Motor running but not firing

Wearb

Can someone advise me please? An a RDB 2.2 burner mostly starts ok, but every now and then (some times after running ok for lots of days) the motor runs, but does not fire up. By the time I get to have a look, it has started working ok again. It does not lock out either and will happily stay running without firing. I thought that in circumstances like this that it should lockout after about 20 seconds or so. Every time I go to look at it, it is running ok, so I don't know where to look for fault. The pump pressure is OK and when burner runs it runs and heats perfectly.

Any ideas please? Should it lockout under those circumstances?

Wearb

BTW, just in case this is of any use to anybody; while recently fault finding on a grant 50/70 modular boiler, I discovered that the fault was that when the system got hot one of the HT leads (which was close to the electronic eye was expanding and covering the eye. When I unplugged the wire and replaced it after rotating it 180 degrees (so that the curved part was now facing away from the eye) it ran perfectly and 2 months later is still going fine.
Maybe something to watch out for. Might help someone.

To better explain: The wire was travelling in a curve from the transformer to the electrodes. When heated the wire lengthened (or softened) slightly, either way it allowed the curve to move out to obstruct the photocell.

Billy Bunting

Wearb wrote: »

the motor runs, but does not fire up. ?

Photocell.

Wearb

Billy Bunting wrote: »

Photocell.

Thanks for reply. Can a photo cell give intermittent trouble, i.e. work OK for days and then not work once or twice and then work OK again? Also can motor stay running without lock-out on a photocell fault? Anyway it will be an easy replacement to try.

Billy Bunting

The RDB photocell does have an issue that on occasions it will signal that it is seeing a flame its not usually intermitent but its quite common, when its persistent, if you disconnect it from the control box, run the burner, once ignition is established quickly reconnect the photocell, it will run until stat satisfied, that will normally prove the point and you can order the part.

Wearb

Billy Bunting wrote: »

The RDB photocell does have an issue that on occasions it will signal that it is seeing a flame its not usually intermitent but its quite common, when its persistent, if you disconnect it from the control box, run the burner, once ignition is established quickly reconnect the photocell, it will run until stat satisfied, that will normally prove the point and you can order the part.

If I can get the fault to replicate itself when I am present, then I will try that. I am still worried that it might be control box. I would expect a lockout on a fault such as you describe? Does the pump valve stay closed to prevent the nozzel spraying oil all over the combustion chamber, because the motor has continued to run without firing. Sorry for so many questions, but I am having trouble understanding the exact sequence of events to be expected with a photocell fault. Especially when the motor continues to run.

Billy Bunting

Solenoid valve isn't opened. This has been a fault discused here in the past. You sound like a person who does a bit on burner, a photocell change for €20 and see if the fault reacures, if it does then you have a spare photocell.

Wearb

Billy Bunting wrote: »

Solenoid valve isn't opened. This has been a fault discused here in the past. You sound like a person who does a bit on burner, a photocell change for €20 and see if the fault reacures, if it does then you have a spare photocell.

Thanks. I will do that. I have a photocell on an old spare burner that I rebuilt and keep for spares or emergency replacement.
I amazed that Riello haven't changed the control box set-up to lockout the burner on such a fault and not have the pump churning away under pressure. Cant be good for the pump.
Thanks again. I will post back eventually. I may leave it to see if the problem becomes more persistent. As it stands, I could make replacement and not know for over a week if that was the cause.

DGOBS

A faulty solenoid can also cause this constant pre-purge, as can the control box, and PE cell as stated above.

I have had this several times as a control box fault (dry solder??), especially when so intermittent

jimf

another but unlikely intermittent break down of voltage from motor to control box 53v white wire

Wearb

DGOBS wrote: »

A faulty solenoid can also cause this constant pre-purge, as can the control box, and PE cell as stated above.

