Water ingress in aps tubes

[Agile]

Unless the inlet pressure > 18 mB and the min/max settings are correct and ideally the max CH burner pressure then the boiler may not be operating correctly.

If the settings are incorrect then everything else may be fine. You must set it up correctly before looking for faults which may not exist.

Tony

 

[mario500]

Thanks Croydoncorgi


The flue is not tilting back towards the boiler. I got my step ladder and torch and looked from outside to see if water had leaked back along the flue.. I could see dust that had accumulated over the years and no water tracks at all.. Apart from that the general horizontal axis of the flue is correct.
Thanks for your input - it is good to know that other engineers are thinking about this one.


Mario

 

[mario500]

Thanks Tony,

Well there lies the rub! The inlet pressure was low! I seem to remember that it was very low.... I had two manometers - one on gas valve inlet and one on the meter.. there was a discepency - I think quite a lot - sorry - been to alot of jobs since so can't remember the exact amount... Like I said, Vaillant tec seem to thing that is ok when the boiler is in engineers mode? but how can it be? The only way I could get 18 mbar on inlet was to un-engage the modureg! I am confused.. I even adjusted the govenor and managed to increase inlet pressure a little.
Vaillant were not much help really - I think I commumicate quite well and don't really know why there is a misunderstanding . 18 mbar is the absolute minimum requirement! on full gas rate - am I correct with that statememt?

Mario

 

[croydoncorgi]

OK - if the flue tube is obviously dry and has been for ever, the fan casing should be too. But the water in the tube has to be coming from somewhere.

If there WAS a hole in the diaphragm of the APS there WOULD be airflow through the tubes and if the air coming into the boiler from outside was cold, it WOULD cool the tubes and any water in the flue gas in the tube would condense.....

It might be worth checking: pull the lower tube off its spigot and put the end in a glass of water. Start the fan running (and be ready to turn it off again before the water reaches the APS!). If water travels more than a couple of inches up the tube and looks like keeping going, then there's a hole in the APS diaphragm.

If there's no airflow through the tube then any water in there MUST be running (as liquid water) from the bottom of the fan casing into the end of the spigot tube.

Edit: Do you mean the INLET pressure at the gas valve goes way below 18 when the boiler is on full power??!! If so - that needs to be fixed first. In DHW mode (ie. close to full power), if the inlet pressure is too low the burner will struggle to raise the temp of the heat exchanger and exhaust temp WILL be low - maybe low enough to cause condensation inside the fan casing. With the meter that close, it sounds like there's a governor problem so that the meter fails to deliver correct pressure at high flow rates.

 

[ChrisR]

SUrely it's easier to use your manometer, even if it's a water one, to see if the aps is letting by - as above? Puff into manometer, pinch tube, connect it on to aps.

Water in a gas meter/pipe does funny things to the pressures you get...

 

[mario500]

Thanks Croydencorgi,


I think that the inlet pressure has to be a factor in this. It is very low when boiler is at full rate! I adjusted the govenor - like you do or don't do, only to get a slight increase of pressure. I find it hard to understand that this problem wasn't there before. Maybe the re-design of the aps has made this problem more apparent? or maybe like you say - not enough gas volume - not enough temperature at the heatX.

Tomorrow I will take a much closer look at gas pressures.

Thank you
Mario

 

[Agile]

We can only help you if you quantify the pressure at the meter and at the boiler inlet when on full power. Just saying its "very low" does not help us.

I went to a boiler yesterday which was stated to be very poorly fitted with dire warnings that if it was unsafe I would not proceed any further.

It turned out to be a pretty average installation. Several discrepancies but the worst was the hole around flue had not been sealed. Thats not bad for illegal Chinese builders!

Tony

 

[mario500]

Update.

Went back to job today.. Water in aps tube again...
Found the inlet pressure was only 14 mbar, yet 22 mbar at the meter.. Took the gas valve off and got a load of crud and soot out of the filter... Result of that was 21 mbar at the inlet - fantastic!!
So I reset the high and low burner pressure at the modureg in engineers mode..
All seemed ok.. Then I tried to range rate it for CH, although it is a fully modulating appliance - I wanted to make sure it wasnt set too low.. I remembered what Tony had said about the appliance starting up from cold in CH mode was probably the cause of the condensation..
To range rate this boiler, you use the contol panel - using a U gauge measuring burner pressure - you set the controls so that a programmed max range is set into the boiler and stored electronically. As you move the digits up and down, 1 - 15 you should see the burner pressure increase or decrease depending on where you set the digits to. I couldn't really get the burner pressure to go any higher than 4 mbar!!
So consequently, the guy rang at tea time to say his DHW ran cold again!

So there is another fault with this boiler! I have a feeling that it is the pcb after all.. I think that in CH mode the PCB is not sending enough voltage to the modureg.

Any comments greatly appreciated.

Mario

 

[Agile]

Now you may be getting somewhere!

THAT is the kind of thing that I had expected, the CH being too low to prevent condensation when starting up from cold!

What you found on the blocked gas input just demonstrates why I teach all my trainees to check the BASIC aspects first including gas supply pressure at the valve inlet on full power!

Dont be in too much of a rush to change the PCB. The setting procedure is fiddly and it may just be locked at the minimum CH power by somebody before getting muddled.

I suggest you go through the setting procedure exactly according to the book another time or two.

Tony

 

[mario500]

Thanks Tony,

I am going to go back to the job in an hour. So far the Dhw has stayed hot, so my visit will be to check the air pressure tubes and to have another go at adjusting the CH max burner pressure. Although I spent alot of time on this procedure last time and feel that I did it all correctly.
Sometimes when you spend alot of time at the same job it is good to come away and have a breather - I may possibly have misinterpreted the procedure.

Will post my results whether good or not so good.

Thanks again
Mario

 

[mario500]

UPDATE.

All seems fine now.. No water in the aps tubes - customer happy!!

Thanks for all those who gave input. Thanks Tony..


Mario