chaffoteaux MX2 30FF no flame detection?

[Paul]

our 4 year old boiler has started to intermittently give a no flame detection fault code. resetting the boiler usually cures it for a day or two. is this a common problem on these, and is it an easy fix.

[BigWallop]

If the boiler has a permanent pilot flame, then make sure it is not being blown out by the wind coming in the flue / chimney. This happened on ours, and was cured by a baffle on the outside flue pipe. Pop rivet a small sheet of galvanized steel around part of the flue to stop the wind from blowing straight inside.

If the boiler has an electronic ignition, then check all the electrical connections inside the boiler control panel. Vibration from running fans, temperature changes Etc. can cause the connector to loosen off from their mounts. The cold boiler will spark, but if it's hot it wont, sort of scenario.

It might just be getting old and starting to feel its age. Nothing lasts for ever, and the old bones will eventually have to give. If you're confident and competent enough to the testing your self, then go ahead and check all the things it could be. If you don't feel safe, or have any doubt about your ability to handle gas connections, then get someone qualified to check it for you.

I think all of us in the group, wish we could actually see exactly what posters are talking about in these situations. We could probably diagnose the problem in a couple of minutes, and fix it in a few hours on most of them. Ah well, it's not to be. :-)

Good luck with your fix.

[Jeff Layman]

We had a Worcester Bosch 3-year boiler exhibit a similar fault, except that after it was off for a while, it would work for an hour at most.

The PCB was changed, the FFD was changed, and the fan pressure sensor was changed without improvement, although after these were done the boiler worked long enough for the CH engineer to go to another job each time. The CH guy eventually found by sheer luck that there was a tiny split in the rubber hose from the fan unit to the pressure sensor. Of course, it was on the back of the hose, not visible from the front. Cutting 5 mm off the hose solved the fault and the boiler has worked perfectly since.

It seems that the split did not affect the working of a cold boiler, but once it had got up to temperature the split opened enough for the pressure sensor to assume that the fan wasn't working correctly.

[Paul]

thanks for the replies so far, the boiler has electronic ignition. i have checked all the connections and they look ok, the only thing i have noticed is that one of the wires going to the electrodes has a sooty deposit on it so there may be a short to the case, does the electronic ignition produce high enough voltages to arc through poor insulation?. looking at the wire the insulation looks ok

[BigWallop]

Yes. If the integrity of the insulation has been compromised, then the spark will not reach the tip and will jump to the closest negative point along its path. If you have an old BIC pen. Try sliding the case of the pen over the wire to create a shield where you think the short is occurring. An old plastic pop bottle can also be cut to make a wrapping for the insulation. Held in place with a couple of cable ties or something. Don't use metal ties as it will only give the arc another path to follow.

Where the ignition control wiring runs inside the boiler is not a hot part, as such, and should be cool enough for a thermal plastic, like the pen case or plastic bottle, to stay in a working condition for a good long while.

Good luck with your repair.

[geoff]

In message , Paul writes

does the pcb have a separate HT and flame sense lead ?

The sooty deposit will be because of electrostatic attraction around the HT - it's a red herring

Q1 has any wiring been changed recently which would lead to the possibility of live and neutral being arse about face

Q2 do you have bad earthing

Q3 is the sense electrode (if its not the same as the ign electrode) in the flame

Q4 If the HT lead is used for flame sensing, is it intact ? The fact that it will conduct a high voltage spark doesn't mean that it will conduct the small flame sensing current

Q5 do you have a chair to sit down on when they tell you the price of a new pcb?

[geoff]

In message , BigWallop writes

The problem is that it is not flame sensing, not that it isn't sparking at the electrode

You could maybe paint a Bic pen black with white ends and chant the magic words "izzy wizzy , lets get busy" while waving it furiously around, but other than that I really don't think it's going to help

[geoff]

But a split in a tube to the APS has nothing to do whatsoever with flame sensing

Not a similar fault at all

[Paul]

Yes

Ah ok

Nothing been touched at all, bolier been working fine for the past four years

Not That i am aware of, not touched any wiring recently

Will check on that, touch wood the boiler has worked ok since.

will check continuity and resistance of both.

Hopefully be ok on that, we pay a little extra on the house insurance to cover boiler breakdowns, we are covered for two hours labour and £100 + vat in parts, your going to tell me the boards £200 quid now. was hoping the boiler would pack up altogether before we called the insurance in, i know how hard finding intermitant faults is.

Paul.

[geoff]

In message , Paul writes

I'm sure that can be arranged ...

[Jeff Layman]

Perhaps I should have chosen my wording more carefully. Sometimes when a fault code appears, it may lead you in the wrong direction.

In my case, the WB showed a flashing lockout light. According to the fault-point diagram it was Fault E, and if the fault was not a gas supply problem, it could be rectified by replacing the spark electrode or HT leads, replacing the PCB, replacing the gas valve or cable, or replacing the flame sensor or cable. As previously stated, it was none of these. It should have shown as Fault B, with only the demand light on - that would have included replacing the APS tube.

[BigWallop]

I know a guy down the pub, who'll do it for a tenner. :-)

[geoff]

Which all goes to show that actually having a clue is better than following fault codes

If you recognised that your problem was "none of the above" why did you post it and call it a similar problem ?

It clearly wasn't