Water ingress in aps tubes

[mario500]

Vaillant Turbomax 824 plus

First visit - changed aps all ok. The aps on this boiler clicks into position from the top right hand side - at the back of the appliance. It comes with new air tubes - one clear and one blue, presumably for easy identification - they enter the boiler casing through a grommet and connect to the fan via spigots. The aps has been slightly modified for this boiler, but I can't see any link to the problem I encountered.
A couple of days later customer rang saying they have intermitant dhw. On closer inspection there were drops of water in the positive air tube, (clear one). This was causing the boiler to cycle - not really noticable on heating side, but problem on dwh.
once cleared of water all ok again... A few days later the fault repeated itself! The flue termination, angle, pitch etc are all ok - no leaking gutters or anything like that. everything is completely dry inside.
Has anybody else encountered this phernonomen?

Thanks
Mario

 

[cross thread]

had it once only fault i could find was the restrictor ring was incorrect, never got called back so i either fixed it or got lucky

 

[mario500]

Cheers Gordon,

Well I know for sure that the restictor in this boiler is correct. I actually took the whole flue apart and checked the restrictor - hoping it was incorrect. But it was to Man insts ok.
I even said to the old guy who lives there - have you been squirting water in when each time I leave? he saw the funny side.
Very strange fault indeed.


Mario

 

[andsam]

I have had the diaphragm inside the APS splitting causing warm air to move through the tubes and condensing. Sorted it with replacing the APS.

If the tubes are not on properly it could possibly cause this ( I think )


Andy

 

[mario500]

Thanks Andy,

I thought there might be some condensing going on. But the aps is new - although I know new parts can be faulty also. Each time I have cleared water out of the tube - it has been about half way along. But there has been a little water in the aps itself. So maybe this fault is similar to the one you had too? I went for the third time on Sat morning to clear out the water, and to be honest I didn't have any answers for the customer. I guess if he rings again to say it has gone faulty - I will try a new aps.
Unless someone else comes up with a solution.

Thanks again.
Mario

 

[Agile]

Did you check the min/max gas burner pressure?

 

[mario500]

Thanks Tony,
Yes I checked the min and max burner pressure.. In fact before I checked the aps again that is what I thought was wrong, due to to constant cycling.. But they were correct.. The instant I removed the water from the aps tube the cycling stopped and the boiler fired on full rate at dhw demand. I even thought the ntc sensor on the flow might have been faulty giving the pcb an incorrect reading, but it was actuallly fine.
It is still somewhat of a mystery as to where the water has come from. I didn't think it was condensate, as I thought the temperature at that part of the boiler would much higher than the dew point. I guess time will tell if the customer rings back.
I have a feeling that he will.

Thanks again Tony
Mario

 

[Agile]

You dont say the size of house.

If you know how you can set the max CH heat output. If this were set too low then it might cause condensation when it first comes on.

I cannot exactly remember the orientation of the air connections into the APS.

Can the APS be rotated in the holder so that the air tubes enter at a diferent ( higher? ) angle?

From what I remember the air tubes routing is roughly horizontal. If so then are they fairly tight or perhaps too long so they droop? I have sometimes had to cut some off to stop condensation.

Tony

 

[mario500]

Thanks Tony,
I did think that the angle of the tubes entering the casing might possibly lead to a problem with condensation. I am sure the fault is something to do with this new aps and, or its tubes. You are quite correct in saying that they enter almost horizontally from the aps. But the aps cannot be rotated or repositioned at all. It has a plastic clip that secures into an oblong hole in the side casing of the boiler, so it is fixed in one position only. The tubes enter through the grommet and then drop down to the spiggots on the fan. I thought maybe they might be a little bit too long.
They are both approx 150mm long and it would only be possible to trim a little off them. The last time I put them back in I made sure they lay as short as possible from the fan to the grommet.

Thanks

Mario

 

[Agile]

I seem to remember that the original ( larger ) APC could be rotated to an extent within the clip.

I dont remember about the replacement though.

Tony

 

[ChrisR]

You can check for aps leak with a digi manometer. Pressure rises a bit as you push a short length of hose on.

A Transco chap was telling once how some gas supplies bubble through sumps in leaky pipes so carry water vapour with them. They learn where they are and have to pump them out every so often. Might be worth a call to their inquiry number.

 

[mario500]

Thanks fella's,

Update : gut rang today (wednesday) to say that the problem was back again almost as soon as I left!! but he didn't want to mither me at the time..
So I will be going back tomorrow to have, yet, another look.

Tony - the house is a bungalow with seven rads. On this particular model - setting the CH burner pressure is fairly staight forward. Low burner pressure, or if I remenber what the M inst call ignition rate, is a reading taken with the modureg unplugged. High pressure is with the modureg plugged back in. If I remember rightly the boiler is put into an engineer mode P1. and then the pressure readings taken.
One thing I did find strange - that has just come back to me, is that when I took a working pressure reading at the gas valve inlet it was quite low. Yet the gas meter is only about anout 900 mm away - in fact directly below. When I spoke to Vaillant tech they said that if the boiler is on full gas rate (engineers mode), it will affect the inlet gas pressure!! I though that was a strange thing to say!

What I can't understand is that the only thing that has been changed on this boiler is the aps and its tube! why should this condensation problem start now?

Any pointers in the right direction greatly appreciated!!

Mario

 

[Gasguru]

Heat exchanger leaking?

 

[mario500]

Thanks Gasguru,

No the heat X is fine.. everything nice and dry around that area..


Mario

 

[croydoncorgi]

How about condensation in the flue running back into the fan casing and from there into the lower of the two APS tube spigots?
If the flue is tilted UP (WRONG!) this could be it.
There should be NO airflow as such through the tubes - they just transfer pressure. If it's a new APS, there's no leak in the diaphragm so definitely no flow.