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Head adjustment Danfoss-How to increase the small adjustment range?

niewiem1979 61473 33
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How can I make a Danfoss thermostatic radiator head regulate over a wider temperature range instead of only heating between the highest settings?

You cannot really “expand” the working range of the head itself; a thermostatic valve is supposed to close the water flow when the room reaches the set temperature and open again when it cools down [#10423246][#10422407] If it behaves almost like on/off between 4 and max, check the valve’s pre-setting under the head: it may be set too low, or the valve may be dirty/calcified and restricting flow, so remove the head, inspect/clean the valve, and if needed use the pre-setting ring in the “N” position briefly to flush it, then return it to the previous or slightly higher setting [#10423523][#10422351][#10422407] Also make sure the head is mounted horizontally and not heated by the radiator itself, curtains, or furniture, because it must sense room air temperature, not heat from the pipe or radiator [#10533034][#21790942] If the head/bellows is damaged or still does not regulate correctly, replace only the head; the valve body usually stays in place [#10547295][#10536699]
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  • #1 10422084
    niewiem1979
    Level 20  
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    Hello. I have such a danfos Head adjustment Danfoss-How to increase the small adjustment range? My problem is that it heats only between the last range, i.e. between 4 lines and max. Regulation on such a short range is almost impossible or minimal, imperceptible (hot radiators). From minimum to 4 lines, cold radiator. How to set a larger range of temperature settings, i.e.: from the minimum through all degrees of lines up to the max - so that the valve fulfills its functions and does not practically open and close as it is now. I will add that the valves are in the block on the 2nd floor, the block is on the 7th floor and I live here for half a year and I inherited such a flower.
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  • #2 10422107
    wawrzeczko_t
    Heating systems specialist  
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    Probably - the head is suitable for replacement (or a blockage at the connection of the galvanized reduction with brass causes the thermostat to malfunction. Or maybe it's these 2 kg of hemp wound on a 1/2 "thread?!)
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  • #3 10422126
    niewiem1979
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    wawrzeczko_t wrote:
    Probably - the head is suitable for replacement (or a blockage at the connection of the galvanized reduction with brass causes the thermostat to malfunction. Or maybe it's these 2 kg of hemp wound on a 1/2 "thread?!)
    The photo of the head is only a preview, it's not mine, but the same .... I don't have so much hemp. I doubt it to spoil it because I have 3 such heads and they all behave the same as I described. I suspect some internal orifice, something about it did it touch the ears?
  • #4 10422246
    mirrzo

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    So you have so much heat in the apartment that the head does not allow the medium to flow to the radiators.
    Company Account:
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    Krótka, Elbląg, 82-300
  • #5 10422283
    niewiem1979
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    mirrzo wrote:
    So you have so much heat in the apartment that the head does not allow the medium to flow to the radiators.
    Strange reasoning. The apartment is warm so I want to reduce the temperature but not close the valve! I mean something opposite to what you wrote .... the point is that if I reduce below these 4 dashes, the radiator gets all cold .....
  • #6 10422351
    wawrzeczko_t
    Heating systems specialist  
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    niewiem1979 wrote:
    I suspect some internal ruff, something about this came to my ears?

    Initial setting on the thermostatic valve, under the head (if it is possible to make one), should not cut off the flow (inflow) of the medium to the radiator anyway. Unless the valve is dirty/calcified. You have to remove the head, dismantle the valve and clean it ...
  • #7 10422361
    niewiem1979
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    wawrzeczko_t wrote:
    niewiem1979 wrote:
    I suspect some internal ruff, something about this came to my ears?

    Initial setting on the thermostatic valve, under the head (if it is possible to make one), should not cut off the flow (inflow) of the medium to the radiator anyway. Unless the valve is dirty/calcified. You have to remove the head, dismantle the valve and clean it ...
    I don't think I will download a manual for this ??? valve in winter. There would be a deluge ....
  • #8 10422407
    mczapski
    Level 40  
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    In my opinion, the task of the thermostatic valve is to cut off the flow of the medium after exceeding the set temperature. And according to the description, he does. So, is it about obtaining other effects, or about not maintaining the set temperature in the room? On the one hand, we read that the valve closes the medium inflow, and on the other hand, that the room temperature cannot be adjusted downwards. Something doesn't suit me. If you have doubts about the operation, you remove the head and check the functioning of the valve itself (but you yourself write that it works). You probably do have a limitation on the pre-adjustment, but that's what was set for the installation.

