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Steam Radiator Inlet Orifice Plates

edbo123 Member Posts: 2
What are you guys opinion on this.
I operate a fairly large apartment complex that gets high temp hot water from a co-gen plant. We use the HT HW to make low pressure steam with steam generators and hot water through heat exchanges. We also have about six old Dunam-Bush Vari-Vac's through out the complex, and a vari-vac control that operates zone valves based on out side air temp. Management wants to install Steam Radiator Inlet Orifice Plates, install TRV's and remove the thermostatic bellows on each radiator in each apartment. I have tried do some google-fu research to see if there is any negatives but keep coming up with the positives. Most of the positives are by the same company that is contracted to do this project. Does anyone have experience with inlet orifice plates?. Any Pro's or Con's. Thanks !


  • Steamhead
    Steamhead Member Posts: 16,832
    The Dunham radiator valves used on Vari-Vacs should already have orificing capability. And you can still get replacement orificing valves.

    You do NOT want to remove the radiator trap elements. These keep steam from getting into the return lines. If steam reaches the vacuum pump, it can damage or destroy it. You cannot depend on orifices to protect the pump.

    Vari-Vac equipment is still being made:

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • ctkay
    ctkay Member Posts: 7
    We have done a few 1000 of TRV/Orfice installs over the years. Call Woody Tunstall, 413 530 9825, He should be able to give some guidance.
  • dopey27177
    dopey27177 Member Posts: 887
    When installing the Dunham orificed valve you need to know the edr of the radiators. The adjustments on the valves is critical.

    The Dunham valves come in 3 models. The two older models are full open at 3.5 turns on the adjustment screw, I don't know what the setting or full open is on the C model.

    Enclosed is the cuts on the Dunham valves.


  • dopey27177
    dopey27177 Member Posts: 887

    Do not remove the trap elements from the radiator traps.
    This a sure way to destroy your Dunham system.

    The Dunham vari vac systems are installed worldwide, I servised these systems for 20 years. Each system originally was set up and tested by Dunham. When the system was were turned over to the customer it ran economically and perfect.

    The steam traps in the system F&ts and rad traps in many cases lasted for 20 years before element replacement were needed. As far as installing TRVs that is a waste of money, what is needed is to have a Dunham rep come in and check the electronic control operation, differential controller and heat balancer .Often the heat balancer location has been affected by an open window or the space has been turned into a storage facility wher there is no heat circulation.

    The heat balancer is the Tstat, in the box there is a coil or fin tube radiator that may need cleaning or a trap that has a defective element. Not much service to do but a service tech can do the adjustments in two to three visits.

  • edbo123
    edbo123 Member Posts: 2
    Thanks for the info Guys.
    Looks like they will not remove the traps just replace them.
    But still install TRV's.

    dopey27177: Thanks for the cut sheets. They did a edr on all the 1200-plus fin-tubed radiators and some still have Dunam metering valves but some were changed out with standard shut off valves for one reason or another. As of now the project is put on hold due to the circumstances.