Vaillant VCW 242E Issues

[rwalters]

Hello guys,

We have a Vaillant VCW242E boiler, about 16 years old I believe. We have had over the last year pressure drops of about 1bar over a period of 1-2 weeks. We have to keep topping the system up.

I have also noticed a strange issue over the last couple of months, doesn't happen always, but only sometimes. When we are filling a bath or taking shower, the temperature guage on the front of the boiler rises to about 80 degrees and the pressure goes up to about 2bar.

When I see this has happened, I open a hot water tap, the boiler makes several loud gurgling noises for about 10 seconds and then the pressure and temperate start to drop to normal again.

I have checked all radiators and pipework that I can see and no leakage there. I cannot check under the upstairs floors, but after a year of this happening I would have thought I would have started to see some sign of staining on the downstairs ceilings. The overflow pipe is not leaking, I have put the finger off a rubber glove over it for a week and it is bone dry when I take it off again. The boiler itself is dry as far as I can see, I have taken the front and side covers off and had a good look inside and it is dry.

Any ideas ?

 

[DP]

It is time you call someone in. Ensure he knows this boiler (a lot of so called engineers do not- they will recomend a new boiler).

Goo boiler worth repairing as it will keep on working.

I getthe feeling the boiler has not been serviced for a while.

You location would also help.

 

[Gasguru]

Have a look for leaks on the auto air vent (down the back of the boiler on the right hand side).

Also see if you have the black plastic secondary heat exchanger (look underneath on the left) - notorious for leaks.

 

[rwalters]

Thanks for the replies guys. We live in Lincolnshire. We have British Gas cover on the boiler, so maybe we need to call them out to it, I am just a bit worried that the leak may be underneath on of the floors downstair.

The heat exchanger was replaced about 9 months ago, I have checked all the joints around it (4 in total) and they are all clean. As for the auto air vent, I am presuming you mean the bit on the right ?? that has the valve on the top of it, if so, this is also clean and no signs of leaks.

We have the boiler serviced every year by British Gas, not sure what they do, they just twiddle for a while and give us a report.

Anymore helpful info greatly appreciated.

 

[weareleeds]

Have you taken plastic heads off of the rad valves to feel the spindles for slight dampness old valves are notorios for leaking you could also get B.G. to add some leak sealer to system

 

[rwalters]

I have taken the rad controls off and had a good look at the valves themselves and they all look ok, the only one that has leaked in the past is the one if the downstairs toilet, it is a but furry looking, but it is dry. I have added some leak sealer to the system myself, Fernox Leak Sealer, but didn't make any difference at all.

 

[rwalters]

Anyone else with any ideas before I put a call into British Gas and get them to rip the house apart

 

[ChrisR]

Good luck looking - can be a difficult problem. I am looking at a 3 year old system with a similar story, so don't be persuaded that it's the boiler's fault.

Sllightly less uselessly:

As for the auto air vent, I am presuming you mean the bit on the right ?? that has the valve on the top of it, if so, this is also clean and no signs of leaks.

Yes, high up.
The cap on this has to be left undone a couple of turns, to let air out.
Worth replacing an old one "on spec" because any leak here tends to evaporate before it's noticed.

 

[rwalters]

Just another clue that might help, we get a lot of air into the system upstairs, mainly in the towel radiators in the bathrooms. Not sure if that helps anyone, but thought I would throw it in anyway.

 

[ChrisR]

Ah, WELL.
You may have a micro-leak - one which lets air in but not water out, but you would expect the air to collect in just one radiator.

Corrosion produces hydrogen. You can (carefully) light it when bleeding a radiator to prove its presence.
Any gas should get out through the auto air vent. Bleeding the rads will also drop the system pressure.

Suggest you try putting some corrosion inhibitor in. There are syringe types which you can "inject" through the filling loop.

 

[rwalters]

Would air getting into the system or hydrogen being produced in the system by corrision cause the pressure to drop on the boiler ?

We have the system drained and refilled about a year ago as we had the upstair rads changed, corrosion inhibitor was put in at that time, but I think as I am having to top the system back up constantly, it has probably all gone now.