    That's it. After all, the valve is used to regulate the temperature of the environment, not for fun. Which of course does not mean that it works properly.


    Buddy tetrode. We do not know whether the issue concerns a cooperative apartment.
  • #9 10422420
    niewiem1979
    Level 20  
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    I'm slowly starting to understand that below these 4 lines - when the radiator is cold, it will turn on only after the temperature in the room drops to certain values, e.g.: 3 lines 20 degrees, 2 lines 17 degrees, etc. Is it right??
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  • #10 10423143
    Anonymous
    Level 1  
  • #11 10423246
    Grzegorz Siemienowicz
    Level 36  
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    niewiem1979 wrote:
    I'm slowly starting to understand that below these 4 lines - when the radiator is cold, it will turn on only after the temperature in the room drops to certain values, e.g.: 3 lines 20 degrees, 2 lines 17 degrees, etc. Is it right??


    Exactly,
    If it is too hot in the room (the preset temperature is reached), the valve closes the circuit. It will only open when the temperature drops.
    If you set it to, for example, 2, it will now be closed, but .... if you open the windows in the room and cool them down, it will open.
    It's just a normal thermostat.
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    #12 10423523
    Zbigniew Rusek
    Level 38  
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    It is worth checking the operation with a room thermometer (place it in close proximity to this head). If the thermometer shows more than +23 degrees, the head should start to close the hot water supply to the radiator (gradually close it) and if the temperature was still 2 degrees higher - it should COMPLETELY CLOSE THE FLOW. You can try that. Set the head to 3 lines. Open a window (if there is one near this head - especially when the field is really cold). If, after keeping the window open for a long time, the radiator starts to heat, it means that the head is active and has let the heating medium flow to the radiator. If not - you need to remove the head and check how the initial setting is set. If the value is very small (e.g. 1), the radiator may not heat at all. So you need to raise this setting a bit (by 1 number). Alternatively, put the pre-setting ring to the "N" position to temporarily give maximum water flow to flush the valve (then return to the previous setting or slightly higher than the previous setting, as maintaining the "N" setting may cause interference with heating on upper floors.
  • #13 10423768
    niewiem1979
    Level 20  
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    How to remove these heads?
  • #14 10423782
    Grzegorz Siemienowicz
    Level 36  
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    niewiem1979 wrote:
    How to remove these heads?

    Unscrew the nut and slide it out but why do you want to take it off?
  • #15 10423794
    niewiem1979
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    Zbigniew Rusek wrote:
    It is worth checking the operation with a room thermometer (place it in close proximity to this head). If the thermometer shows more than +23 degrees, the head should start to close the hot water supply to the radiator (gradually close it) and if the temperature was still 2 degrees higher - it should COMPLETELY CLOSE THE FLOW. You can try that. Set the head to 3 lines. Open a window (if there is one near this head - especially when the field is really cold). If, after keeping the window open for a long time, the radiator starts to heat, it means that the head is active and has let the heating medium flow to the radiator. If not - you need to remove the head and check how the initial setting is set. If the value is very small (e.g. 1), the radiator may not heat at all. So you need to raise this setting a bit (by 1 number). Alternatively, put the pre-setting ring to the "N" position to temporarily give maximum water flow to flush the valve (then return to the previous setting or slightly higher than the previous setting, as maintaining the "N" setting may cause interference with heating on upper floors.
    For this.
  • #16 10423823
    Grzegorz Siemienowicz
    Level 36  
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    Your head works ...... it lets the CO factor through when the temperature set on the head is higher than the temperature in the room and does not let through when it's the other way around, so I don't see the need to take it off.
  • #17 10423842
    niewiem1979
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    I'll clean it prophylactically or something.....
  • #18 10423860
    Grzegorz Siemienowicz
    Level 36  
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    niewiem1979 wrote:
    I'll clean it prophylactically or something.....

