Baxi Barcelona issues

[rick]

Baxi Barcelona, under service contract - in May this year started giving intermittent ?explosive ignition? ? when it happens gives a seriously loud bang This boiler had been upgraded to 100HE spec some years gao.

Multiple visits and loads of parts ? fault just got worse ? was also now failing to ignite and going into Lock out .. every couple of days. Another load of parts ? including upgrading the burner door so new style

1 piece electrode assembly could be fitted. (and replaced several times)

After multiple no -improvement visits ? one engineer found electrodes shorting to Air Box door panel ? I supplied him with high temp sleeving ?. Stopped shorting but still locking out.

After about a dozen visits one Tech noticed that every time it failed to ignite he could see a flash over on back of ignition board ? multiple board changes, individually and as a pair with control board. Lockout frequency increased to every start cycle ? so boiler 100% down for 1 week.

Another Tech found that the harness to the transformer had been badly burnt (burner box seal leak ?) .. and all insulation burnt off harness ? replaced transformer & harness. Could be as a result of all the work rather than root cause.

After lot of investigation ? Tech found electrode wires had been interchanged (presumably during one of many electrode changes) ? causing wrong direction of spark ? and maybe damage to cct boards. Baxi really should have non-interchangeable plugs on these leads to prevent such a mix up.

Today again another Tech visit ? another pair of cct boards and ignition board harness, still the same ?. Intermittently boiler fails to ignite on first strike and as you hear each ?click? of attempt you can see a flash over on rear of ignition PCB ? in area to rear of where electrode connects.

My assumption is electrode failing to arc ? the energy is built up and has to dissipate somewhere ? and flashes over on back of board.

This flash over may be the cause of damaging the boards ? or the effect of an already damaged boards.

List of parts so far ?

Initial fault ? Explosive ignition New burner box door seal New style ceramic burner New electrodes (twice) New flame sensor New electrode harness New ignition board >Increased to ? also intermittent lock out New burner box door to allow new style electrodes (folded edge type) New electrodes (new longer style) New flame sensor New condensate trap (new style) Replaced heat exchanger Replaced flow thermistor Replaced Ignition board cct board (twice) Replaced Control cct board

Increased to 100% lock-out every start (flash over) Replaced flow thermostat Replaced Ignition board cct board (twice) Replaced Control cct board Replaced ignition transformer Replaced ignition harness Replaced main harness

>Back to ? explosive ignition (flash over) Replaced Ignition board cct board Replaced Control cct board Replaced ignition harness >Fault free for 6 weeks

Back to explosive ignition (flash over) Replaced Ignition board cct board Replaced Control cct board Replaced ignition harness

So significant cost of 10 circuit boards, complete heat exchanger, burner, burner door upgrade ? still ongoing.

Has had 23 Tech visits, 9 different individuals, and more than 60 Hrs on site.

Anybody experienced such a fault ? thought I would ask as this is dragging on for so long, about the only items not changed are gas valve and fan.

[Tim+]

Many moons ago we had and Ideal condensing boiler that started lighting explosively. Turned out to be a faulty gas valve that was letting gas into the combustion chamber before the "pilot igniter" had lit. This boiler had a two stage gas valve, the first stage admitting gas to an electronically lit pilot and then the second stage is supposed to only open once a flame has been detected in the pilot light.

Does your boiler have a similar system? I suspect that they've all moved over to "single stage" ignition of the main burner but you never know...

Tim

[rick]

Single stage I think ... no pilot flame ... just straight electrode for ignition along with a flame failure detector.

I asked same Q ... on DIYnot forum ........ and have 2 guys who state this is an obvious fault, simply fixed - known top all (except the 9 Gas Safe Techs who have been to my place presumably) but they are not prepared to tell me what it is - even though I will not be touching gas myslef.

[Tim+]

Ah, tossers. Dontcha just luv 'em? ;-)

Getting back to your boiler one would imagine that it would have a "purge" phase following a failed ignition to prevent enough gas building up to cause an explosive ignition. Still makes me wonder if your gas valve is bypassing gas slightly resulting in gas build up in the combustion chamber before the next ignition sequence.

It does sound though as if there must be another fault too to explain the ignition failures.

Tim

[Tim+]

On further reflection, it may be the the gas valve as well as leaking slightly isn't passing enough gas when it's supposed to be open to get the gas mixture right for ignition. All in all I would have thought a replacement valve was the obvious next step.

(I should add I'm not a gas fitter, just interested in how things work, or ought to work).

Tim

[harry]

Yes faulty gas valve could cause problems. Normally, gas accumulations in the boiler are flushed away in the pre-purge part of the cycle. So it would have to be a big leak.

Gas explosions can be caused if there is too much air/insufficient gas in the mixture. So partially blocked gas jet can cause this problem. Usually just wire brushed and poked clear with a bit of wire. May not be apparent during normal operation if boiler is oversized (quite common)

[charles]

I had a similar sounding problem on my, then, 25 year old, boiler. It was due to the overhest thermostat failing.

[Tim+]

I could see that causing inappropriate lock-out but explosive ignition.

Tim

[rick]

That was my thought ... not enough gas so it fails initial 'strike' then there is too much gas in there for when it does light - hence the bang .... but no proof of that.

[Mark]

What is the number of red led lockout flashes you are getting is the gas valve modulating correctly when it is working

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[rick]

Most of time - it does not lock out, just explosive ignition ......... when the lock out issue was happening (2 months ago) It was safety lock out ... Red LED flashing aprox once per second.

[Tim+]

I'm sticking with gas valve issues. ;-)

Tim

[rick]

I'll let you know how it goes :-)

[Mark]

if you have had the updated pcb board fitted was the yellow jumper removed you get a number of led flashes then a 1sec pause which then repeats to give an indication to what is causing the lockout also in my experience that boiler need to run with the temp knob setting no more then 1/3 on

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[rick]

Took a look at the card ( ans 2 spares) jumpers 1, 3 & 4 are fitted (4=yellow)

Not sure why you would want to lower temp ?......... I have an underfloor heating system, the manufacturers advice was to run boiler at maximum temp. So when store call for heat - boiler will work at maximum efficiency ... they advise running at lower temp will reduce efficiency.

[Tim+]

I think they're talking bollocks. If you have underfloor heating you have a huge radiating surface and consequently you should be able to heat your house with a lower system temperature. (Imagine having just having one radiator to heat the whole house. It would have to be f*cking hot! The more radiators you have the lower the system temperature can be.)

In theory boilers work more efficiently at lower temperatures due to greater heat recovery from condensation. The lower the temperature of the return flow the greater the heat recovery from the flue gasses.

So it seems you have incompetent repair men and an incompetent manufacturer. Maybe this explains some of your problems? ;-)

Tim

[rick]

Why then would you have a 'hot setting' if it makes no sense .... just wondering. It has been on max setting for 12 years. (maybe wrongly)

On the comment "you should be able to heat your house with a lower system temperature." yes .. but the more heat I store in Thermal store ... i.e. the battery, the more the low temp loop for UFH can run for before boiler needs to call for boiler input again.

Fewer high efficient burns are better than multiple burns.

[Tim+]

If you have a conventional "under-radiatored" house, you may need a higher boiler temp to achieve satisfactory heating. With new condensing boilers systems though it's normal to fit bigger radiators and run the system at a lower temperature for increased efficiency. The same boiler may be used in either situation. Hence the temperature control.

Ah, didn't know that you had a thermal store but I'm not sure that affects the argument. How much difference it makes in practice I don't know.

Tim