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Two-Pipe, Air Vented System - Control Issues

The building I am working in has a turn of the century, two pipe, air vented system.  We occupy a few floors.

We are having excessive temp problems in a number of rooms during the winter (85F plus in some rooms)

The building owner/management does not know what they have and in the past have randomly installed thermostatic control valves on the inlet sides of some of the radiators throughout the building. 

Our floors have access issues with the rads, we do not have any thermostatic valves, nor have we been able to play "trial and error" with the radiator isolation valves and air vents.

The building owner's answer to the problem is to install more thermostatic control valves on the problem radiator inlets.

So, assuming we correct the access issues, we currently have the following options:

1) Install thermostatic control valves on the inlet sides of the radiators.  (As steam can enter the radiator from both sides I dont see this as a solution, unless we put thermostatic valves on "both" side of the radiator.  I also think we will still have to play "trial and error" with the air vent.)

2) Install new, manual, accessible inlet/outlet valves and play trial  and error with the air vents.  (Though it is a low tech approach, I am thinking this is the most appropriate course of action).

Any input, suggestions or product recommendations would be greatly appreciated.



  • Steamhead
    Steamhead Member Posts: 14,324
    The proper TRVs

    to use on this system are those that replace the air vent, not the steam inlet valve. You need someone who knows their business. Try the Find a Professional page of this site. 
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,422
    2-pipe misbehaving

    just imagine how the first occupants of your building would have reacted when faced with the temperature control symptoms you have described. not well i suspect!

    it is possible that the air vents on your 2-pipe radiators were added incorrectly to compensate for some other problem, such as bad main venting. i suggest you get a copy of "the lost art of steam heating" from the shop here, and become informed enough to be able to tell the management what to do about the problem. there were a very few radiator-vented 2-pipe systems, so it is remotely possible that your system had them when installed.

    i suspect that the radiators were correctly sized for the heating load in each room when installed, but are now overheating due to bad main venting, or over-pressure, or bad thermostatic control, or.............................................

    some pictures of the radiators [both supply, and return] would be helpful.--nbc
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