Glow-worm BBU50 problem

[brierley4life]

Hi there I was wondering if anybody could help. I have a Glow-worm BBU50 back boiler, the problem is it will not fire on it's own first thing, just goes on to the red light on the box under the fire, but once it fires it's ok all day till you shut the system down. I have had three gas engineers look at it, which between them, I have had a new gas valve, a new flue blockage safety device, a new thermostat ( not the room stat), a new thermo couple, new o rings for the flue safety device sensing tube and 4 serivces to no avail.
The first engineer wanted to fit a new combi boiler as the fix, surely this isn't the answer. So I got a second and third oppinion. The only thing I can think of is I had to have gas pipe to the boiler/fire repaired when the floor fitter knocked a nail through it, by the first gas engineer?
The system is a sealed system and the water pressure is about 1.3Bar, it's calling for heat, but will not fire, first time. It can take up to 10 minute to get it to fire but once fired it's fine. Shutting down and starting back up on demand.

 

[JimH]

You don's say if the engineers checked that the pilot light was close enough/striking the tip of the thermocouple correctly (0.5 inch)? Sounds like it may not be, especially if it runs all day after it finally starts - the chamber will retain heat after it's first run... that along with the a misaligned pilot may just be enough for the contacts of the thermocouple to make & open the gas valve allowing it to switch on & off all day when demand calls?
I'm sure the gas experts on this forum will be along shortly to advise you

 

[archiedale]

jimh, well said. thats the first check.

 

[Billy Bob Bob]

i take it it has a pcb??? would be looking at detection/ignition circuit ,jim h if its had a new oxy safe can rule this out mate unless pilot flame can be adjusted which is unlikely

 

[brierley4life]

Thanks for the replys. Through the bottom of the fire, you can see the pilot light touching the thermo couple. The pilot light fires straight up, it's part of the oxy sensing/ flue blockage device. Comes completely set up with thermo couple in place and electrode set to right distance.
Yes it does have a PCB, it's under the fire. It has a nice clean spark and the pilot light fires up straight away. The only two inputs, safety wise, I know of into the PCB is an overheat device and the thermostat. Which the thermostat has been replaced and the cutout has been tested, hopefully correctly.

 

[JimH]

i take it it has a pcb??? would be looking at detection/ignition circuit ,jim h if its had a new oxy safe can rule this out mate unless pilot flame can be adjusted which is unlikely

Hello gas man, you're absolutely right... the firing/ignition circuit board would normally be one of the primary suspects... but I discounted this - as surely at least one of the three engineers had to have checked it??? It doesn't leave anything other than the pilot light if they have confirmed that the board is functioning correctly... after all, the board does run perfectly well after it completes it's first cycle - indicating the fault is heat related?

 

[JimH]

Thanks for the replys. Through the bottom of the fire, you can see the pilot light touching the thermo couple. The pilot light fires straight up, it's part of the oxy sensing/ flue blockage device. Comes completely set up with thermo couple in place and electrode set to right distance.
Yes it does have a PCB, it's under the fire. It has a nice clean spark and the pilot light fires up straight away. The only two inputs, safety wise, I know of into the PCB is an overheat device and the thermostat. Which the thermostat has been replaced and the cutout has been tested, hopefully correctly.

Perhaps all the instrumentation including the board is working properly? Reading your posts again it would seem that the engineers obviously had concerns over the air flow into your chamber? The lambda sensor is working properly (replaced/checked by the engineers?), trapped gases within the chamber after shut down (poor airflow), must be a consideration - the sensor would not allow start up until clean air was drawn in?

 

[brierley4life]

Lambda sensor??? Only lambda sensor I know are fitted to vehicles. I thought somebody would know a common fault with the backboiler or a good engineer in the Barnsley area. I could call the engineer, he'd fit a part or turn some valve and I'd have heating on demand LOL. Looks like it's going to be that new heat system for chirstmas instead of the presents for the kids Bugger!

 

[JimH]

Lambda sensor??? Only lambda sensor I know are fitted to vehicles. I thought somebody would know a common fault with the backboiler or a good engineer in the Barnsley area. I could call the engineer, he'd fit a part or turn some valve and I'd have heating on demand LOL. Looks like it's going to be that new heat system for chirstmas instead of the presents for the kids Bugger!

LOL! O2 on the brain! Didn't even realise I had written that!