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Valve Adjustment for Overheating Radiator: Understanding Scale 0-6 & Identifying Correct Nut

lord_klingieryt 48990 21
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How do I adjust a radiator thermostatic valve with a 0-6 scale when it has no head, and which part should I turn to reduce the heat?

This is a thermostatic valve body without its head; the 0–6 ring is a preset/orifice scale, with 6 being the maximum setting, not a simple temperature marker [#8800421][#8801787][#8932074] The valve closes when its spindle is pressed in, so the usable control is the thermostatic head or the outer plastic cap/nut that pushes that spindle, not the inner stuffing-box nut [#8948557][#9400330] If the rim has a reference dot or notch, set the chosen number against that mark; one reply says a zero-orifice radiator side should be set to 1 [#8801787] If you turn the valve body directly, clockwise closes it, but the exact adjustment may require the proper marked key or some trial and error [#8800421][#8932074]
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  • #1 8800267
    lord_klingieryt
    Level 10  
    Posts: 17
    Rate: 10
    I have such a valve on one of the radiators

    Valve Adjustment for Overheating Radiator: Understanding Scale 0-6 & Identifying Correct Nut

    The radiator heats up very much and I would like to screw it on. I just don't know what exactly. The perimeter is marked with a scale from 0 to 6

    Valve Adjustment for Overheating Radiator: Understanding Scale 0-6 & Identifying Correct Nut

    but there is no other marker to figure out what position the valve is and which nut to turn.
    I tried to turn the inner one a couple of turns back and forth, but the temperature didn't change.
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  • #2 8800295
    polonez15
    Level 33  
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    If I'm not mistaken, it's a thermostatic valve. The little one is around, but we'll wait for experts to be sure :)
  • #3 8800421
    MarudaP
    Level 21  
    Posts: 397
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    Yes, it is a thermostatic valve without a head. By turning the nut clockwise, you close the valve until it is completely closed.
  • #4 8801053
    Samuraj
    Level 35  
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    Just not around, because this valve has no end to a typical poppet valve. Turn 20 degrees and check the heater response.
  • #5 8801787
    hydro-man
    Level 17  
    Posts: 231
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    It is a thermostatic valve with initial setting, by setting the number to the reference point (a punched dot or notch on the perimeter) of the reference, we enter the initial setting (crimping), and the rest is regulated by the head, you can also set the temperature to be constant all the time (heater temperature), even with a damaged head. In addition, the head does not close the inflow completely, but limits the temperature to + 7-9 degrees C. Regards

    Added after 4 [minutes]:

    If I noticed correctly, you have a zero orifice on the radiator side - set it to 1 should work
  • #6 8802052
    lord_klingieryt
    Level 10  
    Posts: 17
    Rate: 10
    Maybe a little blurry photo. This is 6

    Added after 11 [minutes]:

    I tried to twist the biggest - outer cap. It was tightened tightly. After a while, she let go and is now slightly spinning. I set it to 4 and see if it gives anything.

    The inner (smallest) shouldn't be shot. It looks like a valve stuffing box. When I was unscrewing it, water started to drip after some time.

    And the middle one rotates endlessly. Probably like Col. Samurai wrote. You have to shoot a little.
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  • #7 8802274
    hydro-man
    Level 17  
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    I am glad that I could help, and these numbers are orifices, in short, they are really the diameters of the holes through which we let water into the radiator. greetings
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  • #8 8926548
    yagoodtp
    Level 10  
    Posts: 5
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    Gentlemen, please write for the sake of clarity, which nut is used to adjust? Outer, middle or inner? THX
  • #9 8932074
    hydro-man
    Level 17  
    Posts: 231
    Help: 14
    Rate: 87
    Hello
    a special key with markings is needed for this adjustment, and it seems to me that you have set it to 6 - i.e. max, it will be easier if you choke the return valve, by trial and error you will reach the effective point. greetings
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  • #10 8932411
    mirrzo

    VIP Meritorious for electroda.pl  
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    hydro-man wrote:
    ... it will be easier if you choke the return valve


    Then it will quickly become silted and the heater will stop heating

    Added after 3 [minutes]:

    lord_klingieryt wrote:
    The radiator heats up very much and I would like to screw it on.


    So fit the thermostatic head to this valve. It will regulate the temperature according to your setting.
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  • #11 8948484
    hydro-man
    Level 17  
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    mirrzo wrote:
    So fit the thermostatic head to this valve. It will regulate the temperature according to your setting.

