Vaillant VCW 242 pressure loss

[sbothwell]

Hi,

having some trouble with my Vaillant VCW 242 EH losing pressure in the CH part, needing topped up about once a week at the moment. I top it up to about 1.5 bar, then the CH runs and the pressure goes up to the max while the CH is running. Once the CH stops and the system cools down the pressure has dropped a little, until after 5 or 6 days its under the 1 bar line and I have to top it up (although it appears to run fine if I don't notice its gone under the MIN line).

I've done some reading about, and I think it might be the expansion vessel needing re-pressurised - does this sound right? If so, there is a red tank at the back of the boiler which i presume is the expansion vessel, and at the top right hand side of the boiler (but not obviously a part of the red tank) there is a small chamber with what looks like a car valve in the top of it, with a cap with a hole in it on the valve, and the cap isn't screwed down tightly. Is this the valve i need to re-pressurise the expansion vessel from, or is there one actually on the vessel itself?

Any advice appreciated.

 

[greemyamochop]

Have you checked the discharge pipework? It should be the copper one outside, check it to see if theres any sign of water coming from it.

Obviously to lose pressure the water is going somewhere so try that first mate, just try checking your rad valves for small weeps etc too

 

[Peruse]

It points to your expansion vessel low on pressure and yes it is the red vessel. The other part on the right you have pointed to is your auto air valve.

If you look in the FAQ you will find a question on the expansion vessel by chrisr you need to read that.

 

[sbothwell]

Thanks guys, and ChrisR, re-pressurised the expansion vessel and it seems to be working much better now - a lot quieter as well.

However, noticed another small problem when testing after re-pressurising and re-filling the system. There is a round black fitting in the middle of the boiler which has a number of small pipes going into it, and there is a very slow drip coming from what looks like a spindle on the back of this. I never noticed it before because it drips down onto the dish drainer but i saw the splash marks when i'd cleared everything to work on the expansion vessel.

Any idea whats likely to have caused this, and is it fixable or do i need an engineer? (There is another black fitting which has a microswitch attached to it - its not that one that is leaking but the one above and slightly to the left).

Cheers.

 

[Bunnyman]

This is called the p/d valve part 151017 drain boiler to fit

Untitled

• Bunnyman
• 26 Mar 2010
• 499