Riello burner smoking badly

[Robert]

Hello

I wonder if anyone could answer a central heating question for me.

I have an oil fired boiler fitted with a Riello RD3 burner - that's the later one with the black control box and air inlet on top.

I came downstairs the other day to a stink of kerosene and checking outside black smoke pouring from the chimney. I went through the list of probable causes in the boiler manual troubleshooting section, first replacing the nozzle which made no difference, then replacing the pump which fixed the problem.

The problem that I have is that I checked the delivery pressure of the old pump before I removed it from the burner and it was rock steady at

7.3 bar as per the manual.

I stripped down the pump that I'd removed from the burner. There was no damage or wear that I could see. The only thing that I noticed was a thin brown coloured deposit coating all the surfaces within the pump but not blocking any ports or anything like that. It was easily removed by washing all the bits and pieces in clean kerosene.

So my question is could the pump show the correct delivery pressure on the gauge yet deliver the wrong pressure at the nozzle or do I have some other intermittent fault that's likely to rear its ugly head again in the future?

Many thanks

[John]

The correct pressure at the pump should be the correct pressure at the burner. when you replaced the nozzle did you do anything else such as decarbonising the blast tube head, cleaning out the air inlet ports of fluff, cleaning the fan blades, etc or perhaps these were done in the process of changing the oil pump? While you were about it did you carry out the rest of the service such as opening up the combustion chamber and cleaning out the flueways and baffles? What model of boiler is it BTW?

[Robert]

Thanks for taking the time to reply John.

The boiler is a Potterton Statesman. I followed the trouble shooting guide in the boiler manual which appeared to eliminate everything apart from the nozzle, solenoid valve and pump. Before I did anything at all I put a gauge onto the pump to check the output pressure which was 7.3 bar and correct to the manual which I thought meant the pump was probably OK.

I then removed the burner and opened up the combustion chamber which was packed with soot and the combustion head was covered in it also although only heavily caked on the outside of the tube and not that bad on the inside. After I had cleaned out the boiler and swept the chimney I dismantled the burner looking for any damage, wear, dust and lint accumulation, internal leaks etc and couldn't find any problems. All the airways, damper, fan etc were quite clean.

I then replaced the nozzle, fired up the boiler and drew off a flue gas sample through a filter and improvised pump. The filter was heavily contaminated with soot.

I next replaced the pump, set the pressure to 7.3 bar per the manual and drew off another flue gas sample which was completely clear of soot.

The boiler was serviced in October 2005 and required just a quick brush and vacuum of the combustion chamber at that time. The baffles were all quite clean and no adjustment was required to either the pump or the air setting.

I don't know if it's relevant but I'd had an oil delivery 10 days previously. I've taken a sample and by the smell, feel and yellow marker it appeared to be kerosene.

The boiler has been running faultlessly now for 3 days but what worries me is that there is an intermittent fault present that might suddenly reappear.

Thanks Robert

[Dave Liquorice]

That would have stired the tank up nicely, especially if it was pretty low. Maybe some gunk was in the wrong place upsetting the fueling of the boiler but to be honest I'd expect that to make run weak not rich.

Lots of soot is indicative of not enough air for the amount of fuel so you get incomplete combustion. I wonder if a partial blockage of the jet, so you don't get proper atomisation would have the same effect? ie big blobs of oil that can't burn properly.

[Fatboise]

Robert, Is there any chance that you could have been dissolved suga into the oil tank by accident or even on purpose I think I read som where that this can cause a lot of black smoke?

-- Fatboise