Boiler won't hold pressure

Discussion in 'Plumbers' Talk' started by blertsville, Mar 6, 2015.

  1. blertsville

    blertsville Member

    Worcester 42 cdi boiler ,pressure drops constantly and runs out the condense pipe when boiler is on the water is hot , the expansion vessel is up to 1 bar,the pressure release valve is fine any ideas
     
  2. Dave does Gas

    Dave does Gas Screwfix Select

    Sounds like your heat exchanger has gone, Give Worcester a call as there is a ten year warranty on their heat exchangers, think you'll pay for labour only
     
  3. Ooh, I have one...

    http://community.screwfix.com/threads/green-star-24i-no-pressure.156507/

    If the water runs out the condensate pipe, then the source is almost certainly from within the combustion chamber.

    So, heat exchanger? Joints, pipes etc from in there?

    I'd recommend you call out a W-B approved engineer to look at it, as very good chance you can claim for a new one.
     
  4. Pffft - as Dave says :)
     
  5. plumber-boy

    plumber-boy Well-Known Member

    Not another one.:)
     
  6. What is it with W-B exchangers? Dropping like flies.
     
  7. plumber-boy

    plumber-boy Well-Known Member

    I've got a WB.:( 1425669523795.jpeg
     
  8. blertsville

    blertsville Member

    Thank you spot on , a good reply unlike the others , thanks again
     
  9. plumber-boy

    plumber-boy Well-Known Member

    Your welcome.:):)
     
  10. I think you'll find my reply was chust as accurate and more comprehensive - via a link to a 3-page thread.

    You chust couldn't be ar*** reading it all. Typical yoof.
     
    itchyspanner likes this.
  11. Dave does Gas

    Dave does Gas Screwfix Select

    Its fairly common unlike the Vailliant stainless steel heat exchanger, Having said that if you dry fire a valiant its a new heat exchanger needed.
     
  12. I guess giving a component a 10-year warranty can be for two reasons - one is that you have genuine confidence in the item, and t'other is that you have to give the confidence to the buyer...

    What are the W-B exchangers made of? And where do they fail - is it at a seam or summat?
     
  13. Glad its Friday

    Glad its Friday Active Member

    Worcester h/e made of aluminium. Worcester will try hard to get out of honouring their warranty unfortunately, so make sure that the boiler service record is completed and bang up to date before calling them in.......

    Vaillant h/e have a built in thermal fuse, when that blows as Dave says is new exchanger time. Never press the reset button more than 3x on a Vaillant for that reason.
     
  14. KIAB

    KIAB Super Member

    Vailliant here...
    [​IMG]

    Glad I didn't go WB, aluminium heat exchanger put me off.
     
  15. plumber-boy

    plumber-boy Well-Known Member

    Blooooooody show off.:)
     
  16. Glad its Friday

    Glad its Friday Active Member

    Vaillant here as well.
    Whenever I service a boiler with an aluminium h/e, in the condensate trap there are always deposits of aluminium presumably dissolved off the exchanger by the acidic condensate. Must mean that the exchanger is rotting out from the inside? So Stainless exchangers for me.
     
  17. Dave does Gas

    Dave does Gas Screwfix Select


    Thats true the amount of greasy messy aluminium deposits that come out of the worcesters comdensate trap is startling
     
  18. The irony - why do peeps choose aluminium for when they need a non-corroding metal? 'Cos it's akshully one of the most reactive metals oot there.

    I well remember an experiment from my secondary school days, one that wouldn't be repeated these days - 'cos it used mercury.

    A piece of 'luminium metal plate - which looked in well good order - was pushed under the surface of a pool of mercury, and scratched with a sharp scriber. Our chemistry teach then took out the 'inium plate and sat it on the bench. We watched - gobsmacked - as 'fur' grew out of the scratched shape before our eyes; the aluminium was corroding visibly - in seconds - in front of us.

    (The mercury got into the scratch and somehow prevented the aluminium oxide layer from forming over the scratch an protecting it from further corrosion. It is the tough corrosion (aluminium oxide) layer that forms a skin and prevents further corrosion! Hence 'anodising' - which forcibly forms an even thicker oxide layer. And that's why they don't allow mercury-filled thingies on to planes...)
     
  19. itchyspanner

    itchyspanner Member

    alu has good thermal conducting properties and good manufacturuing properties. in general it has good corrosive properties in general
     
  20. It has lots of great properties to be sure to be sure, but it is actually a very reactive metal - it'll oxidise in seconds if allowed to. The 'rony is, this layer of aluminium oxide is so hard and tough that is actually seals the aluminium and prevents further corrosion. So we have a very reactive metal sitting safely inside a skin of its own oxide.

    Anything that breaches that oxide layer and prevents it from 'skinning' will render the aluminium - like wot the mercury somehow did. The aluminium then corroded before our eyes.
     

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