Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

One pipe steam control system?

RayWohlfarth Member Posts: 877
Greetings all I am trying to help a customer with an old one pipe steam system. They were looking at a better way to control each radiator. Currently, they have the Macon EVO Is there any other control ideas where they can use a wall mounted thermostat? I saw where they have one with a remote bulb. Any ideas?
Ray Wohlfarth
Boiler Lessons


  • Jamie Hall
    Jamie Hall Member Posts: 15,742
    Argh. Controlling one pipe steam is... difficult. Hate to admit it.

    The first step is to make sure the system is as well balanced as it possibly can be. Mains vented adequately so the radiators get heat at more or less the same time (in a big system this is hopeless, of course, but within a few minutes of each other anyway). Then adjust the venting on all the radiators so that they heat their respective spaces as intended (this does not mean that all the spaces are the same temperature! Bedrooms, for instance, are often wanted cooler!).

    Then... the only place to go from there is thermostatically controlled radiator vents [actually not true -- see next paragraph]. And yes, there are some which have remote bulbs. There has been a lot written on this on the Wall -- and other places! -- but the bottom line is that a TRV can reduce the heat output from a radiator. It can never increase it. If you start a boiler cycle with the TRV open, the radiator will start to heat; if the TRV then closes at some point in the cycle, the radiator will continue to heat, but only at the rate -- more or less -- it was heating when the TRV closed. If the TRV is closed at the beginning of a cycle, the radiator won't heat much if at all, though if the TRV then opens during the cycle, the radiator will start to heat for the rest of the cycle. In some situations having a vacuum breaker on the vent line may help control, as it allows air in to the radiator even with the TRV remaining closed.

    Close control also requires that the boiler cycle off fairly frequently. It doesn't have to stay off long, just long enough for the system pressure to drop to zero gauge, but it does have to shut off from time to time. There are a variety of strategies to do this -- perversely, there are some probe type low water cutoffs which will do it for you, though that isn't the reason they do it.

    It is also possible to place a zone valve on a steam main to cut off a whole part of a system. This is not quite as simple as it sounds. First place, the valve must be a full port design, such as a motorized ball valve. Second, some provision must be made for the condensate -- and any condensate on the cut off side of the valve as well as the live side. Not impossible at all -- intelligently placed loop seals and condensate wet returns will work well, provided the pressures are kept low enough and the vertical dimensions allow it -- but thought has to be given to this. The motorized valves can be controlled by any thermostat you like, of course.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • RayWohlfarth
    RayWohlfarth Member Posts: 877
    Thanks Jamie Sounds like you have been there done that
    Ray Wohlfarth
    Boiler Lessons
  • mattmia2
    mattmia2 Member Posts: 2,869
    I think there are also 24vac heads for TRVs, although powering them and wiring them to a thermostat seems like it would be a problem.

    Also keep in mind that the boiler might not be particularly happy about you taking away a significant amount of the radiation that was condensing its steam.
  • ethicalpaul
    ethicalpaul Member Posts: 2,955
    Have them put a nice blanket on any that heat their spaces too much. No muss, no fuss, easily adjustable, can't break, keeps the customer involved in their own comfort.
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
  • RayWohlfarth
    RayWohlfarth Member Posts: 877
    Thanks @mattmia2 I will look into that
    @ethicalpaul LOL Thanks for that tip
    Ray Wohlfarth
    Boiler Lessons
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 475
    If your customer is willing to go the "set it and forget it" way, install adjustable vents, like the Vent Rite#1 (fully shut to #5) and Heat Timer Varivalve (#5 and larger). That should cover almost any situation. It may be easier than swapping MoM orifices or complete radiator vent valves. (As an alternate, MoM orifices are available separately from the valves, but you have to call the company...they sent me some for free.)

    Get a wireless thermostat, like the Honeywell, so they can locate it anywhere in the house they want to balance everything out. Some can be remotely operated with an additional device to connect to the internet. (Good option for a landlord that doesn't live in the house.)

    Tweaking individual radiator vents can upset the balance among the rooms and may only make things more complicated throughout the seasons.

    Dan's advice is to get the coldest room in the house satisfied first, then balance the others. Some guys on HH don't advocate this approach and depending on your situation, it may not be preferred.

    Putting the thermostat there is a good starting point and if wireless it can be moved around to take into account effects of sun, wind, windows, doors, and other heat sources (like kitchen stoves, fireplaces, heating system through pipes, chimneys, etc.)

    If the occupants are obsessive tweaker, this may not work.

    By the way, is this a single family, multi-story house or something else?

    Good luck.

    Let us know.
  • RayWohlfarth
    RayWohlfarth Member Posts: 877
    @SteamingatMohawk Thanks for the good ideas The building is an old one at a local college The building was built around 1900
    Ray Wohlfarth
    Boiler Lessons
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 475
    My pleasure. I have limited experience, the guys with thousands of posts are the real experts.
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,355

    I have limited experience, the guys with thousands of posts are the real experts.

    Not necessarily. I have 2,314 posts, but most of them are dumb questions. :D
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 475
    It takes an expert to separate the wheat from the chaff....lots of chaff.

    What bothers me about some of the posters is how wrapped up in technology they are, thinking the control system is like geeking a computer motherboard and all the other stuff that makes a computer work.

    I fear they don't have an appreciation for the stored energy in a steam system. That's why I give my liability/risk assessment sermon so often. Plus somewhere in HH I related how a house with BB hot water I owned in Delaware had a failure that sent the expansion tank through a wall hitting another wall instead of going out into the street. So I learned a big lesson the hard way. Nobody got hurt.
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!