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Discuss Does anyone know why an Riello RDB boiler would start pluming black smoke? in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

jom

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8
Does anyone know why an Riello RDB boiler would suddenly start pluming black smoke? Does it have anything to do with the needle valve in the fuel pump?
 

SJB060685

Plumber
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2,558
Does it have anything to do with the needle valve in the fuel pump?

Have you been fiddling with the pressure regulator?
Pluming black smoke can be caused by a number of things. When was it last serviced? Has anyone been playing with it?
 

SimonG

Esteemed
Plumber
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20,531
The longer it smokes black the more expensive it is to repair. That's how I work it.

Sounds like somebody's been fiddling! Run out of fuel?
 

SJB060685

Plumber
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2,558
The longer it smokes black the more expensive it is to repair. That's how I work it.

Sounds like somebody's been fiddling! Run out of fuel?

I wholeheartedly agree mate, if left unattended this will cost more than a routine service.
 

SJB060685

Plumber
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2,558
A sooted up toaster is bad enough, a sooted up steamer secondary HEX thats got the soot wet and set is horrible.
[automerge]1590338125[/automerge]
there was nobody near it

Ok. I suggest getting a reputable engineer in out to service it and give everything a look over.
Have you had a recent delivery of oil?
 
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jom

Messages
8
there was nobody near it
A sooted up toaster is bad enough, a sooted up steamer secondary HEX thats got the soot wet and set is horrible.
[automerge]1590338125[/automerge]


Ok. I suggest getting a reputable engineer in out to service it and give everything a look over.
Have you had a recent delivery of oil?
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
 

SJB060685

Plumber
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2,558
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.
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John.g

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2,832
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

Plumber
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2,558
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

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2,832
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

Plumber
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2,558
Regularly maintained boilers are less likely to fail. Of course some will prove problematic regardless
 

John.g

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2,832
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

Plumber
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2,558
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

Messages
8
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

Plumber
Messages
2,558
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
 

John.g

Messages
2,832
If the pump hasn't been run dry due to a frequently empty tank then it may be ok, could possibly be partly sticking solenoid, on my GX5 burner there is a very sharp distinct click when the solenoid is energised closed after the purge period. Maybe worth fitting a new nozzle and getting the pump pressures checked by someone before spending a fair bit of money.
[automerge]1590446119[/automerge]
One other item, on some of these modern burners I think that they are also fitted with a air intake shut off damper opened with a hydraulic ram by the pump pressure, might also worth checking this out in case its not opening fully and throttling the air.
 
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SJB060685

Plumber
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2,558
John the hydraulic damper you mention is found on older Mectron burners, not the RDB this burner is. Firebird did install a damper if you will on BF snorkels, until they realised it caused my problems than answers. The type of design you mention is also found in some Riello two stage commercial boilers but no modern domestic PJ burner does this that i know of.
Smoke and soot emissions are down to either an excess of air affecting flame pattern and causing combustion issues, or more commonly an air deficiency, resulting in high CO2 and smoke emissions. Knowing that one then needs to think of all the things that could cause this.
 
G

gilt279

I had a riello burner on a grant combi boiler. A metallised sticky label fell off of the heat exchanger, when it got hot, and landed on the burner air inlet, restricting the air, and suddenly causing sooty smoke.
 

John.g

Messages
2,832
Attached is a interesting piece re oil pumps in general, I can now see where the Danfoss regulating valve works in the "opposite" way to the Riello, see post #11, above, for Riello Pump schematic.
 

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SJB060685

Plumber
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Have a look through the whole article John, I've had it saved as a PDF on my ipad for some time. Its very interesting and gives you lots of information from different pump type schematics through to how resistance is generated in the suction line and a whole lot more.
 

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