Does anyone know why an Riello RDB boiler would start pluming black smoke?

[SJB060685]

it seems to be getting too much oil to burn either the solonied is not shutting or the needle valve on oil pump is faulty or sticking its a fairly new burner probably 18 months old this behavior started very suddenly according to the owner

Riello burners and pumps do things differently than say their Danfoss cousins. When the solenoid de-energises the stem opens up a port. If the pump is letting by its the regulating spool and not the stem.
Check two things.
1. Do you have a wash pressure and whats operating pressure?
2. If spool is letting by, before bringing on for ignition check inside chamber refractory base and blast tube for signs of oil drip over night, or between demands.
If spool is letting by then you will get large plumes of smoke. You could also have a duff nozzle, bad oil batch or even traces of water could cause it.
Attached is a basic diagram of Riello pumps for your own benefit.

 

[John.g]

SJB, is it true to say that the solenoid valve is opened until the pre purge period is over (~12 secs) and produces this wash pressure of ~ 4 bar?, during this period what prevents oil from flowing through the nozzle? is a port shut off by the solenoid until it shuts which then opens this port to the nozzle and closes the port to recycle?.
Where did the word "wash" originate?.

 

[SJB060685]

Riello pumps do things differently my friend as I said above. During pre purge you have oil being circulated around the return line. Pumps take in a set capacity each second, during pre purge the oil is going around the circuit and back through link between return and inlet. This capacity generates the wash pressure on Riellos (some Suntecs work the same). When the usually NO coil energises it closes the the return port, which in turn takes on more oil from the inlet and raises pressure. When the pressure set by regulating spool is achieved it opens the regulating spool allowing flow to nozzle, any unwanted excess oil is circulated back to return. At no point during pre purge should the oil pressure be enough to open spool and go through to nozzle.
Pre purge is 14 seconds yes (varies on different control boxes) and the wash pressure on Riello is about 2 bar for RDB and up to 5 on old Riello's

 

[John.g]

Thanks for that, I actually have a Riello G5X (Firebird SE 90s boiler) and in its 15 years of operation it has never and I mean never failed to start or tripped on flame failure which is remarkable.

 

[SJB060685]

Regularly maintained boilers are less likely to fail. Of course some will prove problematic regardless

 

[John.g]

IMO, a lot of damage can be done if/when the oil runs out, some will repeatedly keep depressing the reset button on getting a refill without first venting the air from the oil line.

 

[SJB060685]

An oil pump should not run for more than a couple minutes without oil, doing so will wear the pump out. Too many homeowners press the reset button multiples times causing damage to it

 

[jom]

An oil pump should not run for more than a couple minutes without oil, doing so will wear the pump out. Too many homeowners press the reset button multiples times causing damage to it

thanks for that advice will change oil pump and solonied that should sort it hopefully jom

 

[SJB060685]

thanks for that advice will change oil pump and solonied that should sort it hopefully jom

I cant be certain its the pump at the moment, there are other things that could cause this as I said mate. Have you checked for signs of oil dripping out of nozzle when not running? Have you checked nozzle assembly hasn't failed? Have you changed the nozzle? Changing pump might cure it but I'm not saying it will at the moment