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TRVs in a vapor system

Okay All of you old steamheads out there, got me a job I just finished up, boiler replacement on a 1937 cast iron fin tube installation, replaced all of the old orifice traps and flushed the wet return, so the system is working the way it was designed to. Now here is my problem, this used to be apartments that have now been converted to condos, but I convinced the HOA that all work on the steam system, in anyone's unit was a shared responsibility, can't separate out the components from the whole, the lower units have been toasty but not too bad, but the two upstairs units have been roasting, according to the women who live there, so my question is, two pipe system,orifice traps (Hoffman 17c), can I add trvs to the supply pipe and an air/steam vent to the radiator and have this work as I have in mind, which is some control over the individual radiation, Thanks, I look forward to the answer. Mike Miller


  • Jamie Hall
    Jamie Hall Member Posts: 19,968

    or you might be able to get away balancing the thing by just partly closing the inlet valves in the offending rooms.  I don't see any need for an additional vent on the radiator, though.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • TRVs & Vacuum

    If you go with TRVs, be sure to note Dan's warning on page 147 of "The Lost Art..." on radiator traps and vacuum.

    I'm sure each owner would like having the individual control of the heat in their unit that the TRVs would provide.  How is the thermostat situation controlled? From an economical operation stand point you might want to take a look at a Tekmar 279 with multiple sensors.

    - Rod
  • Mike Miller_2
    Mike Miller_2 Member Posts: 17

    Jamie, these are cast iron fin tube behind covers and there was never any supply side valves installed, that is why I was wondering about the TRVs, if we were going to have to put in the labor to install valves, they might as well do the thermostatic thing, and Rod, I had read that by Dan Holohan, which is why I was thinking about putting an air/steam vent in between the TRV and the orifice trap. The system is controlled by a single thermostat in a hallway that has no radiators, it really sucks, but I don't know about the Tekmar, all I really need here is a simple on/ off switch, (thermostat), it just needs to read real temp. I cannot figure out another way to separate radiators, except for mechanically. Anyway, I just am trying to come up with a more efficient way to control these radiators other than just a globe valve on the supply side, but that idea is elegant in its simplicity, thanks Mike Miller
  • Jamie Hall
    Jamie Hall Member Posts: 19,968
    But read on...

    it isn't that you have to install a vent or a vacuum breaker on a radiator with a thermostatic trap and a valve or a TRV.  It is that if you DO install a TRV, do it at a time when the system is off and cold (that remark is on page 148 of Lost Art).  Then all will be well.

    The thermostat would be in a place where there is no heat.  That is not ideal... can it be relocated to one of the units which does have heat?  Although the present location isn't bad in one way: valves (TRV or otherwise) can only reduce the heat going into a space, so any thermostat should be in the hardest space to heat!  I still think that I would be inclined to buy ordinary radiator valves and install them on the fin tube, and get the folks in each unit to adjust them to their satisfaction.  Just make sure that the units near the thermostat don't get shut off!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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