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What's the best TRV for one-pipe steam heat?

Jeremy_16Jeremy_16 Member Posts: 113
Hi All,

I'm looking to install some TRVs on radiators in a one pipe steam heating system. We manage a 4 story apartment building in Boston where the back of the building is facing south and gets a lot of direct sunlight. The rear apartments are almost always warmer than the front, north-facing apartments (aside from some cloudy/stormy days). Some of the rear apartments have TRVs in them, but others have vent-rite vents that replaced some of the TRVs as they stopped working.

The TRVs we have are pretty old and made by a company called "Flair Mfg Corp" and a few are made by "Honeywell Braukmann". Attached are a few pictures of the TRVs. I'm not sure if any of these current TRVs have vacuum breakers; do they?

After reading Dan's book "The Lost Art of Steam Heating", I see he mentions Danfoss RA-2000 (which has a vacuum breaker) as a good TRV for single pipe steam heat. When I go to look this product up online I see manuals for it, but no where do I find that exact vent (RA-2000 - I see other Danfoss products though). Do they still sell the RA-2000 or is there maybe a better version made by Danfoss out now?

I'm just wondering what people recommend for a good TRV with a vacuum breaker to prevent over-heating. Should I replace my old TRVs or just buy new vents for them (any advice on where to buy online or near Boston MA)? Any suggestions would be much appreciated. Thank you.



  • Jeremy_16Jeremy_16 Member Posts: 113
    Hi Abracadabra,

    Funny, I saw that link before but only saw the "Danfoss 013G0140" didn't see the description that mentioned RA-2000.

    I could be mistaken, but it appears the link you provided is only for the body of the TRV, right (and doesn't include the vent)? Does a vent need to be purchased separately? Do you or anyone else recommend a particular vent to go with it?

    Is there anywhere where I can purchase the complete product in one place? Thanks.

  • KC_JonesKC_Jones Member Posts: 4,401
    There are 3 parts you need for the Danfoss. The part that was linked to and a vent of your choice (vertical vent) and the thermostat operator. It doesn't come with the thermostat because depending on the application you have several choices. Some are remote thermostats for when the rad has a cover others are direct mount for when it's open. The RA-2000 number is the thermostat operator as far as I know. From everything I have read and experienced they are the best.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Jeremy_16Jeremy_16 Member Posts: 113
    Hi KC_Jones,

    Interesting. I thought from the picture that the Thermostat operator was included. Is that gray head in the picture a dummy part? (see link again -

    Judging from the links that popped up on the side of the first link it would seem these 2 are viable options:

    Is that correct?

    KC, do you have the Danfoss TRVs on a lot of your radiators? Did you buy Danfoss vents or another type?

    There is only 1 review for the Danfoss vent on supplyhouse website and it's not very good. No reviews at all on Amazon. Does anyone recommend that vent or another one to go with the Danfoss Valve body?

    Also, does anyone know how long the body or thermostatic operator last? I know vents need to be changed every so often, but this unit is expensive when you add up the 3 parts. I have several radiators that will need them so it could add up to hundreds or thousands of dollars. It would be good to know if people have had these TRVs for a while without needing to replace them. Thanks.

  • ChrisJChrisJ Member Posts: 10,860
    edited October 2015
    The grey cap isn't a dummy part, but rather a manual knob. You can operate the valve manually if you wish. The "operator" you buy that snaps on, is an automatic operator.

    I'm using a Gorton 5 on one TRV and a Gorton 6 on the other I think, though they both may be 5's I can't remember. You just need to buy the gold painted straight ones.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • KC_JonesKC_Jones Member Posts: 4,401
    I used to have them on 2 rads, but in my case I was able to straighten out my venting when I installed the new boiler and eliminated them. You can pretty much use any straight vent on them, but be aware the TRV offers some resistance itself so you may need to use a slightly bigger vent than you think. In my opinion the TRV doesn't eliminate the step of balancing the venting just helps stop overheating. If you vent it too slow you won't get enough heat (I know from experience on that). They can't call for heat they can only shut it off so to speak. Just out of curiosity have you tried balancing the system without them?
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Jeremy_16Jeremy_16 Member Posts: 113
    Hi guys,

    Let me respond to both of you:

    ChrisJ: Thanks for the tip. So if I buy the automatic operator, will it go in the same place as the manual one (meaning I have to remove the manual one in order to put the automatic one on)? Thanks also for the tip about the Gorton air vents. I didn't even know they made the straight type vents for radiators.

