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TrVs not working?

Discussion in 'Plumbing and Central Heating' started by Dedekind, 8 Nov 2019.

  1. Dedekind

    Dedekind

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    Hi

    We moved to this house about 6 months ago, in need of renovation. At the beginning all the radiators worked fine but with the caveat that they were always super hot, the TrVs don't seem to do anything to them.

    Since then we did all upstairs including new plumbing and radiators -- we left downstairs as is, as well as the old boiler, to be completed next year.

    The new radiators work better than the old ones: the ones with TrVs seem to be ok although not perfect, one of them for example only lights up at 4 and it's pretty much the only heat setting. Others are a bit less bad. The one in the bathroom has manual valve and it's same as downstairs: turning it on a little bit is the same as turning it on all way.

    I bled every one as much as I could. Some still have a bit of cold patches in the bottom which is probably not air.

    System is gravity.

    Is there something I can do? When we change the boiler a full system drain will be performed so I imagine everything will be fixed then, but still I'm curious..
     
  2. Crezzer

    Crezzer

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    Are they cheap unbranded TRV's?
     
  3. Dedekind

    Dedekind

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    No, most of the old ones are Honeywell. The new ones are Drayton
     
  4. Crezzer

    Crezzer

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    Trvs dont control the heat of the radiator they control the heat of the room, so if the room is warm the trv might not open untill no 4 or 5, like wise if the room is cold they might open at 2 or 3.
    Trvs are a bit cumbersome for accurate temperature control so you will get some variance.
    If a manual valve is open a little bit or full it wont make any difference to the temp either, they are only used for balancing. Most bathroom rads/towel rails are on manual valves as if all the trvs shut done the pump still has an open circuit to pump round.
     
  5. D_Hailsham

    D_Hailsham

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    Remove each TRV head and check that the exposed pin in the valve body will go down when pressed and pop up when released. If the pin is stuck 'up' you may be able to free it with some silicon oil. WD40 is not recommended as it will rot the seals. If the pin is stuck down (rad always cold) tapping the side of the valve body may release it. Pulling the pin up with pliers is not advisable as the pin may come out, together with unwanted dirty water.

    Cold patches at the bottom will not be air, which rises to the top of the rad and is expelled when you bleed the rad; it's more likely to be sludge. Removing the rad and hosing it through under mains pressure may help. Putting Sentinel X400 in the system and leaving it there for a few weeks should help as well. You will have to drain the system at the end, refill and add the appropriate quantity of inhibitor (X100)

    As you have changed some rads, the system will need rebalancing.
     
  6. Dedekind

    Dedekind

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    Interesting about the manual valve, makes sense. I know TRVs don't actually control the temperature of the radiator, but they help to the feeling of that. If the room is warm then the rad will heat up occasionally so it won't be as hot to touch I suppose, compared with being on for a long period.

    Thanks a lot. I will check the pins today. For the sludge, could it be affecting the new radiators as well? Given plumbing has been replaced only upstairs, I think this can be possible.

    Hopefully all will be sorted in a few months when chanign the boiler and the rest of the radiators.
     
  7. Gasguru

    Gasguru

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    Forget sludge for the moment...it very rarely causes radiator problems. Start by balancing the system first...that will cure 99% of heat problems.
    If however you have a 10 to 20 degree temperature drop across the radiator pipes and still have cold patches then you have genuine sludge.
     
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  8. D_Hailsham

    D_Hailsham

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    TRVs control the room temperature by controlling the heat emitted from the radiator. They do this by altering the flow through the radiator: faster flow means a higher return temperature. consequently a greater output, slower flow results in a lower return temperature, so a lower output

    A TRV is fully open if the room temperature is more than two degrees below the set temperature. So setting a TRV to Max does not mean the room willl heat up any faster. All it does is keep the rad at maximum output while attempting to bring the room up to 28C-30C, depending on the TRV
     
    Last edited: 5 Dec 2019 at 11:32 AM
  9. ericmark

    ericmark

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    With the gas modulating boiler I found the TRV would stop radiator getting that hot, [​IMG] these you can hear adjusting and they seemed to keep the radiators at just hot enough to hold room so target and current were the same. But with the oil boiler since boiler switches on/off rather than modulating, found radiator actually gets quite hot at times. The cheaper heads [​IMG] I found work nearly as good as the expensive ones, but only show target temperature, don't show current, but thermometers in same room show they work well. The cheaper ones actually tell you if not working with fault codes F1, F2, F3 and battery symbol. Looking at between £8 and £60 for electronic heads, I got 5 of the blue tooth versions of the eQ-3 lower picture for £15 each.
     
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