I have had this several times as a control box fault (dry solder??), especially when so intermittent

Thanks. I will go one step at a time starting with the cheapest part. Fingers crossed that I don't eventually replace the control box and still have a problem

Wearb

jimf wrote: »

another but unlikely intermittent break down of voltage from motor to control box 53v white wire

Thanks. It just gets better all the time.
I did get correct voltage on the white wire, but then it was running OK at THAT time.

shane0007

If the fault happens, disconnect the photocell cable from the control box. If it goes to lock out, replace the photocell. If it continues to run, replace the coil. If it still continues to run, replace the control box.
The reason it does this is the control box knows it is getting a false signal from the photocell. At that stage of the ignition process, the control box is looking for darkness, i.e. no flame. If it does not confirm this, then it will keep the motor running, i.e. the fan, to blow out a flame that maybe established. It is a deliberate safety feature and not something that needs to be changed by Riello!

Wearb

shane0007 wrote: »

If the fault happens, disconnect the photocell cable from the control box. If it goes to lock out, replace the photocell. If it continues to run, replace the coil. If it still continues to run, replace the control box.
The reason it does this is the control box knows it is getting a false signal from the photocell. At that stage of the ignition process, the control box is looking for darkness, i.e. no flame. If it does not confirm this, then it will keep the motor running, i.e. the fan, to blow out a flame that maybe established. It is a deliberate safety feature and not something that needs to be changed by Riello!

Thanks. I will try that.
I don't understand how the control box knows its getting a false photocell reading, but that is for another day. I will try and get to this boiler when it is in one of its not firing humours.

shane0007

It is measuring resistance via lux. It will depend on the fault of the photocell that determines the reaction of the control box. Some photocell faults will result the control box putting the burner into lock out.

Wearb

shane0007 wrote: »

It is measuring resistance via lux. It will depend on the fault of the photocell that determines the reaction of the control box. Some photocell faults will result the control box putting the burner into lock out.

Thanks for that explanation. I didn't know that the photocell sent variable signals to control box. I thought it was either seeing light or not. Knowing that it returns results more complicated than on or off will be helpful in the future. Thanks for going to the trouble of explaining that to me.

Wearb

I have changed photocell, coil, control box and now pump. I don't expect the pump to solve the problem, but will see.

I still haven't gotten to the system when it has been faulty. Every time I called it was working. I would like to get a voltage reading on the white wire while it is misfiring.

Exact symptoms are: starts, fires up with flame established, about 10 seconds later flame goes out but motor keeps running, after about 10 seconds flame re-establishes and the whole cycle continues (until a few minutes before I arrive to check it, by which time it is running perfectly)

It has been most (but not always) problematic in the early morning, which leads me to believe it may be an air fuel mixture problem, but I have set it up according to the manual (used analyser). If still giving trouble, I will try it with a hollow nozzle (solid recommended) and set it up for that. After that I am out of ideas.
Would REALLY appreciate any suggestions.

jimf

what boiler is this fitted to is it balanced flued any chance of flugas recycling being the cause

Billy Bunting

Wearb wrote: »

Can someone advise me please? An a RDB 2.2 burner mostly starts ok, but every now and then (some times after running ok for lots of days) the motor runs, but does not fire up.

You are now changing the story......

Wearb wrote: »

Exact symptoms are: starts, fires up with flame established, about 10 seconds later flame goes out but motor keeps running, after about 10 seconds flame re-establishes and the whole cycle continues (until a few minutes before I arrive to check it, by which time it is running perfectly)

I agree with Jim, a little more presice information would help......

Wearb

jimf wrote: »

what boiler is this fitted to is it balanced flued any chance of flugas recycling being the cause

Balanced flue. Warmflow 70/90 boiler. Nothing changed in years that might cause this to be Flue gas recycling.

jimf

wearb

your last post could possibly indicate an overaired burner or fluegas recycling but if set up with fga and your happy with readings then it
should not be overaired

post your fga readings and pump pressure

jimf

Wearb wrote: »

Balanced flue. Warmflow 70/90 boiler. Nothing changed in years that might cause this to be Flue gas recycling.

again not enough info is it boilerhouse or what

Billy Bunting

Module, Utility or Boilerhouse model ?

