B20 locking out every 4 months

[freeoil]

50/70kw Danesmoor locking out every 4 to 5 months.Diffuser seems to be sooted blocking pc.Last set up Feb 18.
A/temp 7c
Co2 11.8
Co 24ppm
Oil 155psi with danfos s 1.75 60s.
looked like afterburn so changed solenoid.
Back today to clean diffuser again.
Electrodes 4/5mm apart.1/2mm in front of nozzle .All per M.Is.
Been servicing this boiler for 18years with no faults until now.
Oil pressure steady,clean oil supply and visual inspection of flame is perfect.Oil vacuum and flue draught perfect.Intensive service carried out Feb 18.
My next step might be an oil pump or check nrv before nozzle.
Back in Feb i used a kane 455 and Testo 327-1 and got same resaults.
This has been going on for approximately two years so any help would be great.

 

[Best]

Oil pumps can show a good pressure when burner started initially but then begin to drop in pressure. So if in doubt, then replace oil pump if it is a few years old.
Also is worth checking the nrv.
Is the 155psi to the boiler MIs?
That is high for kerosine.
But - most likely are the following -
Check the burner isn’t pulling flue gases in.
I would be careful about enough air getting to burner.
The Co2 could be lowered a little to see how the boiler is in another few months. I know the MIs probably say 12% for that boiler, but I note your ambient temperature was only 7 degrees, yet you set up the burner at 11.8 % Co2. I would suggest you should have raised the burner air setting to have reduced that to little more than 11% (on low air temperature of only 7 degrees). You will find on a warmer day the reading for Co2 will be very much higher.
But it doesn’t explain why the boiler you have serviced for 18 years is only now giving trouble.

 

[Best]

Just a graph showing intake air temperature to Co2 relation. Quite an increase in actual Co2 from 7 degrees to a more average 20 degrees. I am always wary of using an analyser on oil boilers in cold weather, as the Co2 reading should not be set as high as in the MIs, - which are only a guideline and for average temperatures.

 

[freeoil]

Hi Best.
I appreciate the reply.
Yes 155 psi is from the details on the front stat panel.It's a strange one as I can't work out what's changed.I have serviced it the last 11 years and my father serviced it the previous 7 years so I have its full documented history.I did price a new burner from bassetts back in feb with vat it was £480 .I passed or rather the custard did.
New oil pump im leaning towards.
I think co2 is supposed to be 12.5 don't quote me though as that was 4/5 months ago.
Thanks for the graph.

 

[Best]

Hi Best.
I appreciate the reply.
Yes 155 psi is from the details on the front stat panel.It's a strange one as I can't work out what's changed.I have serviced it the last 11 years and my father serviced it the previous 7 years so I have its full documented history.I did price a new burner from bassetts back in feb with vat it was £480 .I passed or rather the custard did.
New oil pump im leaning towards.
I think co2 is supposed to be 12.5 don't quote me though as that was 4/5 months ago.
Thanks for the graph.

It wouldn’t surprise me if Co2 on MIs is given at 12.5 %.
I was thinking of your issue today and with the age of that boiler I was wondering if the burner motor was operating at full revolutions.
Also, I must have forgot you are a local guy

 

[heliotrope]

I would be looking at the motor and capacitor but in the great scheme of things £480 is a very low price for a new burner for a close on 20 year old boiler,

 

[freeoil]

I would be looking at the motor and capacitor but in the great scheme of things £480 is a very low price for a new burner for a close on 20 year old boiler,

hi Heliotrope.
yes £480 is not bad...I went to a branch recently were the guys are familiar with me and got a significant reduction from the original quote.So hopefully the custard will agree to the new price of it locks out in a couple of months.

 

[freeoil]

Hi Best.
Yes lazy motor is worth considering.
It would have to be intermittent as the soundtrack and visual inspection of the flame are perfect and no movement on f.g.a numbers .
I was also thinking of a bit of afterburn from oil passing the threads of the nozzle.Hence the extremely slow build up of soot on the difuser.I've seen a few Bentones weep in this area but never to lock out.
A 4mm hole drilled in the blast tube inline with the p.c would at least keep it running without any premature callouts between servicing! Lol.

 

[Gasmk1]

i am not oil anymore only did it for a couple of years (hated it) could it be oil level in tank affecting the pump. daft idea possibly but sometimes problems are weird