HRM Wallstar won't ignite

[Lancashirelad]

Hi all. Would appreciate your thoughts on this as I'm currently sitting in a very cold house. Apologies for the long post, but need to present the facts.

This boiler has now been temperamental for 2 winters.
Its 21 years old I'm aware that means its at the end of its expected life, however it is somewhat of a meccano set with no part that cannot be replaced.

I am not a qualified oil boiler engineer, but an old style vehicle mechanic. I've have been maintaining/trouble shooting this boiler for about 18 years so we are quite well acquainted.

When the temperature is milder, say above 7*C performs almost faultlessly, as soon as it goes cold, it frequently fails to start and/or keep running and goes to lockout. Up until yesterday, would always go on reset.

Over the past few years it has had:

control box (probably unnecessarily)
pump c/w solenoid
transformer
capacitor

Recently had an experienced engineer to it who fitted a new nozzle and at my request checked flu temp and soot. Temp was spot on, (I forget what he said, would it be 300*?) Then ensued a conversation about wasted heat and flu gas recycling. Soot test was clear.

Since he came the weather has been mild and apart from the occasional lock out, its been fine.

Now the temp has dropped to zero and I can't get it going at all. Neighbour saw me fiddling with it came round and said "You've never failed to get it going before".

On attempting to start:
It purges, so the motor is starting, solenoid opens & delivers fuel - high pressure pipe union slacked off to check, so pump is working.
There is a spark at the electrodes, (tested in free air) which I think are set correctly. BUT, no flame.

There are no issues with the fuel supply, I have a transparent loop with no bubble. (not that it would matter if there was a bubble). Currently the tank oil level is above the burner.

I'm lost, I have fan, pump, fuel and spark, yet no ignition.
Once the solenoid clicks unburnt vapourised fuel is expelled from the flue.

Is the fan blowing out the spark?

Over the past few days I've noticed sometimes when the boiler is cold the flame goes out but reignites before the photocell has chance to tell it to shut down. This will happen repeatedly until it gets warm.

 

[simb82]

what was the co2% in the flue gas?
sounds as if its burning to lean. 300 is too hot.
Take a note of the air damper setting, then close it slightly.
a little bit at a time, to see if that improves ignition.

or use your fga to check co2 is 12%...

 

[MANDATE]

Could be worn pump not delivering at the correct pressure.
Could be the position of the spark across electrodes. If too far behind the oil spray it would be more difficult or impossible to establish a flame.
Could solinoid be affected by cold weather on initial attempts to start up.
In the past I have removed power from my boiler. Then used 3 separate switched supplies to operate transformer, pump and solinoid.
This way I could check each separately and combined without the control box or photo cell

 

[dcawkwell]

Invariably it is fuel problems of some sort with it being wall mounted.
Things to check/replace. Non return valve (consider fitting a tiger loop).
Air leaks in the oil line. Pump pressure.

Remove the burner and test fire.
Is there any fuel being sprayed?

If non fuel take oil hose from burner put it in a can of oil above the burner with a little air bleed it should fire straight off if the pump is working.

 

[Lancashirelad]

Could be worn pump not delivering at the correct pressure.
Could be the position of the spark across electrodes. If too far behind the oil spray it would be more difficult or impossible to establish a flame.
Could solinoid be affected by cold weather on initial attempts to start up.
In the past I have removed power from my boiler. Then used 3 separate switched supplies to operate transformer, pump and solinoid.
This way I could check each separately and combined without the control box or photo cell

Thanks for your reply. The tip of the electrodes are about level with the front of the nozzle. Should they be slightly further back? I'll try to upload a photo soon.

At present (i.e. not starting at all) the solenoid can be heard to click after purging, high pressure fuel then arrives at the slacked off union, or when that is tight, can be seen exiting the flue.

 

[Lancashirelad]

Invariably it is fuel problems of some sort with it being wall mounted.
Things to check/replace. Non return valve (consider fitting a tiger loop).
Air leaks in the oil line. Pump pressure.

Remove the burner and test fire.
Is there any fuel being sprayed?

If non fuel take oil hose from burner put it in a can of oil above the burner with a little air bleed it should fire straight off if the pump is working.

Thanks for your reply. I don't think there is a non return valve fitted, unless its integral in the pump. This boiler has been in situ 21 years and I've never suffered low pressure oil delivery problems. I'll try to upload a pic of the supply pipe. I'm pretty sure its not a low pressure oil delivery issue.

I agree a removed burner test fire might be interesting.
I think its safe to assume fuel is indeed being sprayed as atomized fuel is exiting the flue.

 

[dcawkwell]

Well if you have fuel there is no spark occuring.

Remove burn out form the hole and have a look when it is trying
to fire.

All the burner needs is fuel and a spark.
So if there is fuel there is no spark.

Easy to see this with the burner out (it won't bite. Unless you stand in front)

Invariably it is fuel problems of some sort with it being wall mounted.
Things to check/replace. Non return valve (consider fitting a tiger loop).
Air leaks in the oil line. Pump pressure.

