HRM Wallstar boiler burner lockout

Hello oil experts,

I've just moved into a house with a wallstar boiler which locks out once the central heating system gets up to temperature. It's always had annual services and its last one was two months ago. The entire burner unit was replaced about a year ago.

The engineer today can't figure out what's wrong with it, and admittedly it's old and may need replacing, but before I do that I wanted some advice from some other experts.

Some details:
- the central heating is a vented system, hasn't been power-flushed in some years apparently.
- there doesn't appear to be air in the system
- when the central heating comes on in the morning the boiler fires up and runs perfectly to heat the whole house up.
- once the whole system is hot the boiler stops firing, as expected
- once the system water temperature drops the boiler fires to start the cycle again and usually at this point (or on the next cycle) it will cut out after only a few seconds of burning, requiring a manual reset of the burner (outside)
- resetting while the system is hot results in a fairly quick repeat lockout
- the lockout light on the boiler (inside) never lights
- the overheat switch on the boiler (inside) never gets tripped
- the burner is clean, oil line is clean, no air bubbles, etc. burner side looks good

The engineer admitted it was a bit of a mystery and suggested replacing the elderly heating pump and doing a power flush, because perhaps the water speed is not fast enough through the boiler and the overheat is tripping out.

What I don't understand is the burner only locks out when the system is hot. It runs happily for quite some time before it gets to this state. If it's an overheat, why does the boiler temperature overheat itself not kick in?

I'm happy to get a new boiler if that's what's required, but if anyone has any suggestions or experience I would be happy to hear them!

Thanks,
Chris

To add - the boiler successfully runs and lights each time, running for a few seconds quite happily, before suddenly cutting out and going to lockout.

Has your oil engineer checked the solenoid on the oil pump. From cold they can run until warm and then break down. Quite common on gas boilers too.
Jeff

jeff the gasman said:

Has your oil engineer checked the solenoid on the oil pump. From cold they can run until warm and then break down. Quite common on gas boilers too.
Jeff

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Hi Jeff, thanks for the suggestion! I think he figured that since the boiler fires up and burns it wasn't an oil-side issue. Wouldn't there be some time between the oil supply to the burner stopping and the lockout happening? The lockout is immediate and the burning stops at the same time as the fan and everything else goes out.

Solenoid is a common fault on these

eaton said:

Solenoid is a common fault on these

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If it's the solenoid that would mean no oil getting to the burner, is that correct?

The burner starts up no problem at all and burns quite happily for a few seconds before the whole things stops. Lockout doesn't work this way usually, right? Wouldn't it take a second or so before it shut things down?

Get yourself a "REAL" engineer if the burner Locks out OF COURSE it is oil related!!!!!!! pillock!!

Your pillock would do well by looking at the photocell or control box, or is the "pillock" really you ????

Photocell for sure (probably)
John

Boilerman2 said:

Get yourself a "REAL" engineer if the burner Locks out OF COURSE it is oil related!!!!!!! pillock!!

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Even though the burner runs fine for quite some time before locking out? Is there no way the boiler can send some kind of signal to the burner that makes it lock out?

Boilerman2 said:

Your pillock would do well by looking at the photocell or control box, or is the "pillock" really you ????

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I don't see how it could be the photocell. The burner itself is hot and in a steady state for a while before lockout occurs. Also usually the burner will try to relight if it thinks the flame has gone out, right?

Control box sounds more likely.

Boilerman2 said:

or is the "pillock" really you ????

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Ha! No it's not me, I'm not an engineer. I just want it fixed without having to be replaced. For the record the guy has been servicing and repairing it for years before we moved in and seems to know what he's talking about.

Typically......solenoid coils fail when they get warm, and can work perfectly until then
Typically.......photocells allow normal ignition, but the burner locks out after a few seconds if there is a fault in them.
John

Burnerman said:

Typically......solenoid coils fail when they get warm, and can work perfectly until then
Typically.......photocells allow normal ignition, but the burner locks out after a few seconds if there is a fault in them.
John

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Thanks John!

So is the solenoid in the burner or the boiler itself? If it's in the boiler I can see how this might cause the problem, but wouldn't the lack of oil make the flame go out a second or so before the burner locks out?

The photocell could be the culprit but does it usually fail when it's warm?

I'm just concerned with the burner itself here ( red lockout lamp lit on the control box)......if the solenoid coil on top of the oil pump is getting grumpy, often enough the burner will start and continue to run until it gets hot. Then, the thermostats close it down for a time as normal but then it won't light up again when the thermostats ask it to.
The photocell basically looks for light (flame) and if it sees this, it instructs the control box to keep the solenoid activated, and hence the oil flowing.
If the photocell is dud or maybe just dirty, the burner will start but then it shuts down again as the control box assumes that the flame hasn't been established.
In my experience, the solenoid coil is very much affected by heat, and the photocell less so - however any device with electrical resistance ( as both of these devices are) can be affected by temperature changes.
John

HRM field engineers have a neat little test box to check the effectiveness of the cell. Life's too short though so if in any doubt change the cell. It's cheap and easy. Also make sure the inside of the blast tube is not dirty/dull as this can impair light refraction.

If it's a Sterling burner and your Engineer is as good as you say he is he should have all the parts discussed above in his van.

OP you have received a lot of good advice and assistance on this but all you want to do is pick holes in everything you are told
I'M OUT!