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Install Zone valves on steam systems

dopey27177 Member Posts: 887
Since this summer and many people think about installing a zone valve or valves in their heating systems I am resurrecting an old discussion for installing zone valves in their heating systems. This is not a cheap install but this method will save problems down the road. If this done on one pipe steam systems a steam trap or traps on each zone is needed as well as a condensate pump. On two pipe steam systems a condensate pump may be required depending on the dimension B.
For safety sake install the condensate pump. Also each zone valve needs a temperature controller.

Taken from my book Steam the Perfect Fluid for Heating and some of the Problems,

See enclosure.



  • Jamie Hall
    Jamie Hall Member Posts: 22,100
    Think twice before doing this on smaller -- i.e. residential size -- systems. Not that it can't be done; it can, though it is by no means simple. If nothing else, you may run into rather interesting overcapacity problems if a large fraction of the system is sometimes zoned off, with significant short cycling.

    It can work well on large systems, but with very different control strategies for the boiler.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Snowmelt
    Snowmelt Member Posts: 1,399
    I am working with an art school in an old section of town, they have a gym and rooms on the side. It’s working with two three inch zone valves
  • Jamie Hall
    Jamie Hall Member Posts: 22,100
    Should work well for that type of system. Be sure those zone valves are full port, and make sure that they have condensate drips on both sides, and at least a vacuum breaker (preferably good sized venting) on the downstream side of the valves. The biggest trick is actually in two parts -- how do you control the boiler, and how do you size it? If the two zones are more or less equally sized, I'd be inclined to size the boiler generously (but not too generously!) -- for the bigger zone alone, and control it with end switches on the zone valves. That way you wind up with a boiler which is not much worse than somewhat oversize for the smaller zone alone, but which still has the capacity (from the dreaded "pick up factor!") to heat both zones are once, when that happens. A balancing act...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Lance
    Lance Member Posts: 257
    Steam is an animal best controlled carefully. I always preferred steam zone valves with potentiometer motors and thermostats to slowly respond to maintain proper steam flow. It is never a good idea to just shut off flow from full on to full off quickly. Let your boiler maintain a steady pressure, let your controls do the rest. One thing I always hated with the new smaller steam boilers is the fact that during a call for water the burner shuts down losing the pressure when heat is most needed, exacerbated by high pressure and quick feed of water.
  • dopey27177
    dopey27177 Member Posts: 887
    The drawings shown depict the proper installation of a zone valve. I have seen many installations where eccentric couplings were used and water collected before the zone valve and banging occurred on heat start up.

    ll the comments made about the installation and controls are the contractors choice, the piping installation as shown is of no choice but is madatory.

    As far as using full port zone valves this should not be considered for every installation.

    A zone valve is sized to supply a given amount of pounds of steam per hour. The sizing of the zone valve is dependent on the inlet steam pressure and the desired outlet pressure. In building heating where the steam system is piped properly 2 psig steam is the maximum pressure. Typically zone valves if full size can be purchased with trim that will reduce the the volume of steam to what is needed at the heating side of the system.

    My preference is to install the reduced size zone valve as it will save a considerable amount of money in installation cost.

    I did not specify controls or safeties in this discussion.

    A primary control other than temperature is a vaporstat on the low pressure side of the system, the vaporstat will close down the zone valve when an over pressure condition occurs and will modulate the steam pressure as needed and that feature is important in one pipe systems where a drop back pressure is needed so vent valves will work properly.

    As far as end switches go that will shut down the boiler that option is controlled by the boiler pressure controller and the buildings temperature controls.

    Jamie Hall who I respect greatly made valid comments but I was showing a proper way to physically install a zone valve and a savings that can be had by using a reduced body size zone valve.

    Typically I don't speak about controls because I have out of the industry more than 20 years and controls have changed, they are no longer KISS school but are sophisticated and complex, many are mini computers and way above my pay grade.