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Most Radiators Warm - But Three Are Stone Cold

Discussion in 'Plumbing and Central Heating' started by seafuryfan, 4 Nov 2005.

  1. seafuryfan

    seafuryfan

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    Hello, we've been in this old house for a year now. The pumped CH system supplies HW:
    first to upstairs rads + HW cylinder, then I suspect (in this order), to downstairs via a ground floor through passage rad, then to 3 rads in an ground floor only extension bldg, then (I suspect) all the way back to the boiler via two ground floor living room rads, and a halway rad.

    When the temperature is not too cold, the last three rads heat up fine, but tonight at around +5 outside, they are stone cold. This often happens, and sometimes not just to those three rads - others on the ground floor sometimes do just not seem to come on or are barely warm. The duff rads show no signs of heat when the CH activates or afterwards. Yet on other, milder nights this year they have been piping.

    The upstairs rads are always piping hot, so we had Myson 17 TRVs fitted to all rads in the house last year (to try and regulate heat to boost the downstairs ones - I'm waiting for someone to say that was a wrong move). I can't say if this rad problem was occuring before we had them fitted.

    Other stuff: Tonight I turned the upstairs TRVs fully open, in case this would help things. The rad heat increased upstairs, but there was no change downstairs. We have one new CH on/off room stat in the 'cold' living room which is yet to be calibrated but which is fully open and the power light is on ok. I have bled all radiators and there is water coming out of all of them.

    I have read that (and I quote from the good old RD red book) 'when TRVs are fitted to all radiators in a system, a valved by-pass should be provided in the system to maintain a minimum water flow through the pump'. I don't know if the plumbers fitted one of these. The book also says, 'TRVs do not swith off motorised valves to prevent boiler short-cycling' (visions of a boiler atop a uni-cycle). Relevant? Irrelevant?

    Any advice much appreciated, I appreciate that any replies may take a while

    Rick
     
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  3. corgiman

    corgiman

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    try turning off those rads that are working and turn on the central heating and see if you have an airlock, if so the cold rads should start heating up. If no you may have a more complicated problem (sludge stuck trv's etc) and I would advise that you contact a reputable engineer to check it out.
     
  4. seafuryfan

    seafuryfan

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    Thank you corgiman. I did as suggested and the rads are not stone cold any more but are barely luke warm. I didn't do this action from cold, but while the heating was hot. I turned the heating off, turned off all the rads, and turned it back on again. And I ended up an hour later with those barely warm rads.

    Should I have let the system go cold first? I'm sorry I'm so dim but this is why I could never be a handyman. Nothings ever seems to be one or the other, always this fanyying around :confused:

    Thanks,

    Rick

    PS: The TRV has a liquid sensor according to the company's blurb. does this mean it still has a needle which can stick?
     
  5. corgiman

    corgiman

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    think you may have some circulation problems there, get a decent plumber/engineer to check the thermostatic rad valves and maybe check the water for sludge etc... fernox do a rather nice testing kit so make they have one of those and use it before saying you have a sludge problem

    yes they do the liquid just expands and pushes it down or contracts and a spring pops it back up
     
  6. seafuryfan

    seafuryfan

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    Thanks for the advice corgiman, I've turned the system on from cold this morning with the same result. Next stop: the plumber. I'll post the outcome.

    If I can be of assistance in the future because I happen to live in the UK, please let me know ;)
     
  7. seafuryfan

    seafuryfan

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    Follow up on this problem:
    The plumber visited today and suspected a faulty valve which controlled CH/hot water on/off. Thing is, he couldn't find it. The original CH installers decided it would be a good idea to put this electric valve (which will obviously breakdown someday) under the first floor at the top of the stairs - which enventually we found after ripping up floorboards. Very convenient - not. This valve was plumbed into a three way union which served CH and hot water. no wonder I was getting the rads on with hot water only selected!
    He's going to install separate hot water and CH valves with an additional new pipe running from the boiler to the hot water tank. This will mean that we will have CH OR hot water - what it should have been in the first place. you should see the electric jungle we've also uncovered!!
    When you buy an old place, you really have little idea of what you're going to be buying, thats for sure. It's a good job this place has a good view and plenty of room for the kids to grow up in, inside and out.
    Thanks again to the replies to this post - its a great site.
     
  8. DIYnot Local

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