One radiator won't heat up at all

Discussion in 'Plumbers' Talk' started by DIYenthusiast, Jan 10, 2020.

  1. DIYenthusiast

    DIYenthusiast New Member

    This radiator was working fine for two years. It stopped working about a year ago. The rad had been moved from one part of the room to another three or four years as go.This was done by professional plumbers by extending piping from the next room. The rad looks like it id the last on the circuit, and physically the closest to the boiler.

    CHECKLIST OF THINGS DONE SEPARATELY ON DIFFERENT OCASSIONS BUT NO LUCK IN GETTING IT TO HEAT UP

    • Bled radiator a few times. One time the inflow pipe and part of the rad warmed up just barely (not warm but you can feel there was a bit of barely warm water in there). We had central heating on an hour earlier.
    • TRV pin is fine moves down then up freely if pushed down
    • TRV open
    • Lockshield open
    • Closed all upstairs rads but kept downstairs open hoping to increase flow to the downstairs rad including the non-working
    • Closed all but one other radiator hoping to concentrate flow into the non-working rad
    • Drained the system once or twice over the last few months again no luck
    • One time the TRV pin leaked after playing around with the pin. Considerable amount of water flowed out into a bowl placed just under under the TRV. This water along with the inflow pipe and the TRV was boiling hot. I though I had finally fond it but the rad did not heat up at all and the return pipe along with lockshield valve stone cold as always.
    Why didn't this very hot water get into the rad? Could the valve be faulty, or is there a block on the return pipe leading up to this radiator. I can pinpoint exactly where the pipes normally go cold when the heating is on. Its at the point where this room's pipework meets the pipework to the room next door, where it is connected from.
     
  2. Hans_25

    Hans_25 Well-Known Member

    Could be an air lock, or blockage.
     
  3. techie

    techie Member

    does water drain out of the lockshield valve if you disconnect it from the rad and open it?
     
  4. DIYenthusiast

    DIYenthusiast New Member

    Not got as far as disconnecting the valves from the rad. Could do this but might want to wait till the winter is out the way. All other rads are working great so don't want to risk messing anything up while it is still cold. But I would welcome advice now so I can prepare to do what is necessary. I want to call in a plumber as last resort.

    If water doesn't drain out of the lockshield, then what might be the problem. The rad does however drain out fine of its drain valve at the bottom.

    Interestingly, one time I drained it with TRV valve open and lockshield closed and water came out fine, then I closed the TRV and opened the lockshield side but water did not drain out. That said, if I recall correctly, I think water did drain out another time with lockshield open and TRV closed (but I cannot be 100% sure I remember this correctly).
     
  5. Hans_25

    Hans_25 Well-Known Member

    If you've turned off all rads except the cold one and it still doesn't heat up, must be a blockage or faulty valve I reckon.

    Could try bleeding this radiator with one valve turned off, then the other valve turned off. If one valve is stuck closed then with the other valve closed, you'll get naff all water coming out the bleed valve.
     
  6. DIYenthusiast

    DIYenthusiast New Member

    You mean the TRV could be faulty? Where would the blockage be you reckon from what I've described if the TRV is fine.
     
  7. DIYenthusiast

    DIYenthusiast New Member

    Will try this later and report back.
     
  8. Hans_25

    Hans_25 Well-Known Member

    TRV valve or lockshield on other end could be faulty, perhaps washer thingy has come loose and is blocking things, or is stuck shut. Blockage is most likely at the entry/exit of the radiator caused by sludge build up, but could be anywhere. Could be a solder fitting where there's a glob of solder compounded by sludge.
     
  9. DIYenthusiast

    DIYenthusiast New Member

    I bled the radiator with each end closed. Water did come out both times. Since I had the central heating on half and hour prior, the inflow pipe (the 2 metres leading up to the radiator that normally stays cold) and the TRV valve got pretty hot as I was bleeding for a while. The rad itself remained cold apart from an inch to the extreme right bottom immediate to the TRV. The return pipe and lockshield remained cold. But since the rad is not getting hot, the return pipe would remain cold wouldn't it?

    Does this mean the blockage is in the rad itself at the entry on the TRV side. How can I dislodge it? Anyway outside of taking it out to the garden and putting high speed water through it with a hose.
     
  10. Hans_25

    Hans_25 Well-Known Member

    Could try some Sentinel X.400 but really need a Magnaclean in your system for best effect. Either way you'll need to drain down and flush out at some point.
     
  11. DIYenthusiast

    DIYenthusiast New Member

    I closed both valves again today, opened the lockshield end and barely any water drained via the drain off at the bottom of the rad, but drained normally with the TRV open. The water was quite black to begin with but became more clearer.

    Not draining with only lockshield open. What does this mean? Possibility the lockshield valve is faulty. But it does open and close as far as turning the spindle is concerned.

