Worcester Bosch Boiler Pressure Problems

Discussion in 'Plumbers' Talk' started by jsaipe, Dec 7, 2013.

  1. Nope.

    The only thing I was going to suggest was a larger exp vessel, but they've done that. The reason I was going to suggest this is because a running pressure of 2 bar is really too high, and is not too far from possibly opening the safety release valve. Certainly uncomfortably high, so that's something I'd like sorted regardless of anything else.

    Since they fitted the larger exp vessel, has there been any improvement in the 'hot' pressure - ie has it become a bit lower, or is it still 2 bar?

    Anyhoo, one thing I'd like to determine - is there any water being lost out the safety discharge pipe? That should help to identify the cause of the lost pressure.

    Wrap a small clear poly bag around the pipe outlet using a rubber band or similar, and keep an eye on it.
  2. That fact that the pressure drops suddenly after a certain time doesn't necessarily mean that's when the pressure is being lost. Ie, it's not necessarily fine, fine, fine, fine, oops - lost water.

    It could be that the exp vessel is doing its job - maintaining the pressure even when system water is being lost slowly; ie the vessel compensates for the gradual loss of system water, until it can no longer do so.

    Of course, it could also be that it's all fine for a goodly time, and then the hot pressure goes a wee bit higher than usual and then it does dump the system water in one fell swoop out the discharge pipe.

    That's why you need to monitor this pipe each day until the system next needs topping up. It should be a good pointer as to what's going on.
  3. Carole farmer

    Carole farmer New Member

    We have a Worcester bosch combi, the outlet pipe was dripping, so we had a new pressure relief valve fitted, after only a few days the outlet pipe was dripping again. When the young plumber fitted the new valve, with help from the technical team at Worcester bosch, he said he thought the pressure gauge was faulty. I have contacted him he now says he needs to fit a new gauge so he can investigate what the problem is. Any ideas if this is right, seems a bit much we've got to pay for a new part just for him to investigate. Any ideas would be appreciated
  4. First, please - oh gawd, pleeeeeeex start a new thread.

    Second - if the young plumber required the assistance of the WB help team to replace a simple component like the 'blow off' valve, then I'm worried.

    But perhaps he was asking about something else?

    Do you know if he checked the expansion vessel? Did he place a pressure gauge - a bit like a car tyre type - on a car-type-like valve? Did he press that car-tyre-type valve to see if air or water came out? Did he bring out a pump - possibly like a bike-tyre type - and pump this thing up with air?

    The pressure release valve isn't something that usually 'fails' as such; it is usually chust doing its job. And that is to release excess pressure before it blows everything else upski.

    So tha fact that it's dripping again doesn't mean it's the PRV itself that's faulty, but that the original fault was likely not solved.

    So, if it 'leaks' you don't chust replace it, but you also need to find out why the pressure went high in the first place. And that is usually a problem with the expansion vessel - it either needs recharging with air (quick and cheap and easy) or else replacing (not so quick and quite easy and it'll cost £100-200).


    Only then can we advise as to whether the original guy was an idiot, or whether your gauge is faulty, or anyfink else.
    Carole farmer likes this.
  5. Carole farmer

    Carole farmer New Member

    Firstly let me thank you for the reply.

    The call to the web team was about the pressure relief valve as he didn't know all the thing had to be stripped before he could replace it.
    After putting on the new part he told me he put pressure thing on it and it was fine, that's when he said he thought the pressure gauge was faulty because the pressure was fine.

    The pressure is fluctuating from zero, to just in the green, however the heating is still working etc.

    But the plumber like I said says we need a new gauge so he can then look at the underlying problem, but I've read it could be diaphragm etc.

  6. Carole farmer

    Carole farmer New Member

    When the outlet was leaking the gauge said zero, I re pressurised the boiler, the outlet was dripping a lot, however the radiators were then making loads of water notice so I preesed the relief valve repressuresed it and bleed the rads, when we turn heating off the gauge goes to zero but when on its just in green
  7. Hmmmm...

    The system makes an 'airy' noise when you've re-pressurised it, and you also need to bleed the rads? Where is that air coming from? Not from the fresh water you add - that would only be a tiny bit of dissolved air.

    So, I suspect your expansion vessel is shot. The fluctuating pressure indicates a faulty vessel, and the fact you are getting air in your system (I suspect from a punctured vessel diaphragm) suggests it's faulty in a permanent way...

    Solutions are to replace it - circa £100 + labour - or else buy and fit an external vessel which can be plumbed in elsewhere in your system if you have a suitable location. Cost circa £60 + less labour.

