Baxi 100 HE Plus - Lockout

soram · 13-11-2015 8:07pm #1

OK before I start I've read the BAXI is mega crap and problematic but I can't afford a new one at the moment!

Secondly - I'm not looking for a technical solution here so please don't jump on me immediately with the RGI thing!

I've had this one 10 years and it's never really been reliable but we nursed it along. It's had a lot of bits changed and generally worked unless it didn't spark and then just had to be reset to go again.

Now I have a different problem - sort of. I have three zones. One is downstairs and run with a NEST thermostat. One is upstairs and all rads are on TRVs and the third is the cylinder on a thermostat.

Over the Summer the the upstairs zone is never used and turned off. I know I had an issue last year with the upstairs zone but ignored it as it was coming to Summer...Now it's Winter......The downstairs zone works perfectly - 99% of the time. It turns on normally, heats up and turns off again. If I turn on the upstairs zone, however, it turns on and I can hear the fan modulate as it heats up. After 40 minutes or so the regulator shuts the boiler down internally with the green light still on as I assume the TRVs are now closed up. After 2-3 minutes the boiler checks again if heat is needed; I can hear the pump come on and then the fan but it does not spark. When it sparks the clicks are loud and obvious and it is like it is not attempting to spark. After 2 minutes it lights Ignition Lockout. I need to press and hold the reset button for at least a minute to get this reset and generally the same happens again. If I leave it for an hour or so and come back it will generally now spark and start properly. If I leave the TRVd zone off it generally works fine and will restart day in day out. The issue though is reproducible.

Water pressure is good and in the green, the flow switch was replaced recently as was the pcb......these were for other reasons but neither had an effect on this problem.

Hence my recourse to the experts here! Reading old posts on this boiler it seemed like a right mess and I don't want a Young Scientist project made of it.

If anybody reading the problem description could recommend somebody in the trade that would be confident in dealing with this and could PM me I would be much appreciative!

Cheers

soram · 13-11-2015 8:14pm

Sorry - forgot to say I'm in South County Dublin!

K.Flyer · 13-11-2015 9:59pm

soram wrote: »

I have three zones. One is downstairs and run with a NEST thermostat. One is upstairs and all rads are on TRVs and the third is the cylinder on a thermostat.
I know I had an issue last year with the upstairs zone but ignored it as it was coming to Summer...Now it's Winter......
The downstairs zone works perfectly - 99% of the time. It turns on normally, heats up and turns off again.
If I turn on the upstairs zone, however, it turns on and I can hear the fan modulate as it heats up. After 40 minutes or so the regulator shuts the boiler down internally with the green light still on as I assume the TRVs are now closed up.
If I leave the TRVd zone off it generally works fine and will restart day in day out. The issue though is reproducible.

Does the boiler work perfectly fine on the Downstairs and Hot Water zones, either together or separately, without the Upstairs Zone being on ?
Does the problem only occur when the Upstairs Zone is activated with either, both or none of the other zones on or off?
Do the upstairs radiators heat up to a reasonable degree before the boiler shuts down?

Have you checked that the thermostat for upstairs is operating correctly. Checked that all the TRVs upstairs are fully open and that the pins in the valves are moving freely. If they are all good, I would be checking the wiring from the zone valve next and checking that the zone valve itself is opening fully when activated. Also check for any isolation valves on that part of the system, ensure that they are fully open.

soram · 13-11-2015 11:07pm

Many thanks for your answer.

To me it looks like when the downstairs zone is on the thermostat generally turns the boiler off before it has to itself and it can restart from that seemingly. But when the TRV zone is on it shuts down itself but cannot restart until some time/temperature later.

Guessing I'm thinking myself into a a new pcb again but still need somebody to do it for me and would prefer if it could be confirmed

K.Flyer · 14-11-2015 1:09pm

From how you have described it I doubt it is your pcb. The pcb controls the boiler and is dependent on the information sent to it.
You say everything operates fine until you bring in the upstairs zone, which would imply that there is either a wiring conflict or a circulation issue.
How are the individual zones controlled, are they separate pumps or motorised zone valves.

soram · 14-11-2015 2:08pm

Hi - maybe I wasn't too clear. The upstairs zone heats fine when turned on first but as it's on TRVs eventually the flow gets restricted and the boiler ramps down. Circulation is restricted but the boiler should cope with that by recognising the water is too hot and so shutting down. After a while I believe it tests the water temperature again and if it is cold now it fires up - my boiler does not fire up at this stage. I can hear the pump and the fan but there is no click as would be normal. It seems it is not trying to even spark. After 2 mins or so it locks out. If I try to reset it there and then I need to hold the reset button for an age. The longer I wait (hours!) the shorter I have to press the reset for....mostly but not every time it will then start and click and fire up again

Problem is if it locks out during the night it's damn cold in the morning......

I think, but am not sure, that it might do the same on the normal NEST controlled zone. When working this zone I think the NEST normally cuts off the boiler before the boiler itself makes the decision that the water is too hot. I suppose I could turn off all the rads and prove it! Maybe I'll try that later..

soram · 25-11-2015 11:58am

FYI - Turned out to be the PCB in the end

Baxi 100 HE Plus - Lockout

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