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Help needed!! Cold radiator driving me crazy!!! Argh! :-S

Discussion in 'Plumbing and Central Heating' started by s79, 24 Oct 2013.

  1. s79

    s79

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    Apologies...this is a slightly long post, but here's a quick summary to save you falling asleep:

    - Old style (30+ years old) boiler/CH system
    - Single rad in upstairs bedroom hot at the bottom/cold at top
    - Bleeding didn't work
    - Rad replaced - same problem
    - System now out of balance too!


    Long version:

    We have an old style 30+ years old boiler/CH system (NOT combi)

    There was a single panel radiator in an upstairs bedroom that was not warming up fully - warm at bottom of rad only/cold on top, although it was working ok last year i believe.

    Attempted to bleed it, but didn't even get the slightest hiss of air let alone any water dripping out. This (incorrectly?) led me to believe that the rad was on its way out.

    Initially I took rad off and flushed it with a hose, it was full of loads of black gunk, stuck it back on, manually topped up the header tank* (see below), bled the radiator plus the bleed valve in airing cupboard, but problem remained, in fact was possibly marginally worse...i.e. heat just sitting right along the bottom now.

    So took it off again and flushed it with a hose again (i know... i should have worked out that air in the system was probably the cause by then!) Put the rad back on, topped up the header tank*, bled the whole system this time - i.e. all the other radiators/airing cupboard valve, but problem remained...so then..... i fitted a whole new rad! Fully bled the whole system, but guess what - rad still cold!

    Although I did notice the new rad did actually expel air when bleeding this time.

    Anyway can I assume it wasnt the old radiator at fault right?


    Some other points worth mentioning:
    - All other rads in the house are/were fine in terms of heating up properly
    - Since starting this "work" none of the other two upstairs rads have bled water, only a little bit of air
    - *The the ball cock in the header tank(?) may be faulty as i have manually top up the tank myself
    - i dont think the system has ever been properly flushed or neither has anyone put any inhibitor in it!!
    - there is always air lock issues/low header tank level when we start using the system again every year



    This thread from 2003, and in particular the post by Paul the Plumber seems very relevant to my problem?

    http://www.diynot.com/forums/viewtopic.php?t=1388

    I have tried to follow Pauls suggestion of going round opening and the bleeding each rad at a time, this seemed to help somewhat i thought, as the problem rad was getting a fraction warmer in the top right hand side, but now all the rads upstairs are cold! I think that they are out of balance now or I've moved the air lock???

    All downstairs rads are fine however.

    So my questions are:

    1) Is/was it an air lock in the pipe work leading to this rad causing the problem?
    3) How do i get this air lock out of the system???
    4) How do i balance the system - is there a quick guide?

    p.s. anyone in Leicester able to look into this for me...its really doing my nut in now! :confused:
     
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  3. footprints

    footprints

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    Do you ever get water out of the bleed screw?
    If not the rad is not fully filling with water, and will not get hot.

    It may be you have a blockage, most common point is where the cold feed joins the system . How fast does the system fill when you have drained it?

    My guess is that the system is not filling properly from the tank and the work you have done has lowered the water level in the system stopping the other rads from working too.
     
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  4. s79

    s79

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    Hi Footprints,

    No, I never saw any water out of the bleed screw at any stage with the problem rad i.e. when the old one was flushed or with the brand new one.

    Neither of the other two upstairs rads bled water either, but they were getting hot ok previously (before i messed around).

    Apologies, im a novice really when i comes to plumbing...when you say how fast does the system fill when i have drained it, what do you mean by that exactly?

    Could it simply be case of not being enough water in the system!?!? :eek: The header tank is approx half full as it stands at the minute, but i will need to re-check it. Also the problem rad is in the same room as the hot water tank/header tank.
     
  5. footprints

    footprints

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    Yes there is not enough water in the system to fill the top rads.

    Did you just turn of the rad valves and drain the one rad into a container or put a hose on the bottom of the system and drain the whole thing?
     
  6. s79

    s79

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    Thanks again for your reply Footprints,

    I topped up the header tank with approx 9-10 litres of water just this morning following installing the new rad last night.

    Is one single rad staying cold at the top a symptom of a system not being adequately topped up? Would it not affect more than one rad? How full should the header tank be??

    When replacing the rad I closed off the valves of the radiator only and drained into a container, I did not not drain the whole system.
     
  7. footprints

    footprints

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    Just before I go thought I would add this.

    The header tank feeds the system a common point for blockage is where the pipe enters the circulating pipework.

    The black sludge stuff you found in the old rad is what goes solid and blocks the pipe, you say you filled the tank by hand was it full before you tried to fill the rad and how much water did it take to top it up after you filled the rad in bucket fulls?

    There is very little pressure of water to fill the rad if the tank is in the same room, so even a restriction in the pipework will cause problems.

    Usually bleeding is done with the pump off but on some systems you may get a better result with the pump on, perhaps with the working rads turned off.
     
  8. footprints

    footprints

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    That's a couple of Gals in old money about right for a rad.

    You could try draining off a gal or so from the rad and get someone to watch the water level to see if it drops then refill and get them to watch to see if it goes down as you try to bleed. At least you will confirm if water is entering the system as it should.

    If it's ok you could try overfilling the tank to see if a little more head helps then bail out if it works. But get someone filling as you go you don't want to kep empting the tank as you try.
     
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