    That's only a best guess, of course. (I suspect your actual gauge is fine - and your plumber is a twit...)
  8. Carole farmer

    Carole farmer New Member

  9. Carole farmer

    Carole farmer New Member

    Thanks so much for your reply, seeing we have just paid out £80 for the prv, could this wait a few weeks to be replaced or could more damage be done by waiting
  10. No real damage should be done - if the pressure falls too low, the boiler chust stops working. If it goes too high, the PRV opens and dumps the excess.

    But, it isn't ideal...

    A nifty temporary solution I've read on here is choose a convenient radiator, shut off both valves fully (always, with the 'lockshield' valve end, note exactly how far open it was first, so you can return it to that same position afterwards...). Then place a low pan or similar under one of the valves and undo the large but which joins the valve to the rad.

    Allow around a quarter to half the radiator to drain - you can either let it go glug-glug-glug or else you can open the bleed screw to let air in. No idea how much water 1/2 is, but I'd certainly let it drain 3-odd litres, I think. Don't let it empty, tho' - if that happens, you need to partially refill it.

    Anyways, once around half is drained, redo that connection and open both valves to where they were before.

    There you have it - instant expansion vessel :)

    Refill the system water pressure to 1 bar cold, no more.
  11. James Shepherd

    James Shepherd New Member

    Guys,again a problem occurred with the Worcester boiler.Here it goes;I have installed a Worcester boiler 42CDi in my house.It is being installed by a renowned company named as HVAC repair Brooklyn.The problem is,whenever I turned on the boiler a blast sound appears within boiler and also the water is not heating rapidly as earlier it was working.So,when I ask for help at company they told me to replace the boiler and for me,it is not possible to replace a boiler now.Any suggestions,how can I repair my boiler.Because the company told that the boiler's internal pot is damaged and it cannot be repaired.
  12. James Shepherd

    James Shepherd New Member

    As I am a new member,I hope you will help me with my problem .If you want I can post the photos also of my boiler.
  13. Dave does Gas

    Dave does Gas Screwfix Select

    James, it sounds as though you are posting from America. We are all UK based therefore you appliance most likely won't be one that any of us will be familiar with.
  14. And in any case your post doesn't make sense...

    It starts: "Guys,again a problem occurred with the Worcester boiler. Here it goes; I have installed a Worcester boiler 42CDi in my house. It is being installed by a renowned company named..."

    I don't understand.

    And what's an 'internal pot'?

    Seriously, tho', if it's going 'blast' inside, there's no way we can lead you through a repair from here - you will likely end up having a bad time...

    Best call out another couple of co's for their opinions.
  15. Gordon Potter

    Gordon Potter New Member

    Hi, I've got a Worcester Green Star HE30 with a pressure loss problem thats getting worse.
    About 2yrs ago i noticed i had to top up the system every 3 mnths or so. This has now become every 2-3 wks even with the heating off. No air in the rads and no drips outside. The service tech said it's a leak in the h/w pipe work but no obvious signs. Could it be the pressure vessel.
  16. itchyspanner

    itchyspanner Member

    does the boiler need a service soon?

    If so ask your engineer to check the expansion vessel is ok and set correctly when the service is done.

    you can do this:

    with the power off set the pressure to 2 bar at cold and turn off the heating isolation valves under the boiler and put a bag or tub under the discharge pipe outside.

    leave the thing alone for as long as you can and see if the pressure drops, do the same test with the isolation valves open. You should then know if the drop is boiler or system related, if the prv is passing. If the isolated boiler drops but no water comes out of the discharge then its prob going down the condense waste. Tell your engineer anything you find from this test. If the drop is on the system then you have a leak on the heating system. Most common leaks are on rad valves and system componets. check these, if no joy hire a thermal camera and look for damp/cold spots where pipes run.

    please note that only a GSR can remove the cover of this boiler as the case forms part of the combustion system as is classed as gas work.
  17. Gordon Potter

    Gordon Potter New Member

    Thanks for the info. Will have to wait until we go away for a few days before trying as it's our only source of hot water.
  18. Dave does Gas

    Dave does Gas Screwfix Select

    Mod's please lock this thread and let people start a new one this ones getting silly
  19. Ian Chipp

    Ian Chipp New Member

    A marvellous explanation of these pressure faults - many thanks Devil's Advocate - it has helped me understand the fault on my own system. I am a novice on these pressurised systems, done a couple a traditional system installs, the new stuff can be baffling though !. The E.V must be faulty on my system, large swings in system pressure cold to hot. I have to top it all up every week to, so must be a leak via the PRV or even out of the EV.

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