Wallstar oil boiler locking out

[nodiyer]

Please bear with me on this I will try to keep it short! wallstar boiler 5 years old. 18 months ago started to cut out. Practically all parts except burner have been replaced. I have been trying to monitor it to see if there are any recurring themes when it cuts out but no. It was cutting out practically daily until around March/April. Since then only really the Hot water has been on and it was fine. Now and again we put the CH on but the thermostat was low and it did not cut out. Last week temperatures seemed to plummet and up when the thermostat. Bang off it went. So I tried to test my theory every which way with different thermostat settings. The blooming thing would not cut out! So maybe I had it wrong. All ok for a while then last night it went again. Thermostat was at about 26 (needs to be high as front room really cold) Reset the boiler and within minutes it went again. This happened twice. Although the thermostat was at 26 the clicking point was at 22 so I turned the thermostat down and the boiler reset itself!!

I have not had a chance to test this yet but I was wondering if anyone has heard of this before? Is it the thermostat? Does the boiler reset itself?

Any help would be greatly appreciated as I am at my wits end. Everyone says what a great boiler this is but for me its the biggest pain in my life!

 

[Nixt]

Do you re-set it from burner lockout or overheat thermostat? Both do not re-set themselves on Wallstar.

 

[Agile]

Has the burner and the flame detector been serviced?

Tony

 

[nodiyer]

Thank you for the quick reply guys. Firstly I reset it on the outside wall the button goes orange. Press that and it fires up fine.
The boiler is serviced yearly. I cannot comment on if the burner and flame detector has been serviced. But I did have an engineer trying to resolve the problem so hopefully he looked at that. Would that tie in with the high temperature?

The problem is that it is intermittent and never goes completely so it is really difficult to indentify the problem. You don't know if it is working because it is just working or if you have fixed something. Then it goes again.

 

[Nixt]

The outside wall re-set is the burner lockout (You would remove grey case to access) If so and lockout is symtom each time, the fault is burner/fuel related only and has nothing to do with any part of the central heating system. Check the clear fuel line to burner is not full of air bubbles.

 

[nodiyer]

Hi Nixt, yes there is air in the fuel line but it has been ruled out as being the problem.
If this was the problem though why would it work all summer for the HW and the CH on a lower temperature? If there was too much air would it not eventually fail to restart?

 

[Nixt]

No it makes no difference. If there is a static air bubble about 10-20mm long and oil under it its OK but a stream of bubbles or large air gap will indicate it needs purging. If this is permanent it means air ingress on supply line.

 

[nodiyer]

Sorry Nixt, being a bit thick here, but why would the bubble not cause a problem all through the summer (HW heats twice a day and CH on occassionally) but start playing up again now?

 

[Nixt]

The bubble won't ever cause a problem if it is static and single (as in it stays the same size and shape during operation) the oil passes under it. If however during operation the bubbles stream (like fizzy drink) it will cause lockout.

 

[nodiyer]

The bubble is only 1 bubble not loads of little ones. I know this has been looked at before and the NRV was changed. I will monitor it when the boiler is on to see if anything changes. If not any ideas as to what else it could be?

 

[Nixt]

Then assuming it starts each time you re-set, one or more of the following

Dirty photocell, worn drive coupling, partially blocked nozzle, tight spot on fuel pump or problem with POC exit.

 

[nodiyer]

Ok thanks nixt

 

[AlanE]

Burner is fitted with a Danfross oil pump which can be very prone to intermittent lockout due to intermittent solonoid coil.

Next to check disconnect oil line from pump and do you get a GOOD flow. If not check all filters are clean.

The best way to check oil supply problems is with a vacuum guage fitted to oil pump. If you have one what reading do you get?

Control box could be faulty but the only way to check is by substitution.

Hi Nixt, yes there is air in the fuel line but it has been ruled out as being the problem.
If this was the problem though why would it work all summer for the HW and the CH on a lower temperature? If there was too much air would it not eventually fail to restart?

The boiler would tend to run with longer off periods when used for only hot water & CH set to a low level so if fuel restriction is the overall problem these longer periods give fuel supply longer to recover. Again proper diagnosis requires vacuum guage.

 

[Nixt]

Yes AlanE forgot to mention solenoid but should be OK if its firing each time. The oil flow test can only be done if there is available head. Most Wallstars are suction lift.

 

[Eng33]

Had similar problems a couple of years ago, read this:-

//www.diynot.com/forums/viewtopic.php?t=47722

I'd put money on it being the pump, this was the last thing I tried after checking / changing just about everything else! The drive key in the pump rotors had worn to an extent that the inner rotor was not being driven.