losing pressure on combi boiler

Discussion in 'Plumbing and Central Heating' started by peted, 5 Jan 2004.

  1. peted

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    I have a worcester 240 combi RSF boiler. Over the last few months i was having to top up the pressure manually with the tap on the silver braided pipe, about once a week to keep it at 1.5 bar. Now that its colder and the boiler is being used constantly the pressure is dropping down to 0 bar every 2-3 hours. I've checked for leaks on the rads and found none. I have noticed a small drip of water on the bottom grill of the boiler casing sometimes but can't see where its coming from. Also there is a bent copper pipe coming out of the wall directly behind the boiler and it drips constantly (is this the pressure relief pipe?). Its dripping cold water though, would that still be from the boiler? would this amount of pressure loss definitely be a huge amount of water or could a drip cause it??
     
  2. BelgraveHeating

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    Yes the pipe is probably the pressure releif and yes if it is a constant drip it could cause the huge pressure drop.
     
  3. breezer

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    its only a thought, but the "drip" may be whats left after it emptied itself and now perhaps its (the pressure relief valve) not closing propely.

    thats what my boiler did (not same as yours but it is how it lost its pressure)
     
  4. stonky

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    The problem you have is a simple one to cure. All you have to do is replace the expansion vessel in the combi boiler.I had the same problem with my worchester combi,the system would lose pressure every month, then every week, eventually every 3-4 hours.When I topped up the system to start it (1bar),the pressure would increase to 3 bar and drain through the relief valve and this would cause the boiler to fall below the 0.5 bar required to keep the system working.After a few replies from my queries on this forum the first step was to check if i could increase the pressure in the expansion vessel (large red tank in boiler) .There is a small valve that looks like what you would find on a tyre. if you can increase the pressure with a foot pump to 1bar you may have solved the problem,but I,am sure you will find that it is full of water and will have to be replaced as the rubber flange is burst.(part around £50) I replaced my expansion vessel 4 weeks ago and the system only fluctuates between 1 bar and 1.8bar.(hope this helps)
     
  5. peted

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    Hi, i actually found out today that the pipe i was talking about won't be the pressure relief pipe. I was talking to a boiler service engineer and he said that because its just a 15mm pipe it will be the condensation overflow or something. But ive just had a closer inspection and found a drip coming from a H piece, which is joining the two 22mm inlet and outlet central heating pipes. The H piece joins the two together and has a screw in the middle, with a cir-clip, this is where the drip is coming from. Does anyone know what it is. Also i found the valve on the red cylinder and pushed in the valve part and nothing came out, no air or water? Does this mean anything??
     
  6. DP

    DP

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    First of all pressure vessels do fail but not very often. Just because the pressure rises to 3bar, it does not mean that the vessel needs to be replaced. With no water in the system, gauge indicating 0 bar, the pressure should be 0.7 bar in the pressure vessel. If water comes out of the vessel valve, then replace the vessel.
     
  7. peted

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    I tested the vesel with a pressure gauge and nothing came out, no pressure or water, its as if its empty, can this happen. Also does anyone know what the H piece is i mentioned above, because i tried turning the screw and its leaking more now?
     
  8. COG

    COG

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    First things first , you have established you have pressure loss from the pressure relief pipe so need to replace the pr valve its not a condensate drain as the 240 is not a condensing boiler, when you have the system empty test your pressure vess again it should be at least 7psi you can re-pressurize using a normal hand or foot pump ,the screw you have leaking is a by pass from the flow to return ,a sod to stop dripping ,remove circlip unscrew the by pass screw (it wont want to come out without a fight )replace o ring or use thread tape and re fit. if any water comes out of the air valve on the pressure vess then you will have to replace it but about 50% just need air (thats Worcester 240 not all pressure vess )
     
  9. peted

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    Thanks for that cog. Now all i need to know is what does the pr valve look like? Is it the silver thing with the solanoid valve on it? Or is it the valve with the red knob on the end?
     
  10. COG

    COG

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    Its the valve with the red knob onit, bit of a pig to change mind, not conplicated just hard to get to ,the replacment may have a black end same part just a differant brand
     
  11. peted

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    Cheers, i'm going to leave it for tonight though. Just been fighting with that leaking screw, you werent wrong about it been hard to get out.
     

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