Halstead db 50 gas cutsout

[Rusty Bullet]

I have re-posted this because what I said last time was inaccurate.

My dad has a three and a half year old gas boiler (Halstead Best db 50 a.k.a. Wickes LW50ci). He has spent a lot of money on engineer call-outs but has yet to overcome the problem.

Today we did some simple testing.

We started the boiler and then deliberately shut the gas off. The flame in the gas chamber went out immediately. About six or seven seconds later, the Ignition Lockout Device (ILD) come on. This is as expected. We then turned the gas back on.

From cold, the boiler worked for an hour or two. Whilst out the room, the boiler switched off and the ILD light came on.

We put the central heating thermostat (CH) to max, reset the ILD, and sat and watched.

After a few minutes we heard what sounds like a switch or relay clicking off and the flame went out. This was despite the room temperature had not reached the level that the thermostat was set at. After a couple of seconds the gas re-ignited, however as soon as the flame detector started to glow, the system tripped as the ILD light came on.

This now happens repeatedly. The gas will cut out after about a couple of minutes and the ILD will ‘trip’ a few seconds later.

Could anyone possibly suggest what might be the fault, or where we might start looking?

We have tried using a ‘spare’ ILD and it does the same thing. However, the ‘spare’ ILD’s history is unknown. The ILD is a Honeywell S4565CF.

Many thanks in advance.

 

[ChrisR]

Well if it only does whatever it does when ON for the hot water and not the heatong, or vv, it's the fault of the external controls perhaps. Could be that the contacts on the relevant thermostat are dirty so the signal to the boiler goes rapidly on/off. I would expect the boiler to then switch off for several minutes but not lock out, unless its overwhelmed!

I'd get a live wire to the Switched Live input to the boiler and try to simulate the fault. You'd latch open a motorised valve if you have 2 x 2 port ones so the water has somewhere to go.

Those ignition modules are a bit odd. After a lockout the thing won't reset unless there's a call for heat AND the temp knob is turned up! Try it on max.

 

[Rusty Bullet]

Thanks for the reply, what I didn't make clear is that it does it for hot water AND Central heating.

After the initial hour or two of good operation, it starts to play up. When it starts to go wrong it will keep going wrong every couple of minutes, vis runs for a minute or two then the gas goes out, fires backup again, then the Ignition Lockout Device (ILD) trips. It's as though power is removed from the gas pump (one can hear a click from the gas pump/ ILD). The ILD then takes 5 or so seconds to 'react' then trips out. It looks as though the gas valve is powered via the ILD.

I do suspect the ILD, but it is odd that another ILD (second hand and history unknown) does the same thing.

Best regards

 

[ChrisR]

INtermittent cut-outs and the like are very often a result of the fan operating near the switch pont of its pressure sensitive switch. Which usually comes about because of lack of servicing of the appliance - which should include cleaning the fan. Air Pressure Switches aren't the most reliable components either.
A common check which you might observe WHEN you get a corgi regd engineer to look at it, is to get the boiler to its not-happy situation then undo the case a bit to let some air in. This improves the air flow and proves the point. YOU aren't allowed to undo the case.

 

[Rusty Bullet]

Thanks for your last mail, I'll pass your thoughts on to my father. We certainly wouldn't attempt anything ourselves that is risky. I will find-out about the servicing history.

I am asking these questions because we have already spent money on engineer time but it is still broke. We are therefore trying to get an idea of what is wrong.

It seems clear to me that the lockout is due to no gas, it's the reason the gas cuts that's a mystery to us. The other problem is that we cannot guarantee that it will go wrong if a repair man turns up.

Would the points you have made cause the gas to cut-out? I can hear a relay type 'click' when the gas cuts.

Best regards

 

[ChrisR]

Yes it would. You're hearing the solenoid in the gas valve, closing. Which is what happens if the fan proving switch thinks it isn't getting enough pressure. The last thing it would do would be to turn the gass off to make the boiler safe. Same thing if it overheated, say.
I don't think you'll risk a lot by loosening the case a bit for diagnostic purposes as long as you don't leave it like that.