Vaillant Ecotec - air in the system

[JSault]

Hi,

I am wondering if anyone can help me with our boiler problems.

We had a Vaillant Ecotec Plus 428 installed last August to an open vented system. We have had a succession of problems from day 1 and Vaillant have been out twice.

Our latest problem is that when both the heating and water is on together, we get a lot of air building up in the system which is turning the water dirty and the boiler then cuts out (S23 error code). I have had to bleed the radiators twice a day so keep them warm and clean the Fernox filter every couple of days.

I have noticed that when both HW and heating on, there are bubbles in the header tank in the loft and a whooshing sound as the air collects. But if I have the HW and heating on separately, there are no bubbles, no whooshing sounds and no air build up in the radiators.

My installers response was that there is a leak in the system and we should have a closed vent system but if that is the case, then why does it only occur when both HW and heating are on together? I could get the system flushed again (as advised by Vaillant) but I don't see any point in doing this until we work out where the air is coming from.

Obviously I now never have the HW and heating on together but its not ideal. If anyone has any ideas, it would be much appreciated.

Thank you
Jane

 

[lightning]

What speed is the pump on??
How is the cold feed arranged ???
High high is the vent over the f[e tank.

sounds like its drawing in air through the vent pipe.
you can always check for a leak by tying up the ball valve and see if water level drops.

 

[ScottishGasMan]

On an open vented system its perfectly possible to have a small leak which when the pump is on draws air into the system, however as pointed out, this is unlikely to be the case when only happening with both on.

As above, would be handy to know how the Cold Feed/Vent/Pump/Bypass are set up? The likelihood is that the system is drawing air in through the open vent.

Being a heat only boiler, the boiler relies on your system being setup and installed correctly to move the water and heat efficiently out of the boiler, thus why you will get faults when this is not happening.

 

[JSault]

Many thanks for responding.

The pump is a new one (Grundfos) and is on the highest speed setting. The installation of the new pump does tend to coincide with the start of the air problems though?

I will test for a possible leak and revert.

Jane

 

[ScottishGasMan]

Many thanks for responding.

The pump is a new one (Grundfos) and is on the highest speed setting. The installation of the new pump does tend to coincide with the start of the air problems though?

I will test for a possible leak and revert.

Jane

Would be handy to give us info regarding the relative positions of the boiler/pump/vent/feed pipes

 

[JSault]

I will answer your questions as best as I can but apologise in advance for my complete lack of knowledge as regards plumbing. Our installer/plumber is not interested in sorting this out so I am in the dark.

The boiler is on the ground floor. The hot water tank is located in the airing cupboard on the first floor along with the pump. In the loft above, there is a cold water tank and a header tank.

When you ask for the height of the vent over the tank, which tank should I be looking at? Is the vent the pipe over it?

Jane

 

[ScottishGasMan]

It will be the small tank in question and the vent will be the pipe above it,

from the small tank, there will most likely be 2 pipes, a thick one (22mm) and a thinner one (15mm) these (probably) feed down to either the cylinder or the boiler. It would be handy to see a photo of the cylinder/pipework if you have time.

Also, worth sticking the heating and hot water on at the same time, and have a look at tank in loft and see if water is pumping over the vent pipe.

Almost certainly you will need another plumber/heating engineer to sort the problem right out, (and then flush the system) but we can try advise a little on here.

 

[ScottishGasMan]

from the small tank, there will most likely be 2 pipes, a thick one (22mm) and a thinner one (15mm) these (probably) feed down to either the cylinder or the boiler. It would be handy to see a photo of the cylinder/pipework if you have time

Actaully should say 3 pipes, one thick (vent above) one thin near the base of the tank - this will be feeding water into the heating system and a 3rd small pipe this will be the mains feed to the ballcock in the tank (also possibly a 4th plastic over flow pipe) the position of the overflow and the pipe feeding the ballcock arnt really relevant here

 

[JSault]

Yes there are 3 pipes. The thick one (vent) drapes over into the tank (almost touching the side) the bottom end is sitting about 10cm above the water level. There is no water coming over this pipe when the HW and heating both on. The thin one near the base of the tank is where the air bubbles are coming from and I can see water circulating around the opening. I would have said a leak here but then why does it only occur when both HW and heating is on?

Thanks, Jane