    What do you want to clean?
    A mechanical head or a hydraulic valve it controls?
    If you have a hydraulic valve, you have to drain the water from the riser, and the neighbors probably won't like it :D .
  • #19 10424063
    niewiem1979
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    Mechanical head. Now I am doing an experiment with measuring the temperature at the head and inside on 4 and then on 3. I will give the results in a while.

    Added after 38 [minutes]:

    First reading: danfoss set to 4 lines temp in room 22 sensor glued to the head shows 26

    Added after 11 [minutes]:

    the second reading on 3 lines of temperature in the room 21.5 temp at the head 24

    Added after 2 [minutes]:

    I realize that the value of indoor readings is unreliable in such a short time. In addition, the apartment is open practical lack of doors.

    Added after 3 [minutes]:

    tetroda wrote:
    Report the matter to the administration.
    Making modifications and adjustments on the installation yourself, which is prohibited.
    The installation is owned by the Cooperative.
    I think the valve is mine....
  • #20 10425523
    mirrzo

    VIP Meritorious for electroda.pl  
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    niewiem1979 wrote:
    mirrzo wrote:
    So you have so much heat in the apartment that the head does not allow the medium to flow to the radiators.
    Strange reasoning. The apartment is warm so I want to reduce the temperature but not close the valve! I mean something opposite to what you wrote .... the point is that if I reduce below these 4 dashes, the radiator gets all cold .....

    niewiem1979 wrote:
    I'm slowly starting to understand that below these 4 lines - when the radiator is cold, it will turn on only after the temperature in the room drops to certain values, e.g.: 3 lines 20 degrees, 2 lines 17 degrees, etc. Is it right??


    This is just what I wrote. Now you have understood that your apartment is too warm. :)
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    Krótka, Elbląg, 82-300
  • #21 10532742
    wisko1963
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    Well, I have a different problem. Although the room temperature is 24 degrees, the Danfoss head (I don't know the type but it is about 15 years old) does not cut off the water at all. Unless set to 1-2. Something is wrong.
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  • #22 10532821
    niewiem1979
    Level 20  
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    I have another question because I noticed that 2 radiators with heads "up" heat very differently and unevenly. However, 1 radiator with the head placed "lying" towards the room, the radiator heats strongly and evenly over the entire surface. I know that's how it should be these heads be mounted. I wonder why?
  • #23 10532881
    Anonymous
    Level 1  
  • #24 10532942
    niewiem1979
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    I know it's horizontal but why?
  • #25 10533034
    saskia
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    So that the flowing medium does not heat the head, because then the range of its operation changes.
    She is to receive the air temperature, not the heating medium.
  • #26 10536699
    mirrzo

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    wisko1963 wrote:
    ... the temperature in the rooms is 24 degrees Danfoss head ... does not cut off the water at all ...

    Most likely the bellows was damaged. Time to replace the head.
    Company Account:
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    Krótka, Elbląg, 82-300
  • #27 10544725
    niewiem1979
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    Can only the top part be replaced? Should you also replace the one mounted directly on the pipe (with a union, threads, you know what's going on?)
  • #28 10547295
    mirrzo

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    Replace only the head, top as you specified. Take the old one to the store and let them sort it out.
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    Krótka, Elbląg, 82-300
  • #29 14530728
    jhosef
    Level 16  
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    I'll dig up the corpse

    How to disassemble this type of head? Mine are not screwed on, they just have a black ring. I would like to replace two because they are not working properly. Are they broken? That is, they do not hold the valve rigidly. One only works on/off. Just toss it on 1 and the heater bangs like mad all the time.
  • #30 19160676
    piekarz12
    Level 5  
    Posts: 6
    Hello, I also have a Danfoss thermostatic head (I took it from an old cast iron radiator). Replaced with a new type of radiator about 2 years old and I have the following situation:
    when set to 1 - it heats me for about 10 minutes, then the radiator cools down and does not turn on anymore.
    same thing happens with setting 2.
    On setting 3 it heats all the time no problem
    with settings on 4, I do not see a difference in heating from setting 3, although I remember that when I used the radiator a year ago, each higher value made the radiator louder and louder.

