Chaffoteaux & Maury Minima MX2 24 FF - ignition lead iss

[Stephen19]

The boiler had been cutting out on heating and had the green 70 & 80 lights flashing. The engineer yesterday switched over the following two leads. The ignition lead and the flame sensor lead. By switching these leads over (a very simple fix) the thing worked.
Apparently one lead needs to be more sensitive than the other so the switch over put the less sensitive lead (or one with a slight fault) onto the less intensive demanding job and therefore works properly.
Does this all make sense and will it be a long term fix? I understand that new leads are not expensive and can be attached later on easily if required. But for now, it all works. I am after advice on these leads and the fix please.
Thanks
Stephen

 

[Agile]

It sounds as if the ignition lead insulation may have been damaged and was sparking to chassis.

Changing the leads can be considered as a permanent fix if I have guessed right.

Why are so doubting of your engineer's advice?

Tony

 

[Stephen19]

Why are so doubting of your engineer's advice?

Tony

Thanks Tony, I am not really doubting it as it all worked, I'm just wanting to learn a little about the fix and of if its for longer term success. It seemed strange to me though, that you can simply switch the two leads over from one job to another and its fixed. For instance, if a lead is not workking on one job, why would it work on the other? But it does! the answer must be in the sensitivity levels of the two jobs varying a little so the slightly faulty lead can still achieve success with the lower level sensing.
Thanks

 

[Agile]

No, not at all, if its what I expect!

The ignition signal is at about 13,000 volts and will produce a spark in air about 7 mm long!

The insulation on the wire is only about 1 mm thick but has a higher dialectric strength than air so it can easily contain the 13 kV.

If the insulation gets squashed or damaged it can allow a spark through that part.

However, the flame detection voltage is less than 100v and that is easily contained within the insulation even if its badly damaged.

Many of the people fixing boilers are not very good at explaining these things even though they understand it well.

Tony

 

[Stephen19]

No, not at all, if its what I expect!

Many of the people fixing boilers are not very good at explaining these things even though they understand it well.
Tony

Thanks again Agile, all explained and summed up nicely for me and I am very pleased the fix sounds a long lasting one!