats fiddly and not many people will do it now ( apart from the old school BG engineers who have mostly retired by now ).

I do though!

Tony