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Out of service old air operated thermostat system- junk it?

john58 Member Posts: 7
I maintain the hydronic  heating system in a small christian grade school, formally an old public school building.  The Honeywell air operated thermostat system has not worked for years. A single thermostat in the hallway controles the boiler temperature. The circulator runs continuously. The teachers have some control of classroom temp by manually turning on and off the blowers in the room unit heaters.  The modernization of the controls already done consists of  installing a programmable thermostat in the hallway and a triple function aquastat to control the circulator pump. I need some expert advise. As a retired guy heating has not been my field of expertise.  Should we tear out the air compressor and other controls?  It appears to me it would be prohibitively expensive to get this system working again with thermostats in every room. I would like some confirmation that I am on the  right track in my thinking as I have to answer to the school board with my advise. Thanks for your help. John Gantz.


  • GBriggs
    GBriggs Member Posts: 15
    Pneumatic Controls

    HI John,

    Pneumatic controls work very well if maintained properly. You could have your hands full if the system has not had annual service. If the air compressor has pushed water and oil throughout the systems main and branch lines most of the controls will be gone. All system controls and parts are available and most can be rebuilt. Day night controls can be added easily. Now if the system has been let go an onsite review would be necessary. Most schools did have room control making it a very zoned system which helps with the energy usage.
  • DavidK_2
    DavidK_2 Member Posts: 124
    I'm not an expert,

    But I work in a building with these air based thermostats. Unfortunately only in every other room, and not functioning very well. In my building the thermostats are supposed to control mixing of warm (or cooled) air with ambient temperature air. I assume in your building they would control the water temperature in each room? Our system suffers from poor maintenance - the mixing valves are sticky and sometimes they get stuck in a bad place. They are also not always labeled properly.

    I think the first thing you need to do is figure out what these thermostats used to control. And figure out if there is a benefit from being able to control it again. Controlling temperature with one thermostat in a hallway doesn't seem like it would be very comfortable. If your teachers occasionally use an open window to control heat there might be alot to gain by getting the old system to work again. Or maybe at least being able to automate the turning on and off of circulating fans (perhaps with a simple thermostat and relay in each room?)

    If you do not feel comfortable telling the board what to do, you might suggest they hire a consultant before they do something you all might regret later.
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