Remove the burner and test fire.
Is there any fuel being sprayed?

If non fuel take oil hose from burner put it in a can of oil above the burner with a little air bleed it should fire straight off if the pump is working.

Thanks for your reply. I don't think there is a non return valve fitted, unless its integral in the pump. This boiler has been in situ 21 years and I've never suffered low pressure oil delivery problems. I'll try to upload a pic of the supply pipe. I'm pretty sure its not a low pressure oil delivery issue.

I agree a removed burner test fire might be interesting.
I think its safe to assume fuel is indeed being sprayed as atomized fuel is exiting the flue.

 

[bernardgreen]

Oil vapour ignites easily but droplets of oil are un-likely to ignite unless it is a spark large enough to vaporise a couple of droplets.

It may be that the oil and or incoming air are too cold for any vapour to form at the nozzle.

Maybe warming the air with a hair drier or similar will help vaporise the oil.

I seem to recall an electrical heater on the nozzle of a boiler intended for use in very cold weather.

 

[Lancashirelad]

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• Lancashirelad
• 29 Dec 2014
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• Lancashirelad
• 29 Dec 2014
• 1

Untitled

• Lancashirelad
• 29 Dec 2014
• 1

Untitled

• Lancashirelad
• 29 Dec 2014
• 1

 

[Boilerman2]

Attempting to fire the burner in the open is NOT something that I would recommend anyone to do - the ignition components operated at around 8Kv, and if the burner did decide to fire you might find yourself in A&E!

also if the Photocell can see daylight, the test would be invalid as the cell would react to "false light"

At the point where the Solenoid operates I would be putting my hand over the air intake on the burner to restrict the combustion air temporarily if the burner fires, it indicates an air rich fuel air mix
The most likely cause of this burner's malfunction is a contaminated Nozzle - try a new nozzle before proceeding any further

 

[Burnerman]

Generalising, the tip of the electrodes are flush with the end of the nozzle, and the gap between them around 2.5 to 3mm.
The draught from the fan blows the spark into the atomised oil spray.
A couple of things to check......the spark should spark, naturally enough, between the electrodes. However, it's not unknown for the spark to jump onto the nozzle or indeed the blast tube if things aren't correct.
A dud nozzle may spray the oil away from the electrode arc, poor oil pressure may cause insufficient atomisation.
For real awkward burners, I fire them up on the bench, with a separate kerosene and mains supply. Covering the photocell by hand allows the burner to light, and then showing the photocell the flame keeps things going.
John

 

[Lancashirelad]

Despite the slight dampness at the joint it can (hopefully) be seen there is no air at all in the supply.

Bernard this boiler has previously worked fine at -10C

 

[Lancashirelad]

Generalising, the tip of the electrodes are flush with the end of the nozzle, and the gap between them around 2.5 to 3mm.
The draught from the fan blows the spark into the atomised oil spray.
A couple of things to check......the spark should spark, naturally enough, between the electrodes. However, it's not unknown for the spark to jump onto the nozzle or indeed the blast tube if things aren't correct.
A dud nozzle may spray the oil away from the electrode arc, poor oil pressure may cause insufficient atomisation.
For real awkward burners, I fire them up on the bench, with a separate kerosene and mains supply. Covering the photocell by hand allows the burner to light, and then showing the photocell the flame keeps things going.
John

Hi John. Yes I'd noticed when testing in free air, when I widened the electrode gap to try to give a bigger spark, because of the kink in the electrode it puts them nearer the nozzle, the spark was then alternating between electrode - electrode and electrode to nozzle, so I sorted that.

Why I'm stumped is because I appear to have both fuel & spark, the required ingredients, yet still no flame.

I tried changing the nozzle for an old one previously removed on a routine service. No difference.

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Oil pressure: I've no means to test. Engineer (who is past retiring age and has worked with oil boilers for many years) said he could tell by the way it was running that it was bob on.

Running lean: I'd agree it may have been. The air adjustment was almost on max. at 10.5. When I cleaned out the flame chamber in the summer, there was no soot at all, just lots of sulphur clinker.

Worn pump: Previous pump lasted about 15 years. This one has been on less than 2 and has not done many hours. Only does a few hours a week for HW in Summer, (alternated with immersion), in winter is only morning and evening.

 

[MANDATE]

Can't agree with your engineer. I was in similar position. A £10 pressure gauge showed my required pressure of 100 psi was 19psl and I could not increase it..
A new pump and my hit and miss problems disappeared.
What size gap have you between the electrodes.seems wide in the photo.
Should be about 3mm

 

[Burnerman]

Alas, we're grasping at straws a bit, I think......I'd like to know what the oil pressure is set at (gauges are around £20) and I've yet to see a burner with the air door open full.
Are you happy with the blast tube position? It's always worth marking them if they don't have an obvious location.
Another straw.....if the motor is slow, the oil pressure is down and so is the draught from the fan.
When the burner last behaved, was there any particular smell from the flue, and finally are you on kero or the heavier burning oil?
John