Radiators not working

Discussion in 'Plumbers' Talk' started by Duncan T Wilson, Jan 28, 2019.

  1. Duncan T Wilson

    Duncan T Wilson New Member

    Hi folks,

    I am looking for some advice on my Central heating. I have recently moved into a 1930s semi with an open vented system and 11 rads. Some of the downstairs rads were heating only partially or not at all, so I drained the system and put some cleaner into the central heating feed tank, refilled and then drained again after a week. When draining, the water was running clear. But now the problem is even worse - almost no heat getting to any of the downstairs rads (upstairs are still all fine).

    From reading around I think the problem may be with the pump, a grundfos scelectric 15-50 (not sure how old but it has a manual dial for changing the speed). After the second draining it now has a knocking sound when on speed settings 2 or 3, but not on 1. I understand this might be air in the system, but I've bled all the rads and the pump and no air is coming out. It has been 4 days since I last drained the system. Also the pump is very hot to touch - I have read this means it is probably on its way out?

    Only other thing is that there is some blue residue around the joint connecting the heating feed tank to the system, just above the pump. I take this means there has been, and maybe still is, a leak?

    Any advice on how to isolate where the problem lies? Should I be replacing the pump or is there anything else to try first?

    Many thanks in anticipation.
     
  2. KIAB

    KIAB Super Member

    Want to give the cleaner some time to work, cleaner like Sentinel X400 can be left in system up to four weeks,ideally you need a magnetic filter (Magnaclean Pro 2, the easiest to fit & among the best) on CH return to collect any crud, rather than recirculating around system again after being dislodge by the cleaner.

    Also probably dragged a lot of crud from header tank down into system when draining down,I alway clean F&E tanks with wet n dry vac first before fully draining down, can save you a lot of grief later.
     
  3. spirits are real 2016

    spirits are real 2016 Screwfix Select

    it could still be a air lock what you could try is turning off the working rads and then see if the others heat up making sure both isolaters are turn on and is the motorized valve working.
     
  4. Dam0n

    Dam0n Screwfix Select

    It sounds more like a combo of a balancing problem along with air in the system and possibly a pump on way out. The fact it's getting hot could just be because of the hot water in the pump body itself however.

    Try tuning off all of your radiators on the 1st floor and see if any heat gets moved to the downstairs rads. If this works we can go from there to get the system balanced and bled. Also put your pump on its highest setting.

    Do you have any other vents on the system? Possible they are the old style bleed valves rather than the AAV's you see cutting about today.
     
  5. Duncan T Wilson

    Duncan T Wilson New Member

    Hi folks,

    Thank you for taking the time to reply to my post with these helpful comments.

    As you suggested, I turned off all the upstairs rads and this led to some good heat getting downstairs. I think part of the problem was the bathroom radiator. It has been fitted with two capped lockshields so I always left it as it was, although it was very hot. I looked into balancing the system as you suggested and followed the instructions, turning one valve to just a quarter open. This has helped a lot - I can now get the radiators in the bathroom, babies room and living room all hot. But if I turn on another, e.g. in the kitchen, there is a fair drop in heat in the living room.

    I think you are right about crud from the tank upstairs getting into the system after I drained it, I went up to have a look and it was quite a mess. I am trying to clean it out but it's a bit of an awkward job without a wet and dry vac - bought a hose the other day so I'm going to try and siphon it off.

    I was considering trying to replace the pump myself, but I am currently struggling to replace an old radiator valve with one with a drain cock so I think I have already got to the limit of my plumbing abilities and will have to get a professional! After that I will try to balance the system properly. In the meantime I will start a new thread about getting this radiator valve fixed!
     
    Muzungu likes this.
  6. gas monkey

    gas monkey Well-Known Member

    w d 40 all your rad therm valves make shore they work
    take the centre off the pump see if its spining
    to clear out system drain fit hose from mains water and open rad one at a time and flush it out
    do not over pressurise the system
    refill with anti scaller etc
    worked a few times for me on jobs lots of messing about but give it a go
     

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