Another weird Riello oil burner issue.

[reb78]

I have another boiler issue. Riello RDB burner on a grant boiler. Its firing for about 2-3 seconds then it stops. Fan continues running and then it fires again for a couple of seconds. Its not locking out as apparently its being doing this for some time. Oil supply is good. Its running on heating oil.

Any ideas? I havent investigated further yet.

 

[reb78]

Pipes are all hot and system pressure is fine.

 

[waddycall]

It’s probably one of three things -
Solenoid
Photocell
Control box

Needs a pressure gauge fitting to it to see if the oil pressure is dropping off. Alternatively look through the end of the burner and see what the cycle is.

 

[Onoff]

Photocell - tug, wipe is the first thing. You can check resistance with a strong light etc.

Solenoid - you can check for resistance / open circuit.

Pressure gauge, an absolute boon to diagnosing these. This is the one I have:

BES.co.uk | Next Day Delivery On 15,000 + Plumbing Supplies

Order oil pressure gauges from our gas and plumbing supplies range online at BES. Free next day delivery available. 15k+ Products in stock. P/N: 18582

www.bes.co.uk

Don't know what your model is exactly but there's likely a fault finding chart like this PDF that gives resistances:

 

[reb78]

Thanks folks.

Weird it isnt locking out?

 

[reb78]

The photo cell was filthy. Weird as this was all setup in spec by an engineer who knows what he is doing before Christmas.

Lets see if a clean fixes it.

This boiler is specced to do two properties. I have people in one who insist on having the heating on 24/7 amd controlling it via the thermostat. Once the house is up to temp it only needs short top ups of heat as it heats up quickly so what they are doing makes the boiler come on for short bursts all the time. They wont do as I ask and set the heating for defined periods so the boiler has a good burn each time it comes on.

 

[carbon]

If it has a balanced flue check there isn’t an issue with that mine was doing the same thing some years ago. A small plate had dropped off and allowed it to draw the exhaust fumes back in. The lack of oxygen stopped it burning, it would then relight and repeat the process.

 

[jenki]

Not sure if I have already suggested this but the plastic/nylon drive coupling on my burner oil punp caused lockouts numerous times why such a seemlingly simple part should; I have no idea. Also check you have the correct capacitor value there are 2 to the best of my knowledge.

 

[voipio]

Could the present windy conditions have anything to do with flame stability?

 

[reb78]

Could the present windy conditions have anything to do with flame stability?

I did wonder this. Its outside although partially sheltered by the building it heats.

 

[reb78]

Not sure if I have already suggested this but the plastic/nylon drive coupling on my burner oil punp caused lockouts numerous times why such a seemlingly simple part should; I have no idea. Also check you have the correct capacitor value there are 2 to the best of my knowledge.

I had a capacitor issue before Christmas so think this is ok.

 

[Onoff]

Get a pressure gauge and set it up properly, 8bar it my case. If could be running rich. Do you recall the engineer doing so?

On mine, an RDB2, the pressure adjustment gauge is the black slotted screw inside the black nut above the brass hex extension:

https://flic.kr/p/2pGiG5d

 

[Onoff]

Jet too is worth a look. Mine had been running for years with the pressure slightly off:

https://flic.kr/p/rf4CDE

https://flic.kr/p/rumdjY

 

[waddycall]

Best not to adjust anything unless you have the means to test it properly i.e. flue gas analyser and smoke pump. Good point about the flue recirculating.

 

[waddycall]

I’m an ex boiler engineer. My grant oil boiler is not set up exactly to spec. It has a smaller nozzle running at a higher pressure to give the correct flow rate and heat input. Sometimes it’s necessary to do the opposite. Oil pressure affects flow rate so if you change the oil pressure the air setting will be out. You really need the right gear to set them up properly. Before electronic analysers chemical ones were used.

 

[reb78]

Dont worry. I quickly realised that pressure and air both need adjusting and you need the flue gas analyser to do that.

This was all setup properly. We put a slightly smaller nozzle in IIRC to get it to burn for longer to counteract the short burns with the larger nozzle (due to the way the occupants insisted on using the central heating) but it was setup according to the specs. I with him the whole time as he is a friend and we chatted through it. If cleaning the photocell hasnt fixed it I will give my friend a call tomorrow.

(I do recall that he commented that the swirl tube was possibly too long (?) for the nozzle he put in but didnt think it would cause an issue. Could that be a problem?)

 

[waddycall]

If the smaller nozzle means reduced air setting the pressure drop through the diffuser might not be high enough to get good mixing so it could soot a bit. Depends also on whether or not there is an adjustment for head setting on the burner. Trouble is no one uses a smoke pump anymore. It’s assumed that if the CO reading is ok it’s not sooting which isn’t necessarily true.

 

[gaz1]

This boiler is specced to do two properties. I have people in one who insist on having the heating on 24/7 amd controlling it via the thermostat. Once the house is up to temp it only needs short top ups of heat as it heats up quickly so what they are doing makes the boiler come on for short bursts all the time. They wont do as I ask and set the heating for defined periods so the boiler has a good burn each time it comes on.

fit a timer on there line so it only fires up after a cool down period per hr can be done easily

this is how you will get what you want

all it does is go inbetween the calling for heat line and sets it with use with a timer unless you switch that timer to constant it will stop that thermostat calling for heat all of the time

 

[reb78]

fit a timer on there line so it only fires up after a cool down period per hr can be done easily

this is how you will get what you want

all it does is go inbetween the calling for heat line and sets it with use with a timer unless you switch that timer to constant it will stop that thermostat calling for heat all of the time

Thats not a bad idea. Got a link to one?

Luckily they move out soon so I wont need to be told how best to use my own heating systems...

 

[gaz1]

you will find it by 2 ways

thermostat to timer via the boiler wiring diagrams

External programmers for combination boilers

Connecting a single channel programmer and room thermostat to a combination boiler

flameport.com

or by cylinder stat to timer

security light timers can also be used

security light timer wiring - Google Search

those multi switches can be set for every 1/4 of an hr so the cool down period can be set for every half hr or every 1/4 of an hr to fire up

a note must be said if you get any worker that comes in and fires the boiler up by the thermostat that timer will over ride it until its on position has been met it will then fire for 15 mins then turn off or whatever your settings are going to be