Ferroli APS

[Hoffers]

Can any one advise me on how to test the APS on a Ferroli F30.
Reason... the boiler keeps dropping the burners out after running for 10-20 seconds but if you bypass the APS then ithe burners stay lit and boiler runs and appears to modulate just fine. The manual speaks of the air pressure differential (flue inlet to outlet) having to be greater then 180 pascals which I understand the reason for but how do I check this.

BTW Fan appears to be running OK and is clean, venturi clear as are the the air pressure tubes to the APS.

 

[cross thread]

fault may be flue restrictor ring ,try taking it out

 

[Hoffers]

Thanks gordongas... boiler has been installed for 3 years and has no restrictor ring due to flue length and has operated OK until the last few days. Is there any way to test pressure differential without an electric manometer ?

 

[cross thread]

no.try removing the fan and cleaning the blades. also have had condensation in the a/pressure tubes

 

[Hoffers]

Ok will strip fan out tomorrow and check tubes and let you know the outcome.
If there are no restrictions in flue and tubes and the fan runs up OK then can I assume the APS has gone out of cal and needs replacement or do I need to get hold of a electronic manometer first ?

Like I say if the APS is temporally byepassed it all seems to work OK.

 

[ChrisR]

No, Ferrolis are fussy- more to it than usual. Suggest a boilawallah.

 

[Hoffers]

ChrisR, Yeah so it seems... fix one problem and find another 3 ....
is there anything unusual that you have to watch when removing/refitting the fan like seals etc or is there any seal that could be disturbed/damaged causing an incorrect pressure differential that would trip the APS.
As soon as the APS trips it resets its self and burners fire up again within a couple of seconds.... runs for anything from 5 to 30 seconds and drops out again and repeats this cycle.

Frustration or what !!!

 

[asc]

You might find a spare venturi handy, I'm surprised it's not broken yet, they are almost like an anti handling device. I seem to remember the APS on these is adjustable, so if after cleaning the fan, tubes and venturi, if it still fails you could try a small tweak.
I'm puzzled as to how it works with the APS bridged out. I would have thought the board would need to see it open circuit before the fan starts and the closed when the fan runs, to prove it is working. If this is not the case do not adjust it without a suitable digital manometer so you can see the signal it is operating from.
Let us know how you get on.

 

[ollski]

Doe it work any better when you have the combustion cover off? (as a speedy test only of course)

 

[Hoffers]

Thanks ASC... I can only assume the venturi is holding up as the boiler is only about 3 years old and has not become too brittle yet.
As for the operation of the ASP, I believe that its the fan running is what creates the pressure differential and operates (closes) the APS micro switch. I have only bridged out the switch once the burners have ignited to asses wether it was this switch dropping out that caused the burners to shut down.... thus you are probably correct is stating the board needs to see an open APS circuit before the fan starts and closed APS when the fan runs... and this is certanly what the circuit shows assuming it is drawn correctly and in its 'off/standby' state .

Sequence I guess is DWH or CH demand, fan started, pressure differential generated, APS closes, burners ignited and regulated via feedback from flow stats etc ... and APS 'should' remain closed untill the fan is turned off.

It's finding out why its dropping out that is doing my head in !!


I have not removed the APS as I do not want to end up with a kit of parts falling through my fingures when that decides to fall to pieces so I'm not sure if its adjustable and would rather adjust it knowing I have correct pressure differential to start with, but will look closely to see if the micro switch on the back of it is correctly positioned.

 

[Hoffers]

Olski,
I have not yet tried that, I assume that would indicate a flue (air in) restriction. ?? I hope not as that may mean a trip on the roof !!! don't you just love doing that !!

 

[Hoffers]

I removed fan... it was spotless checked venturi and tubes they too were spotless, checked operation of APS by gently blowing/sucking down pipes and it operated as it should (no way of knowing at what pressure though).
Refitted everything ensuring flue to fan seal seated correctly and fired up the boiler with Room sealed cover removed... everything worked as it should and APS did not drop out...
Next I refitted RS cover ensuring good seal and fired up the boiler again, once again everything worked as it should and APS did not drop the burners out.

It has now been working without problem for 3 days so I can only assume that during the investigation I either dislodged some blockage although I took great care to notice anything or the seals had not been seated corectly which they are now as when the RS cover was refitted you could hear the seal being made.

Looks like one of those endings that unfortunately can not be explained.

Thanks to all who contributed with advise and I hope this thread helps others with this boiler.


AGS....
You were right the APS does have adjustment on it although I did not mess with it for obvious reasons as I have no electronic manometer handy to check correct adjustment.


Thanks Again... Hoffers

 

[Paul Barker]

You can't really adjust it safely even with an electronic manometer without first knowing within what amount of time it must trigger at what pressure. Lazy fans will still triger an aps in the fullness of time, depends on the boiler whether pcb will have sufficient patience to wait for this to happen.

The fact that yours drops out after being triggered would point me to a faulty aps or another system fault you haven't considered like dry joint or poor spade connector contact or poor wiring loom.

This may not yet be over. In the absense if fga and digital manometer I would at the very least arm myself with a new aps.

 

[Hoffers]

Paul,
Not sure they are set up that closely tolerance to start with, there is indeed a pressure threshold it should switch at (180 pascals)and as soon as that triggers and goes o/c the burners drop out (no timer involved on drop out). Although I can't see the manufacturers calibrating every boiler around each APS and specific fan or their instructions for changing them would be a little more complex added with the effect the variability of flue back pressure has on fan efficiency which is largely dependant on flue length, restrictors being used etc, and not forgetting the pressure difference is all measured within the fan housing using the air flow through a venturi method causing one side of the APS to vacuum..
I guess what I'm saying is whilst there is a calibration window I think it needs to be quite large due to all the normal operating variabilities there are between fans and installations that you may be giving a little more credit than deserved to the manufacturers for what is a basic simply but effective safety system.

I am happy to be corrected as I'm always willing to listen and learn.

 

[Slugbabydotcom]

The fact that yours drops out after being triggered would point me to a faulty aps or another system fault you haven't considered like dry joint or poor spade connector contact or poor wiring loom.

A holed diaphragm in the APS could cause it but I would be suspecting a thermistor problem first.