Ferroli APS

[Paul Barker]

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.

No, what I am saying is that it shouldn't be adjusted without axess to fga to check boiler performance which would indicate condition of fan at the specific flue conditions on the day, which as you describe plays a part. Because as you have said there is a largish window of tollerance (which was my main point) so to fiddle with it may push boiler into a range of performance outside manufacturers goals. Such adjustment would always be towards alowing it to trigger with less effort.

Yes thermister or holed diaphragm, wish I'd thought of that.

 

[Hoffers]

So I think we are agreed on that then, and like my previous post states I was not going to fiddle with the APS adjustment as I did not have the correct equipment to hand, and like I think what your saying is that any adjustment using correct equipment should be made as to trigger (go o/c) the APS more easily as this reflects a more efficient fan. (which in real terms is more effort from the fan required to hold it closed and burners lit).

Note:
FGA will give overall flue efficiency and content data but not APS trigger point relative to pressure which is the Manu's spec (180 pascals).

I think we can rule out a holed diaphram as per my previous post the boiler is still working correctly since Friday's strip down (where I change no parts or settings), in addition and inline with my first thoughts thermistors were both replaced (DHW + CH) before investigating anything else due to their unreliability, but were not the cause although I am getting far better modulation as a result.... sorry should have stated that earlier.


Regards... Hoffers

 

[Paul Barker]

and like I think what your saying is that any adjustment using correct equipment should be made as to trigger (go o/c) the APS more easily

No that's not what I said.

Effectively I am saying don't adjust it at all, if it's faulty renew it.

What I referred to above which you have taken as my advice was that were you without suitable equipment to alter the threshold of the aps you would only want to do so because the fan is not triggering it so you would be adjusting it to trigger at a lower seting. That doesn't mean I am suggesting you do that, it means I am saying don't do it.

Now to what I would do. I would check that the fan is doing it's job with the digi manometer and the fga, if it is doing it's job and the aps isn't triggering I would after checking sensing tubes and flue ways an venturi if it is a boiler that senses through a venturi, fit a new aps. After all they are only £10 to £20 depending on boiler.

 

[Hoffers]

Hi Paul,
All getting a bit confusing now.... I do not intend to adjust the APS and had not taken that as your advice either.

It is all working OK now, and would not adjust it anyway without all the correct equipment for the reasons you state, and on the grounds an APS is unlikely just to go out of cal without some physical deteriation in it somewhere (i.e its knackered) there would seem little point, far more likely to be something else as the APS was triggering too soon after firing up the burners... so gave the impression it had become too sensative and of cause the fan, venturi or tubes etc could have been the issue.... who knows now.


Regards... Hoffers