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General: Push-to-flow radiator valve

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    When a thermostatic radiator valve gets hot enough, normally the thermostatic head pushes the pin inwards, to shut the valve.

    We have one that works the other way - the pin must be pushed in to allow flow, and it springs out to shut flow off. It's on a towel radiator. No markings on it.

    I want to replace just the thermostatic head, but obviously most of the new ones work the normal way round. I need one that pushes the pin to allow flow.

    What name or term should I be searching for, to find this kind of thermostatic head?

    Thanks!
    • CommentAuthorLF
    • CommentTimeMar 1st 2023
     
    Intrigued as to why you are asking ? ;-)

    Normal valve will be an expansion caused by temperature that is closing the valve - a fail open valve.
    I think it will be a thermal bypass valve you are after - a fail closed valve/expand to open.

    If you cannot find such a thing then if you made a bypass line around the radiator then a standard valve on the bypass valve would achieve your desired function ? Bypass line would link flow and return.

    I am pretty sure Danfoss do something like what you want.
    https://www.danfoss.com/en-gb/products/dcs/valves/thermostatic-valves/#tab-overview
  3.  
    As LF, TMV's close by pressing the pin in. That's why rads don't heat up after being shut off during the summer, as the pin stays stuck in.

    Of all the "wonderful" things I do for clients, the greatest "magic" is to make "broken" rads work by pulling and oiling the pin, in two minutes :bigsmile:
  4.  
    Yes, I've done that 'magic' too! Usually on the old valves that had a specific flow direction. This is the first TRV I have ever come across that opens when the pin is pushed in. I guess it is an oddity that may have originally come supplied with the towel rail.

    Hi LF, I need to replace the thermostatic head as the original was damaged by the previous owner, who replaced it with a standard head which obviously can't control the temperature as it acts in the wrong direction. I don't want to drain the system to modify pipes (airlock guaranteed!), but if I did I would replace the whole TRV.

    I tried the terms you suggested (thanks!) but no luck. Danfoss do lots of normal TRVs, but their push-to-flow valves seem to be for industrial uses.

    Suggestions very welcome!
    • CommentAuthorowlman
    • CommentTimeMar 3rd 2023
     
    Could it be that it was never intended to be thermostatically operated, i.e. that the valve itself is a spring loaded manual one.
    The valve internal spring keeps the valve pin closed,( pushed out), which is only opened when a manual valve head is screwed down pushing the pin in. The previous occupant has, inadvertently, fitted a standard wax capsule TRV valve head.
    • CommentAuthorLF
    • CommentTimeMar 4th 2023
     
    Without venting down a cable tie or something to compress and force it open?
    A radiator valve cap with epoxy packer?
  7.  
    Thanks all!


    @LF, I can make it flow by setting the retrofit 'normal' thermostat head to "0 Frost" temperature, which pushes the pin right in and gives maximum heat. However it cannot control the temperature as it reacts in the wrong direction, so have to use the lockshield to adjust temperature :neutral: so I will definitely need a new thermostatic head.

    @Owlman, that's an interesting idea, I'll do some searching.
    • CommentAuthorLF
    • CommentTimeMar 6th 2023
     
    Have they used it as a minimum flow / always taking pump flow system?
  9.  
    Not with this rad, that's done by a bigger radiator elsewhere.

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