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.