    KC_Jones: Yes, I have done a lot of work on our heating system. We have an MPC platinum heat timer controlling the building with an internet communication panel. I have temperature sensors in every unit so I can see the temperatures online (this helps a lot). I have tons of Main venting in the front (about 4 gorton #2s per main on an antler) The back of the building has less main venting but still a few Gorton #1s etc per main (back of building has shorter runs for the mains). In the front I also have Hoffman #75s in the top floor apartments on the top of a few risers (a master venting approach).

    I used Gerry Gill's and Steve Pajek's "Balancing Steam Systems using a vent capacity chart" to figure out the optimal venting ( -This is a very cool resource by the way).

    The problem is the sun though. Even if I perfectly balance the system, the sun still heats the rear units about 4-5 degrees warmer.

    I also have 1 inch thick insulation on the header of the boiler and 1 inch thick insulation on all pipes exposed in the boiler room. There are some mains going to the front of the building that do not have insulation but they are inside the walls buried. So there is not much I can do there. I'm sure it would help speed up the steam if they had insulation on them, but I'd have to rip open walls to get to them. I'm not sure if that would be a worthwhile endeavor. Would it?

    I looked at all of the temperatures in the front and rear apartments on a day before I even turned the heat on in the building. There was a 4-5 degree difference in temperatures between the back units and front units (solely due to the hot sun shining into the back). Even if I could balance the system to account for this, I would run into trouble on a cloudy day (or those weeks when you have a few of those days in a row). Sometimes when we don't have sun for a few days the back units get a little cooler. That's why I figured TRVs would really be the best possible solution for this issue. That way I can speed up all of the mains to the max using proper venting, but the radiators in the rear of the building will stop venting once they reach, for example, 70 degrees. That way the front will still get heat, but the back won't over-heat.

    I'm not sure what else I could do, but if you have any ideas, please let me know.

  • SteamSteam Member Posts: 45
    Macon also makes TRVs. Their model is the Macon OPSK for single pipe steam. It comes in one complete package, without the need to order separate parts like the DanFoss TRVs require.
  • BioBio Member Posts: 277
    I agree, it seems to be a more of a solid unit, the vacuum breaker s on top out of the condensate way
  • Jeremy_16Jeremy_16 Member Posts: 113
    Steam or Bio: do you have the Macon TRV on any of your radiators?

    Has anyone else used them?

    Does having the vacuum breaker on top make a difference vs the bottom? Is having it on the bottom more likely to get it filled with crud? Is that the thought?
  • SteamSteam Member Posts: 45
    I will be installing the Macon TRV during the season. The Macon TRV already has a tamper proof feature on the assembly. You have to buy a separate operator on the DanFoss TRV.

    The vacuum breaker on top is common sense. Did you ever see a deaerator with an upside down vacuum breaker located where condensate and crud can affect it's operation? I haven't. What's also a great feature is to offer a complete package, instead of different parts that should be able to be ordered for replacements.

    I've chosen the Macon based upon it's design, and also recommendations from plumbers who've used them. The only true test can be done side by side with a Macon OPSK installed on one radiator, and a DanFoss RA2000 installed on another. See which one does the job and outlasts the other.

    Good luck,
  • ChrisJChrisJ Member Posts: 10,860
    edited October 2015
    The Danfoss is designed so the vacuum formed in the system during shutdown automatically pulls condensate out of the vacuum breaker. It's actually a very good design and has served me well even running well below an ounce of pressure.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • LionA29LionA29 Member Posts: 254
    @steam how is the TRV working out for you?
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