Wocester Danesmoor WM12/19 flue temperature

[jake272005]

Hi
The flue temperature of my Worcester Danesmoor WM 12/19 oil burner is overheating so that the flue stat trips regularly. I have changed the nozzle and reset the C02. It should run at around 210C but its currently higher at nearer 230C on occations. New baffle fitted,rope seals all changed etc.
I have reduced the oil pressure down fom the recommended 15bar down to 10bar in a effort to reduce it and the C02 is correct at under 12%. Can I keep reducing the pump pressure or any other suggestions.

 

[kimbo]

have you cjecked your manual for the correct settings

 

[kimbo]

looking at the manual at 105psi you should get a flue gas reading at about 200c with a co2 of 10.5 this depends on what nozzle you have and if you are stating the right boiler. You will need to check the manual 15 bar is too high even for gas oil which is about 12 to 14

 

[jake272005]

Hi Kimbo

Thanks for quick reply

The manual says 140PSI /210C and 11% C02 using Danfoss 0.50 60deg ES nozzle set up for the factory 17Kw output. I was slightly out when I stated 15 bar. It starts up easy and will run for a few hours and then trips every hour or so. Reset the manual reset and its for another hour maybe two but sure as sure it will off the next day after an hours run in the morning. In case you are wondering I am a very old retired plant Engineer.

 

[kimbo]

I doubt whether you have a flue stat as they are usualy only used on their latest condensing boilers. Are you referring to the overheat stat.
How old is the boiler.
It would help if we knew at what temperature the stat is tripping out at as I would suspect it was either the overheat stat or control stat that would need renewing, it is a common thing for them to go.

 

[jake272005]

Hi Kimbo

It looks from the picture in the manual that the reset button goes to the "duct manual reset thermostat", but I will check in the morning. The boiler is about 8 years old and been serviced every year but about a week ago I woke up to find soot all over the place,so I cleaned everything up in and out,replaced the baffle that had rotted,changed the nozzle,checked the pump pressure and set set the CO2 up with my trusty Testo 325 unit and then the stat started giving me hassle. I was told by a Worcester service engineer that these units all "run too hot and are trouble". So you see my thinking. Should I just change all three stats and start again? Appreciate your advice. Regards Jake

 

[kimbo]

Ideally I would check the thermostat pocket with a thermometer to see at what temperature the stat trips out at, this would then tell you which stat (assuming it was a stat problem) was causing the problem, in other words if it was tripping out at 105degc it would tend to point to the control stat not turning of at 80deg etc and that the overheat stat was doing its job. the stat temp settings should be in your manual.

 

[jake272005]

Hi Kimbo
Good point, I will get on to it. I have a new control stat "in stock somewhere" (garage!) but not sure if my old thermo is around these days? I will post the outcome in due course but you have put me on the right track. Never too old to learn (or listen!) Thanks again and regards Jake

 

[jake272005]

Hi Kimbo
Just to update you dropped the oil pressure to 90psi and not the 140 psi as the book says, reset the CO2 to give aroud 90% efficiency overall and its been working without a problem since. The flue gas temp remains within limits. Thanks for your assistance in solving this problem

 

[Worcester Man]

Hi
There is no flue stat on the Danesmoor. Is it a 15/19

 

[Worcester Man]

sorry just noticed you got wall mounted. they are forever sooting up

 

[Worcester Man]

I might pop the pressure up slightly. Just to 100psi. 90 is a tad low

 

[lance]

I always put a .40 nozzle in these, any bigger and the square baffle is destroyed. I know what the book says. Well its all rubbish.
Never had a duct stat go. But if it does ..change it. If its the hi limit one, change control stat pt no 87161423090 .

If you read the small print on all these manuals.... gas temp is for "general guidance purposes only"

 

[jake272005]

Hi Worcester man
Technically your correct its a "duct manual reset thermostat" but it works the same in that it tells me that too much heat is wasted going out the balanced flue.
Regards,Jake

 

[leedufty]

Jake

Did your solution work - i have the same problem even with the boiler thermostat turned to its lowest it will need resetting every couple of hours - if i turn up the thermo its goes even quicker.

Regards

Lee

 

[jake272005]

Jake

Did your solution work - i have the same problem even with the boiler thermostat turned to its lowest it will need resetting every couple of hours - if i turn up the thermo its goes even quicker.

Regards

Lee

Hi Lee,

I have keeped the oil pressure at around 100 or even a tad under and this has maintained the flue temperature and CO2 with limits, I still have to clean the whole kit religiously and change the nozzle every year or when I notice the flue starts smoking a bit. Its still a work around and I know its not correct but its how I manage.
Regards
Jake