    Regarding adding Sentinel, I could do this via the filter we have fitted, a Fernox TF1. My only worry is that it is located just above the boiler (as opposed to under it with most people). This means it would enter the boiler quickly after it is added, rather than going around the system first. Is this anything to worry about? The boiler is working flawlessly at the moment so don't want to jeopardise anything.
     
  12. terrymac

    terrymac Well-Known Member

    Adding sentinel will not do anything if it can't flow freely ,it certainly will not unblock a pipe.
    Is the radiator a vertical ,designer type?
    Is the system pressurised or fed from a f&e tank in loft ?
    If you close both valves on the rad ,then
    open the air bleed ,after a short while water will stop coming out. If you then open the lockshield ,does water then start to flow strongly from the still open air bleed ?
     
  13. DIYenthusiast

    DIYenthusiast New Member

    This is the last rad in the circuit, a traditional single panel convector type (it is horizontal) , and was actually moved from another part of the room a few years back. Worked well the first two to three years. The rest of the radiators are heating up really well.

    It's a pressurised system.

    I do wonder if the rad next door is stealing the heat. That rad gets extremely hot very quickly. But I did the balancing and turning most of the other rads off. Nothing seems to work.
     
    Last edited: Jan 13, 2020
  14. terrymac

    terrymac Well-Known Member

    And the answer to my last question is ????
     
  15. DIYenthusiast

    DIYenthusiast New Member

    Will get back to you with that either later or tomorrow. Won't get a chance to bleed it for a while.

    By TV the way, I watched this video on YT a few days ago with this guy taking the bleed valve out and connecting a hosepipe to it and then bleeding it by opening either end, one at a time. The idea is that if its an airlock the larger opening will likely force it out.
     
  16. terrymac

    terrymac Well-Known Member

    As your system is pressurised it's highly unlikely that you have an airlock.
    What diameter pipes run to the radiator by the way ?
     
  17. DIYenthusiast

    DIYenthusiast New Member

    The diameter I am sure is 15mm. Not measured it but it looks like the standard size.

    Sorry, I think I do have have the f&e system. Wasn't completely sure the difference between the two. Still learning.

    What I can tell you is this. I have a pressure gauge on tbhe boiler and when pressure is low, I use the filling loop to repressurise the system. But this could be something quite irrelevant to what you are asking.
     
    Last edited: Jan 13, 2020
    terrymac likes this.
  18. Hans_25

    Hans_25 Well-Known Member

    In which case you won't have an F&E tank in the loft - the heating pipes are "sealed", topped up from the mains to around 1.5 bar or so.

    Now what you can do, carefully, is to use the filling loop to flush out the system. Just be careful as if you do have a blockage you'll have mains pressured water backing up behind it.

    So, find a drain cock on the ground floor and fit a hose to it and out to the garden. Open drain cock, turn on filling loop, this will get water flowing through the system. Then, CAREFULLY, turn the rads off one by one to just leave one rad open - water will flush through that single rad. Then turn a 2nd rad on and the first rad off, continue through all the radiators. When you come to the blocked radiator, have another rad open so water is flushing through two rads and see if the blockage clears.
     
  19. DIYenthusiast

    DIYenthusiast New Member

    Thanks. This looks a more convenient method. I am going to use the drain cock of the rad that isn't working.

    First, I have a couple of questions.

    I normally need to open two screw type nuts (or whatever they are) with a screwdriver to start the flow. How much do I turn them? I normally turn them ever so slightly to ensure it fills up gently as I need to keep an eye on the pressure gauge. Do I need to open them up more than usual to increase the flow pressure?

    You say to close all rads except one. This means closing both the TRV and the lockshield sides, right? Also, how long do I keep each one open before closing it and opening the next one? And you say, when it comes to the blocked radiator to leave one other one open. But do I close that one to finally leave only the blocked one open at the very end?

    More importantly, the pressure of the water won't risk a leak will it?
     
    Last edited: Jan 14, 2020
  20. Hans_25

    Hans_25 Well-Known Member

    Hi DIY
    - the two valves to top up the water are in series, so open one fully, then gradually open the other. Just keep an eye on the pressure valve as it should remain at zero (with the drain cock open), if pressure starts to rise then you know you've got a blockage. You should have both valves wide open to get maximum flow of water and flush things through.
    - To close a rad you only need one valve closed, so either the TRV or lockshield, which ever is easier and is not set to balance the rads. I have Drayton TRVs which have a setting to regulate flow, so I close the lock shields which are otherwise fully open. Most TRVs however need the lock shield set to regulate flow so might be easier to close the TRVs.
    - Keep each rad open until water is clear, might take a wee while. And when you come to the blocked rad, once you've determined its not totally blocked you can open up the flow to full to give it a good flushing.
    - The water pressure should be fine unless you have a blockage - just keep an eye on the boiler pressure meter which should stay at zero.
     

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