Wearb

Billy Bunting wrote: »

Module, Utility or Boilerhouse model ?[/Quote

Not have readings to hand. But I know that pump at 8 bar and got best overall fg readings at 11.7 co2. Boiler house model. Good air vent on boiler house.

Excuse slow reply. I am using my tiny buttoned phone

jimf

Wearb wrote: »

Billy Bunting wrote: »

Module, Utility or Boilerhouse model ?[/Quote

Not have readings to hand. But I know that pump at 8 bar and got best overall fg readings at 11.7 co2. Boiler house model. Good air vent on boiler house.

Excuse slow reply. I am using my tiny buttoned phone

i know this might sound extreme but do you have a PROVEN spare burner to exchange if same problem persists then you know for sure its not a burner issue
and you have to start looking elsewhere to be honest you nearly have a new burner fitted already with the earlier mentioned parts

its jobs like this that make you sorry you didnt bring the sledge

Billy Bunting

Are you using the snorkle on the flue ??

Wearb

jimf wrote: »

Wearb wrote: »

i know this might sound extreme but do you have a PROVEN spare burner to exchange if same problem persists then you know for sure its not a burner issue
and you have to start looking elsewhere to be honest you nearly have a new burner fitted already with the earlier mentioned parts

its jobs like this that make you sorry you didnt bring the sledge

All those parts came off a working burner. If still giving trouble after pump change, I will put them all back on my burner and fit it to the system. It just might be a faulty feed from motor to control box.

What do you think of trying a hollow nozzle before I do that?

I really really would like to take a sledge to it. Especially if the pump solves the problem, because the owner was insisting that it was the pump from the start. He was basing this assumption on a neighbour having had a boiler problem that was fixed by a pump replacement. If pump solves it, my name is kaput there. Still, my first responsibility is to fix it and try and mend fences afterwards.

(in case that last statement (neighbours pump) leads you to suspect an oil contamination problem, the last delivery was 7 months ago and tank is still half full. Filters spotless, no water showing on paste)

.jacksparrow.

Wearb wrote: »

jimf wrote: »

All those parts came off a working burner. If still giving trouble after pump change, I will put them all back on my burner and fit it to the system. It just might be a faulty feed from motor to control box.

What do you think of trying a hollow nozzle before I do that?

I really really would like to take a sledge to it. Especially if the pump solves the problem, because the owner was insisting that it was the pump from the start. He was basing this assumption on a neighbour having had a boiler problem that was fixed by a pump replacement. If pump solves it, my name is kaput there. Still, my first responsibility is to fix it and try and mend fences afterwards.

(in case that last statement (neighbours pump) leads you to suspect an oil contamination problem, the last delivery was 7 months ago and tank is still half full. Filters spotless, no water showing on paste)

Ah the usual,the owner already has it solved so what's the need for you?that does my head in when they try tell you what's wrong before you even have a look.

Have you changed the control box?

Wearb

Billy Bunting wrote: »

Are you using the snorkel on the flue ??

SORRY the above question just made me realise that I previously answered incorrectly about it being a balanced flue (I must be going demented over it) It is a low level flue with air being drawn in through an air vent on the opposite side of the boiler house.


Also, perhaps I should mention that original setting on air adjuster was 6.5 when I first called and I have now set at 4.5 after using smoke pump and analyser. I didn't use analyser until using the smoke pump, but can only assume that there was way too much air originally, though it ran for 10 year at that setting. I had to turn the air down to almost 4 before I got staining on the smoke filter paper.
I did open the air chamber to check fan and proper functioning of air adjuster. One time found a feather in there that was causing all sorts of intermittent problems, but that was on a different boiler.

Wearb

.jacksparrow. wrote: »

Wearb wrote: »

Ah the usual,the owner already has it solved so what's the need for you?that does my head in when they try tell you what's wrong before you even have a look.

Have you changed the control box?

Yep. Motor and electrodes are all that have not been replaced now.

.jacksparrow.

Wearb wrote: »

.jacksparrow. wrote: »

Yep. Motor and electrodes are all that have not been replaced now.

Have you checked inside the boiler?could be getting blowback.