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Difficult explaining how this will not work.

Double D
Double D Member Posts: 442

I know it's best to keep everything together in one post but when a system has multiple issues, the thoughts tend to get scattered and some situations go unseen. In looking over a 2 pipe steam system with vacuum pumps and seeing it run, I know the first thing that needs to be done is to lower the pressure. One of the multiple issues is zone control replacement done by others over the summer months. The rooms that have these zone controls have a history of poor heating. The zone location for both past and present controls is on the run-outs leading to the convectors. I'm having a difficult time explaining to the contractor why these zones and their location are not going to work. His only answer was that's where the old ones were. At the present time none of them are working. Seems to be a situation of too many hands in the soup. Here are a few pictures of the zones used. Not full port and definitely very restrictive not to mention bad location altogether.


  • Jamie Hall
    Jamie Hall Member Posts: 23,313
    This is steam? Good grief. First, reduced port valves are bad news, as saturated steam is weird stuff in some ways and will simply condense on passing through the valve -- resulting in little or no steam getting on beyond. Second, there is no provision for condensate on the downstream side of the valve to get back to either the main or a wet return. This is a recipe for hammer.

    If you must use zone controls -- which have other problems as well with varying loads on the boiler -- they must be full port valves and must be dripped on both sides to a wet return.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,532
    As @Jamie Hall said when the valves close you will collect some water on the outlet side. I am assuming the run outs are pitched upward from the main to the radiation. so the outlet side should be dripped. Usually the valve location can be picked to minimize drip lines sometimes they can't

    The valves need to se sized for the EDR of the radiation they feed at a reasonable Cv.

    In this day & age stemfitters are in short supply. Pipefitters that may know water systems doesn't mean they know steam
  • dopey27177
    dopey27177 Member Posts: 887
    The cv indicates that at 2 psig only yields 2400 btus per hour at 1psi steam and at a CV of .29 only 640 btuh will pass thru that valve.

    If the system is a vacuum system the btu value is far less until the system goes into pressure which will happen on the coldest days of the year.

    In this installation a full port valve is needed. The full port valve will supply 2400 btuh.