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Thermostatic Radiator Valve for One Pipe Steam w/ Radiator Cover

We are looking to install TRV (likely a Danfoss) on a radiator in a one pipe steam system. The radiator has a well-ventilated wood cover that has about 3" of space from vent hole.

Are there any options available to install the TRV without cutting open the cover? It appears the only acceptable Danfoss valve for one pipe steam heat is 013G0140, which is completely straight and does not allow the operator or attachment on a remote sensor to be angled. The standard Valve Mounted Dial looks like it's about 5" with the valve, while the attachment for the remote sensor looks like it will be about 4" with the valve.

Any ideas on this, or shall we get to cutting open to cover to accommodate one of these?


  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    If you need the system notch out the cover . I would

    There was an error rendering this rich post.

  • nicholas bonham-carter
    Why do you wish to install a TRV? Is the room overheating?
    What sort of vent is on the radiator, and mains?—NBC
  • retiredguy
    retiredguy Member Posts: 907
    The thermostatic part of the TRV can not be located inside the cover/enclosure. It has to sense the ambient air in the room to work correctly. I would only use these TRV.s as a last resort and only on rooms that do not have the thermostat.
  • racingkaherva
    racingkaherva Member Posts: 6
    Thank you for the comments. The room in question is the first room on the line, directly above the boiler, and overheats when the boiler runs a lot on very cold days. I had to put a variable vent on the radiator because I was changing from 6 to 4 vents, depending on how much the boiler was running.

    The room does not contain a thermostat. The mains are properly vented. This room is the outlier in the system. It just gets slammed with steam on the coldest days.

    As mentioned, the enclosure is very well ventilated (it has wood slates spaced quite far apart). I can also use a remote sensor/dial for the TRV.
  • mattmia2
    mattmia2 Member Posts: 9,670
    edited September 2020
    I think someone familiar with all the pieces in the danfoss catalog can put something together that will fit in your enclosure and will allow you to extend the dial and sensor outside of the cover.
  • dopey27177
    dopey27177 Member Posts: 887
    Here two things can be tried. Both at same time.
    install the smallest vent valve that can be purchased and paint the radiator with silver high temperature paint.

    The paint will drop the output of heat from the radiator anywhere from 15-25%.

  • racingkaherva
    racingkaherva Member Posts: 6
    Thank you, both!
  • gfrbrookline
    gfrbrookline Member Posts: 753
    I agree with @dopey27177 , install a Gorton No. 4 on that radiator and paint it silver. TRV's on 1 pipe are more trouble than they are worth from my experience. They can take a hot room and turn it into the coldest room in the house since you miss heating cycles.
  • nicholas bonham-carter
    An old blanket, draped over the radiator, under the cover, will also moderate the heat—NBC
  • ted_p
    ted_p Member Posts: 65
    edited September 2020
    Danfoss makes an adapter that might help.

    I've used more than a few of these:

    Below are two pics showing one of these installed on a radiator with a Danfoss 013G8018 (3/4" Side mount angle valve) where I had side clearance problems, first without, then with 013G8250 operator (combined dial/operator/sensor).

    Here's a radiator sporting the same Danfoss 013G8018 valve, with the 013G8250 operator mounted directly on the valve, for comparison.

    If it's too tight for that, I don't see any reason not to come out of the radiator with an 1/8" nipple and a 90, mounting the valve so the operator points up, and use an angle vent (which is most likely the type of vent that you already have).

    You can rotate the valve to point the vent in any direction that you have space.

    I know that Danfoss says that the operator must be mounted horizontally, but that's actually true only for the ones with the sensor in the valve-mounted dial, like the 013G8250, and those aren't suitable for use in an enclosure anyway. Any of the operators with remote sensors will work fine regardless of the direction that they're pointed in.

    Another thing that Danfoss doesn't tell you is that the 013G8252 (which is the least expensive option with a remote sensor) works fine in enclosures, as long as you don't mind removing the enclosure when you want to turn the dial.

    013G8252 Valve Mounted Dial w/ Remote Sensor

    I put one on the giant (6 tube x 38 section) Arco radiator in the lobby of my building, and it works like a champ. In that location, the inaccessibility is actually a virtue; keeps it out of sight and reach of random twiddlers. ;)

  • racingkaherva
    racingkaherva Member Posts: 6
    Thanks so much, @ted_p. That is incredibly helpful. I didn't realize you could turn the valve like that and still have it work in a one-pipe steam heat system. That changes everything. I think I can fit that in the radiator cover and put the sensor outside of it with no issues. Thank you!
  • Gordo
    Gordo Member Posts: 857
    That 013G1350 Danfoss angle adapter is a nice bit of kit to get you out of trouble, for sure. We've used it a fair number of times. No other TRV manufacturer has anything like it.
    The only issue is the plastic. I was told by our excellent Danfoss rep, Bill Boss, that the white plastic they use to make it does not hold up to the heat as well as the gray plastic (seen at the base of the direct mount actuator) . That begs the question, why don't they make that otherwise excellent adapter out of the more heat resistant gray plastic? You'll have to ask them $.
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