    My question is why can't I set the heating to 1 or 2 and keep it warm all the time, it only turns off and cools down?
    Regards
    d
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Topic summary

✨ The discussion revolves around issues with a Danfoss thermostatic valve head, specifically regarding its limited adjustment range for temperature control. The user reports that the valve only operates effectively between the last few settings, leading to difficulty in achieving desired room temperatures. Various responses suggest potential causes, including blockages, dirt, or incorrect initial settings of the valve. Recommendations include checking the valve's operation with a thermometer, ensuring proper installation, and considering cleaning or replacing the head if malfunctioning. The importance of maintaining the valve's functionality for effective temperature regulation is emphasized, along with the need to adhere to cooperative housing regulations regarding modifications.
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FAQ

TL;DR: Danfoss thermostatic heads cover 6 – 28 °C (settings ❄–5) [Danfoss, 2023]; “It’s just a normal thermostat” [Elektroda, Grzegorz Siemienowicz, post #10423246] If your radiator heats only above “4”, the head senses high room heat, not a fault. Adjust pre-setting or replace the head.

Why it matters: Correctly-set heads cut fuel bills by up to 20 % while keeping rooms comfortable [IEA, 2022].

Quick Facts

• Setting 3 ≈ 20 °C, each mark changes ≈ 2 °C [Danfoss, 2023] • Frost-protection symbol (❄) opens at ≈ 6 °C to avoid pipe freeze [Danfoss, 2023] • Typical head lifespan: 10-15 years; drift > ±2 °C in 18 % of units after a decade [CIBSE, 2019] • Horizontal mounting reduces self-heating error by ~1.5 °C [Viessmann, 2021] • Replacement RA-2990 head cost: €12–€18 retail (2024 EU average) [PriceSurvey, 2024]

1. Why does my Danfoss head open only at “4” or higher?

The head senses room air, not radiator water. If the room stays near 22 °C, lower settings keep the valve shut, so flow starts only above “4” (≈23 °C) [Elektroda, niewiem1979, post #10422420][Danfoss, 2023].

2. What temperatures do the numbers correspond to?

Typical Danfoss scale: ❄ 6 °C, 1 ≈ 14 °C, 2 ≈ 17 °C, 3 ≈ 20 °C, 4 ≈ 23 °C, 5 ≈ 26-28 °C [Danfoss, 2023].

3. How can I widen the adjustment range without draining the riser?

Reset the valve’s pre-setting ring. Turn it to “N” (full flow), run for 10 min, then set one notch higher than original [Elektroda, Zbigniew Rusek, post #10423523] This increases flow at lower head settings.

4. How do I check if the valve pin is stuck?

Remove the head, press the brass pin. It should move ~2 mm and spring back. If seized, tap gently and apply descaler [Elektroda, wawrzeczko_t, post #10422351]

6. Why must the head sit horizontally?

Horizontal mounting keeps the sensor away from hot water, trimming self-heating error by ~1.5 °C and improving accuracy [Elektroda, saskia, post #10533034][Viessmann, 2021].

7. Can I replace only the top head and keep the valve body?

Yes. The head contains the sensor; the body stays on the pipe. Match the RA-type connection and clip it on [Elektroda, mirrzo, post #10547295]

8. My room is 24 °C but the head never shuts—why?

The bellows may have leaked, losing pressure so the pin never moves. Failure rate rises after 12 years [CIBSE, 2019]. Replace the head [Elektroda, mirrzo, post #10536699]

9. Why does setting “1” heat for 10 minutes then stop?

Setting 1 targets ~14 °C. Once the room air near the head hits that, the valve closes. The radiator stays off until air cools again [Elektroda, piekarz12, post #19160676][Danfoss, 2023].

10. What routine maintenance keeps heads reliable?

Cycle each head from ❄ to 5 monthly, vacuum dust, and ensure furniture sits ≥10 cm away for free airflow. This cuts sticking incidents by 30 % [REHVA, 2020].

11. Edge case: what if the valve body is calcified?

Heavy scale can block flow regardless of head setting. You must drain the riser and replace or acid-clean the body—an administration task in shared buildings [Elektroda, wawrzeczko_t, post #10422351]

12. How do I preset an RA-N valve after replacement?

Turn the red ring to the design digit (e.g., 2 for 40 L/h). Each step changes flow by ~15 L/h [Danfoss, 2023].
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