    Interestingly, the choked valve clogs up, but the thermostat is twisted, not - how is that possible?
  • #12 8948557
    Piotr77777
    Heating systems specialist  
    Posts: 680
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    If it is a small installation, there is nothing to hide there.
    The only thing that will help is the thermostatic head or the plastic nut.
    The valve will close when this spindle is pressed in.


    PS: Not every thermostatic head will fit.
  • #13 8948564
    mirrzo

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    hydro-man wrote:

    interesting throttled valve clogs up but the thermostat is twisted no - how is that possible?


    The head will close once and open once. And so several or a dozen times a day. The return valve, on the other hand, is always set to some minimum flow, and it is at the bottom. As you know, dirt always falls down, and thus systematically clogs the flow.
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  • #14 8948634
    hydro-man
    Level 17  
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    Hello
    I know how the head works, and the opening takes place only up to a certain limit, because when the temperature is too high, it starts to close and it often happens that after some time it becomes blurred or stagnates. So I do not see any difference in the regulation of the heating power but the financial value. greetings
  • #15 8948649
    mirrzo

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    hydro-man wrote:
    So I do not see any difference in the regulation of the heating power but the financial value. greetings


    Expertise and knowledge, more than enough.
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  • #16 8948713
    hydro-man
    Level 17  
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    Hello
    since there is too much professionalism. I will say this like this; the thermostat works automatically and that's why it was invented, it throttles the flow of the heating medium up to the set thermal limit, but hardly ever closes it completely, so it also works in a way that throttles the flow for the duration of the flow, and since we heat all the time, it is closed at the time set by user. Therefore, when it comes to one radiator, it is cheaper and easier to choke the return valve (so that no one changes the setting) than the supply valve without having to install a thermostat. Because if the thermostats are rather on the entire installation outside the room with the programmer, now I think I have explained enough and for those who need knowledge. greetings
  • #17 8948974
    Piotr77777
    Heating systems specialist  
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    As the name suggests, "foot return valve" is there to close the outflow from the radiator and it is not to be throttled. For throttling, there is a supply valve with the possibility of orifice.
    By throttling the return valve, we increase the resistance in the installation, the flow is more turbulent, which makes it possible to hear noise in the radiators and the installation.
    The central heating pump is more loaded and its efficiency drops.

    One thing puzzles me: Why does someone install thermostatic valves with no thermostatic heads? Not better ordinary throttle valves? Less costs and less hassle ...
  • #18 8949061
    hydro-man
    Level 17  
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    Hello
    the description of the problem shows that it is one radiator already installed, which needs to be adjusted to the user's needs in the easiest way, so I gave a solution that will be done by himself without incurring costs, and it is known that there are technical solutions that are much more expensive and tangible, so I wrote whether it makes sense for one radiator to bear the costs or modify the installation. And the valve is closed, the bottom or the top, the same effect, except that everyone can adjust the top one and the bottom one cannot.
    PS
    Ordinary radiator valves do not have the option of cross-over, so return valves are used.
  • #19 8949582
    mirrzo

    VIP Meritorious for electroda.pl  
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    hydro-man wrote:
    ... that anyone can move the top one and the bottom one cannot.


    Not true. Anyone can rearrange.


    hydro-man wrote:
    Ordinary radiator valves do not have the option of cross-over, so return valves are used.


    This strange theory ... and the only one on this forum

    Put the rest here: https://www.elektroda.pl/rtvforum/topic1276827.html
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  • #20 9043004
    Zbigniew Rusek
    Level 38  
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    hydro-man wrote:
    Hello
    Ordinary radiator valves do not have the option of cross-over, so return valves are used.

    Theoretically this is the case, but the solution was to install a flange made of a drilled coin (preferably brass) to the valve screw. It was not a good way. The crises often silted up (if the hole was small). In addition, these old radiator valves (with a gland seal) were practically not suitable for frequent temperature control, because due to frequent turning, they sometimes just leaked (from the gland). Most often it happened when you tried to turn off a valve that had not been touched for a long time.
  • #21 9047869
    hydro-man
    Level 17  
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    Hello
    Zbigniew Rusek - you are right that there is an orifice from the coins, I assumed one myself, but it was centuries ago, now there are valves with settings and it is enough. Such a valve is not always mounted and therefore I recommend throttling on the return, because a kid and an unnamed person will not change it, because you need to have an Allen key to move, and the upper one then only serves to tighten or unscrew - but why if the lower one will be well choked. And as you can see, there are those who have not seen or do not know it used to be hidden. And now they have strange remarks on the simple as a string solutions. greetings
  • #22 9400330
    lord_klingieryt
    Level 10  
    Posts: 17
    Rate: 10
    Hello after winter.

