worcester bosch heatslave 16/19 won't reset

[destroyit]

the burner lockout has tripped on my above boiler, and initially would reset and the system would run for a few minutes, giving me some central heating or some hot water, both seemed to work fine. Now it trips out after a few seconds and won't reset unless i switch the machine off for a short period of time first. If i don't switch the whole thing off, pressing the reset on the burner does nothing and the amber light remains lit - well it clicks but the light does not go out. i have tried to run the boiler with the burner cover removed and i've checked the photocell which is definitely not black. Does anyone have any further suggestions i could try, as i have a bit of time on my hands before my usual boiler service people re-open in the morning - it would be nice to have some heat tonight (living in a granite build house near a river in a dip - kinda chilly here!), and by the looks of some of the useful posts/replies i've seen on other threads, this seems the best place to ask right now!!

 

[Burnerman]

If the lock out light won't go off, I guess a new control box is needed......its usual to wait a minute or two before the thing will reset, though.
John

 

[destroyit]

are you saying then that it is most likely the fault starts and ends with the control box and isn't stemming from something else that caused it to go off first? Actually i've just tried it again hence editing my reply... something that struck me from earlier, i've turned off the demand for CH and just turned on the HW, to heat up the heatslave? and so far it's not locking out. I had wondered if there was a problem with the pressure in the CH as that is going up and down like a yo-yo, (leaking somewhere? Bleed screw doing overtime? whatever, i've had to refill it a tiny bit a couple of times as i remember that low pressure in CH isn't liked by the boiler somehow... though yes i see that still it doesn't affect it being a faulty control box - so the CH is not on, and the boiler isn't locking out. I've no idea what pressure the CH should be, hot, or cold. It's on 3 bars, cold, and yes i guess that is high, but can you make a mental connection for me between the CH not being at the right pressure and if maybe my misuse of it is agitating the control box? Hot water still heating up right now...

 

[destroyit]

i spoke to soon (and the boiler obviously heard me typing?)

 

[Burnerman]

First things first, really.....3 bar of pressure in your c/h system is too high - I'm surprised that the prv hasn't lifted by now. I'd reduce the pressure by letting water out of a radiator bleed valve - it takes a while but it will work.
Usually a pressure of 1 bar or so is fine to start with - this will rise a bit with the c/h on - up to 1.4 bar or so. If the pressure is bouncing about a bit then the expansion vessel needs to be repressurised. This is around 10 psi of air with the c/h system depressurised.
None of the above usually leads to burner lockout though, and if it was mine I'd seriously think about a new control box.
John

 

[destroyit]

well the enigneer came out today, and the diagnosis of faulty control box sounds most likely (and the engineer said otherwise but i was not so convinced by what he had to say). He reckons the PRV was faulty, and was leaking. Not sure what this has to do with burner lockout. I mentioned what you said about the expansion tank affecting the pressure guage and he paused and modified his story to... the expansion tank was overpressurised and blew out the PRV, then he checked the expansion tank pressure, and added some more pressure (air?) to it. Boiler seemed to work for about twenty minutes, on first the DHW only, then on CH only. All looked good. He booked an hour on his job sheet, then hung around for a bit to see if it would go to lockout again, which it did... "need a new oil pump" he said. Then said something about the photoreceptor taking too long to twig the burner was fired up. So i need a new PRV (but not essential he says) and a new oil pump (but can use the boiler for 20 mins at a time, with the front burner housing removed, and restart it when the appliance has cooled down), and i probably need a new expansion tank, and he's not too happy with the photoreceptor, and that may as well be replaced. Do you think he actually knows what is wrong with my boiler? The company as a whole are very good, and he is a pleasant enough, polite young lad, but I feel i need to ask them to provide a second opinion from another engineer as I don't feel certain he really knows the cause of it wishing to stay on lockout, and control box still gets my vote somehow. I can see the link between me not looking after the CH properly and keeping it overpressurised, causing expansion tank to work overtime and blow PRV, but he seems to think the oil pump did that? He says it locks out when pump gets hot. Should I ask the company to give me a second opinion from another of their engineers, or does his diagnosis sound correct? Would be grateful for someone's opinion on that... sorry for such a longwinded post!

 

[Burnerman]

Seems like a garbled bit of spherical objects, really.....
If the PRV is leaking, there would be water visible in the overflow pipe outside. This would cause the pressure on the gauge to drop - eventually to zero.
Too much air pressure in the EV wouldn't blow off the PRV unless it was ridiculously high. The only way to check these is to depressurise the system, and then add air to around 10 psi as a starter. If the EV is working then the pressure would rise, with the C/H on, about 1/2 a bar on the gauge. With the C/H off, the presure falls again to around 1 bar.
The photocell (PEC) which he calls the photoreceptor? looks at the burner flame once lit, and if it sees light it keeps the oil supply on and the flame burning. If it can't see light, the burner shuts down and locks out.
As for the oil pump causing the EV to work overtime...yeah, right
If the burner locks out when it gets hot, then the solenoid coil on the oil pump is the immediate suspect as they do fail in this way.
Call someone else, mate.
John

 

[destroyit]

ah - he did say something about the solonoid failing... can this be replaced or is that why he is saying the pump needs replacing? Is it an all in one, or can you get just the solonoid coil bit? Sounds like i probably should get another engineer out as you seem to know quite clearly what you are saying, (unlike the lad who came here earlier) which is great, thanks.

 

[Burnerman]

The solenoid coil sits on the top or side of the oil pump, and it allows the oil to pass to the nozzle when the control box tells it to....this is usually about 8 sec after switch on (the motor and fan spin during this time to purge the flue with fresh air).
The coils are available separately - quite expensive for what they are though - and are simple to fit.
Often coils start to break down when the burner gets warm, causing a lock out after a certain time.
You do need someone else to diagnose your problem, I fear....guesswork only gets you so far.
John

 

[destroyit]

ok i tried the thing again now, the day after... yes bang on 8 seconds, then the boiler fired up, and cut off about 2-3 seconds later. sound solonoidy still?

 

[Burnerman]

From this distance, I'd be considering a photocell fault.....it can't see light so assumes that the boiler hasn't lit up, and closes it down.
Your guy has called it the photoreceptor.
John