Condensing boiler packed up?

Discussion in 'DIY' started by vinniethemanxcat, Dec 21, 2010.

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  1. If your boiler is fairly new, it's probably a high efficiency condensing boiler.

    This involves running a plastic pipe out the wall to a drain, to carry away the condensed water, which in this severe weather is causing the pipe to freeze up, and the boiler stops working.

    If you can identify this pipe, and pour warm water along it outside, you can often free it and the boiler will work again, but often the boiler has "locked out" and you will see a flashing red light which needs resetting first..... check the user's manual.

    Had a really bad one today..... shite design, pipe about 5metres long across a flat roof, told the customer I could unfreeze it, but would be refrozen in 24 hours.

    In this case, if you're desparate, and you DEFINITELY know which is the condensate pipe, (normally white 22mm PVC), you could cut it with a junior hacksaw, and put a bucket underneath, doesn't need emptying very often, at least you'll have a warm Happy Christmas.
  2. Sympathetic_Reaction

    Sympathetic_Reaction LE Book Reviewer

    Good advice...I'll add the fault when the wind is strong and your boiler fails to start up it may just be that the pilot light has been blown out...clearing the fault (via the red button) should solve it, but I have had to do a power off reset once on mine.

  3. One caveat, it may take a bit of time for the sensor to dry out after you've cleared the blockage, so don't be too surprised if it doesn't burst into life immediately.

    I've got a blockage in the pipe at the moment but I suspect it's more than just ice as the sensor isn't draining despite the external pipe being clear. I've opened up the sensor's plug and just let it drain into a tray, emptying when required. I'm somewhat reluctant to start playing around with it whilst it's working :)
  4. Gent's, if I may tap your brains from a slightly different angle.

    I have a combi boiler that doesn't keep it's pressure - I'm having to re-charge every few days. The manual says that I should suspect a leak but there are no visible signs around the house - no leaky pipes/joints, no damp patches on ceilings/walls/carpets. The only clue, aaprt from the reduced pressure indications on the gauge, is a damp puddle outside the house below where the vent/overflow(?) pipe appears. I charge the system to what the manual says - 1.5 bar - and disconnect the flexible pipe so there is no seepage from the mains supply. Before I call British Gas (again), can you give me any clues as to what might be the problem. Being a total biff when it comes to plumbing I really don't have a clue whether it should operate that way or whether there really is a fault that needs sorting.

    Forgot to add: the only plumbers I know are the ones who hang bombs on airyplanes.
  5. Hi,
    I had the same problem where my boiler wouldnt keep pressure, called a guy out as there were no evident leaks etc.
    he recomended adding a product made by "fernox" which sealed up said leak, he did say the tiniest leak can cause a pressure drop.
    It has to be done by a heating engineer as he used a hand operated pump to get it into the system. It was done about 6 months ago and i never ever had to "top" the system up since.

    kind regards,

    R M
  6. Roger, thanks for that. I did use to have Fernox in the system when I had the old system with the header tank. The BG man said it was not serving any useful purpose in a closed system and the system was drained down when I had a sludge filter fitted back in September. I am a bit surprised that it seals leaks as I thought it was an anti-coagulant that stopped the sludge settling in various parts of the system - I might just give it a go however as I'm pi$$ed off with BG and their repeated return trips to fix faults that the previous "engineer" has created.


  7. We had the same problem last year. Inside the boiler there is a diaphragm valve, that is only supposed to operate when the water pressure is to high, it dumps the extra water through the overflow pipe.

    Our boiler is serviced by British Gas, when we called them out, the service engineer knew what the problem was straight away. It wasn't a big job either.
  8. Hi again,
    The product i think you are referinf to is fernox MB1 which is a cleaner/anti sludge additive.

    This is the badger i was on about
    Fernox Super Concentrate Internal Leak Sealer - Fernox available at Plumbworld

    Hope this helps,

    Kind regards,

    R M
  9. The pipe discharging outside is (should be) the discharge from the PRV, pressure relief valve, safety valve to you. The pipe usually goes through the wall below the boiler.

    The PRV/ safety valve opens if the pressure exceeds 2.5 or 3 bar, to avoid excessive pressure splitting a pipe or heat exchanger. It is spring loaded and should close when the pressure drops, but because there is usually so much crap in CH systems, you will sometimes get a bit of grit on the seat which stops it closing; it drips thereafter. This is a very common problem.

    You can sometimes clear the grit by turning the easing knob (or lever) to blow some water out. Usually you need a new PRV. They're usually cheap.

    The PRV usually opens because the air charge in the expansion vessel is low. It usually needs topping up with a tyre pump, to whatever the manual recommends, with the system drained; get this done when the PRV is replaced.

    Fernox and Sentinel are water treatment products. You need to put in a bottle of corrosion inhibitor when you refill the system. Don't put leak sealer in, it doesn't sound like you need it.

    " The BG man said it was not serving any useful purpose in a closed system and the system was drained down when I had a sludge filter fitted back in September."

    BG are a bunch of cants of the lowest order; they do a gas training course, think they're engineers and they know sod all about water systems. There are a few good technicians.

    You need corrosion inhibitors in the water.

    The diaphragm valve in a combi is something else, not related to this.
  10. Looks like I got my valves mixed up. To be honest I've slept since then, although I do remember the engineer saying there was a hole in the diaphragm, and the valve needed replacing. It's worked OK since then.
  11. Gents,

    Thank you very much for your informative answers. I will have to put my trust in yet another visit from BG, seeing I pay for the pleasure of there "worry-free" cover. I only hope they don't send the same clown who caused a series of 5 visits in six days in September.


    Have a cracking Christmas guys.. and if you are somewhere hot and sandy, stay safe.
  12. I had MOD Housing out to my boiler yeasterday with this very thing, the man told me it is a real big problem in our area as he has been to loads of the other houses.

    The other is burst pipes, it turns out that the lofts are to well insulated so the lofts spaces are not getting any heat from the heating, this is then leading to burst pipes.
  13. better advice than my mums friend got over xmas, rang the helpline and their answer was turn the heating off! when she explained she was 74 they said they could come out and fit a thermostat for £199 plus labour, great seeing she paid £2k for the boiler 12 months ago. well done british gas.
  14. Mine did the frozen condensate pipe, making very loud rumbling noises. My dad did the hacksaw and bucket trick and so far I've had no further problems with my cheap nasty Saunier-Duval piece of shite!