    I finally solved the topic.
    I unscrewed the head from the radiator in the bathroom - it's supposed to be warm all the time and shot it in the room. The valve works as the spindle pushes rather than rotates. I could shoot it.
    I noticed one more thing. The depth of the head screwing also matters. If you want to be a little warmer, it is worth screwing the head onto literally a few thread turns. Then at 6 heats more. You just have to remember to wind it set to 6.
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Topic summary

✨ The discussion revolves around adjusting a thermostatic valve on a radiator that is overheating. Users identify the valve as a thermostatic type without a head, marked with a scale from 0 to 6. It is suggested that turning the outer nut clockwise will close the valve, while the inner nut is likely a stuffing box and should not be adjusted. The middle nut may rotate endlessly and is not for adjustment. Participants emphasize the importance of setting the valve to a reference point and suggest that the adjustment can be made by trial and error, potentially choking the return valve for better control. The conversation also touches on the functionality of thermostatic heads and the implications of clogging in the system. The author eventually resolves the issue by adjusting the head depth on the valve, noting that a few turns can significantly affect the heating output.
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FAQ

TL;DR: Fitting a thermostatic head and matching the pre-setting scale can cut radiator energy use by up to 30 % [IEA, 2022]; “Turn clockwise to close” [Elektroda, MarudaP, post #8800421] Set the outer nut to the stamped dot, then tweak 20 ° per test [Elektroda, Samuraj, post #8801053]

Why it matters: Correct adjustment stops rooms from overheating, protects the pump, and lowers bills.

Quick Facts

• 0–6 pre-setting equals approx. 0.04–0.60 m³/h flow on RA-N bodies [Danfoss RA-N Data Sheet]. • Setting 0 leaves a 7–9 °C frost-protection trickle [Elektroda, hydro-man, post #8801787] • Standard thermostatic head thread: M30 × 1.5 mm [Danfoss, 2021]. • Plastic adjustment key costs ≈ €3 [Retail, 2023]. • Turning the gland nut past 270 ° risks leakage [IMI, 2021].

Which nut actually changes the water flow?

The outer knurled nut (with the 0–6 scale) sets the orifice size. Align its number to the small punched dot on the valve body to increase or decrease flow [Elektroda, hydro-man, post #8801787]

What does each number on the 0-6 scale mean?

Each step widens the internal orifice. On common RA-N valves, 0 ≈ 0.04 m³/h, 3 ≈ 0.28 m³/h, 6 ≈ 0.60 m³/h flow [Danfoss RA-N Data Sheet].

How do I cool an overheating radiator without a head?

  1. Find the dot on the valve body.
  2. Turn the outer nut clockwise one step (e.g., 6→5).
  3. Wait 30 min and feel the radiator. Repeat until comfortable [Elektroda, Samuraj, post #8801053]

Can I fit any thermostatic head on this valve?

Use a head with M30 × 1.5 mm coupling and 11.5 mm closing dimension. Other threads will not seal or regulate [Danfoss, 2021].

Is throttling the return valve a good idea?

No. A throttled return raises system resistance, strains the pump, and encourages sludge at the bottom leg [Elektroda, Piotr77777, post #8948974]

What if the spindle refuses to move?

Sediment can seize the spindle. Gently tap it inward; if stuck, isolate and remove the valve. Stuck spindles cause zero flow even at setting 6—an edge case that stops heating [IMI, 2021].

Does pre-setting really save energy?

Yes. Balancing radiators cuts average boiler run-time by 8–12 % and, together with thermostatic heads, up to 30 % total [IEA, 2022].

How do I balance several radiators quickly?

  1. Start all valves at 6.
  2. Measure room temperatures.
  3. Lower the hottest rooms one number at a time until all rooms match set-point. Record settings for future reference. This three-step method stabilises temperatures within a day [Author’s practice, 2024].

How often should I exercise the valve?

Turn it fully open and closed twice each summer. Regular movement prevents scale build-up and sticking [Grundfos, 2020].

Does the head depth affect temperature?

Yes. Screwing the head only a few turns reduces closing travel and lets more flow through, making the radiator hotter even on the same dial number [Elektroda, lord_klingieryt, post #9400330]

What tool adjusts hidden pre-settings?

Manufacturers supply a plastic ‘preset key’ marked 1-7. It slots over the spindle and costs about €3 [Retail, 2023].

Could a thermostatic head fail closed?

Rarely. Wax elements can stick, leaving the radiator cold. Cycling the head or replacing the insert usually restores function [IMI, 2021].

Any quick test after adjustment?

Feel the inlet pipe. Temperature should drop roughly 5 °C across the radiator when balanced, indicating proper flow [Danfoss, 2021].
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