Ariston 27 MFFI repeated lockout on DHW

[dresbo]

My Ariston boiler repeatedly locks out, lighting the ignition failure LED, but only when the heating is on. It's been fine all summer supplying hot water, but now it locks out 3-4 times a day. It will nearly always relight as soon as you press the reset button, although rarely I need to wait a couple of minutes before it will reset.

It appears relatively random. Sometimes it will run for hours, other times (usually first thing in the morning) it will only run for a couple of minutes. Typically from cold it will fire once and run up to temperature. Once at temperature, the flame will go out and it will continue to run with the temp reducing slowly. Then it will either refire, or, more usually, the red led will ping on.

Resetting will work, and then it will usually run for a bit before cutting out again in the same way. Once I've done this a few times it seems to run ok for a longer period?

I've drained and refilled it recently when I added an extra radiator and the water ran quite clean. Unfortunately I can't tell if it is related because I did that before turning the heating on this year.

Any ideas? I've spoken to a heating engineer, but he didn't seem confident that he'd be able to diagnose it, because it's intermittent, which wasn't reassuring.

It's definitely getting worse. It's gone from doing it once every couple of days to 4-5 times a day.

 

[adlplumbing]

looking at your other posts try bleeding your rads first and check your pressure gauge

 

[dresbo]

Thanks for replying.

I've bled them a couple of times - but I will retry that on every radiator jic. Pressure is stable at 1 bar and 1.5 once it's lit.

I replaced the autoair vent last winter as the seal failed. Could there be air trapped in the pump? Is it worth bleeding that? Would that cause it to overheat and light the LED?

 

[adlplumbing]

it can as water does not move quickly enought so it begins to boil
their are couple other posaibltys but they would need rgi

 

[dresbo]

I've bleed all the radiators and there's no air left in them.

It's still doing the same thing. It locks out more when the rooms are coming up to temperature (maybe just because it's on more), so it did it 4-5 times this morning alone. It always fires fine from cold, but it lights red when it's running without the flame and the water's hot.

Any more help please....I've got a new baby in the house and his mother isn't very pleased.

I've asked a plumber to come around, and I'll see what he says, but he didn't sound sure, so any hints of what to look at/test would be appreciated

Thanks

David

 

[adlplumbing]

ask him to check the flow temperture and the return tempertures

 

[dresbo]

Will do thanks.

I'll report back.

 

[dresbo]

Just to follow up.

After having a heating guy in who also didn't know, but suggested it might be the pcb (quite troublesome in this model apparently), I changed it.

Voila, it works fine now.

One note to anyone who does this - The new pcb (new model with removable eproms) sits slightly differently in the case and initially caused the reset button to be permanently pressed. I didn't notice this happen, but it has a strange effect, causing the boiler not to cut off the flame when it reaches temp. It keeps going until the safety cut-out hits at 80+ degrees and the power and fume lights start flashing. Adjusting the pcb slightly in the case (~1mm fixed this).