Trv horizontal seems to close way too fast

Discussion in 'Plumbers' Talk' started by Fishleg, Nov 30, 2019.

  1. Fishleg

    Fishleg Member

    We mounted the trv on a new rad at the top horizontal, it's a Drayton liquid sensor type.

    It works fine if the radiator is cold. The radiator is always on as it's the main kitchen radiator so it's just set to 6 so I thought that means the valve should be open all the time. Problem is after about 30 mins the valve shuts, the radiator goes cold or luke warm and didn't seem to open until the pipes are cold again.

    Why is the valve closing when it's set to max? The temp in the kitchen is 19-20 with the valve set to 6 the max output.

    Have I got the wrong head do only some work horizontal?

    Thanks for any help.
  2. Severntrent

    Severntrent Screwfix Select

    If you mounted it at the top of the radiator is it possible that the rising heat turns it off super fast? if you want the valve open all the time take off the control head .
    The Teach likes this.
  3. The Teach

    The Teach Screwfix Select

    Maybe a trv is not suitable for that particular radiator installation :(
  4. MGW

    MGW Screwfix Select

    I know a TRV should work at top, but you really want to monitor return air so it turns off when room is warm, not just air around the radiator so bottom is better, also although horizontal may put the head further from radiator, with electronic types hard to read the temperature when horizontal, and although they say bi-directional I have found on the return the lock shield valve becomes critical as all valves take time to work, and the valve senses the heat of radiator too fast.

    It would seem a faulty head if turning off when set to Max, typical rated 12°C to 29°C, the eQ-3 electronic head is 5°C to 29.5°C I would guess simply too hot at the top.
  5. Fishleg

    Fishleg Member

    Can you screw these in too tight? I basically turned it to 6 and pressed the valve in and screwed it finger tight.

    I tried a different new head does the same it's no where near 29 it says its max maybe 19 room temp.

    I noticed this one is a metal pin against plastic I can't tell if the metal pin is transferring heat into the valve and turning it off early.

    Pain in the backside even their instructions say it can be placed horizontal, anyone know of a better head?

    Attached Files:

  6. Fishleg

    Fishleg Member

    That's the valve can they be adjusted other than turning it to no 6 seems way too sensitive.

    Attached Files:

  7. Fishleg

    Fishleg Member

    Bump any more ideas ? I've left it barely screwed to the rad so the trv is doing nothing now. Can't believe it's closing at 20.
  8. b4xtr

    b4xtr Active Member

    Maybe a faulty valve ? can you return it for a replacement
  9. sam spade

    sam spade Active Member

    Does the TRV pin move in when pressed (it will be hard as there's a spring) and spring back when released?
  10. Fishleg

    Fishleg Member

    Yeah pin springs in and out. Its definitely the head being too sensitive because the foot that moves against the pin is loose so freely moves up and down but after the radiator is on the foot is fully forward if I take it off the radiator and check.

    Thing is I bought 2 valves exactly the same as I've got another radiator to do so I took that one and tried it and that does the same. So either they are all pants or I'm very unlucky?
  11. sam spade

    sam spade Active Member

    Unlikely to have two TRV heads with the same fault. So something else is causing the valve to act like a switch - on or off. The cause is normally poor balancing. Has the system ever been balanced?
  12. Fishleg

    Fishleg Member

    The lock shield on the other side is fully open but what difference would it make to the trv though? I thought it just goes off ambient room temp?

    The kitchen rad is the furthest away from the boiler the rest of the rads upstairs are maybe 2 full turns open. The kitchen and front room downstairs are fully open as I wanted them two rooms to be the hottest in the house.
  13. Fishleg

    Fishleg Member

    That's the valve someone said these have to be adjusted but I got no clue what this means ...

    "take the head off, the valve has a grey knob just underneath the pin with two arrows on it, if the pipe with the valve gets hot first then the arrow should be up on the mark, if it's the other pipe that gets hot first then turn the knob so the arrow faces down on the mark, re-fit the head"

    The middle bit does screw in and out with the - - - so it looks like I can screw the middle bit in and the pin moves closer or sticks out further. What does it do though?

    Attached Files:

    Last edited: Dec 4, 2019
  14. sam spade

    sam spade Active Member

    Where did you get that from? It's not in the RT212 Instructions.

    If the LS valves are set as you say the system has not been properly balanced. A TRV doesn't just react to the change in air temperature pressing down on the pin, there's also the water flow and pressure trying to keep the valve open.

    Set all LS valves to 1/3 (that's one-third) turn open and report what effect it has.
  15. The Teach

    The Teach Screwfix Select

    The possible adjustment in #13 is for balancing purpose using the drayton balancing tool,the valve would have been supplied factory set and ready to fit.

    The sensor is picking up additional heat from the extended copper pipe below,other room heat/ventilation issues will also influence the trv operation. The response time will be extended even with the best liquid filled sensors,wax filled sensors will take an age to respond :(

    going by the part number 080815 Your trv sensor could be wax filled :confused: but who knows whats in the box.

    The trv can be converted to a manual valve by fitting a manual cap (not decorators cap) :)

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