Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Steam zone valves

Snowmelt Member Posts: 1,279
Thanks to everyone here, I rebuilt the 4 inch zone valve and everything is working. I did a little experimenting so here me out, it’s going to be long but I will give you bullet points.

The old boiler was 300,000 btu it had a leak and going threw 300 gallon of water per day.
When I was there and when I added water like every 20 minutes The Who building heated up

The boiler had no header and used the two risers each one was going directly to each zone.

Boiler was piped with two inch piping one side was two inch for about 5 - 8 feet of two inch then went to 4 inch

Other side was 2 inch for about 40 feet then went to 4 inch.

I waited for boiler to fall apart , replaced it with a 350,000 btu boiler, with all 4 inch going one direction, I also rebuilt the zone valve.

Other direction I did not replace the two inch to 4 inch, I replaced the zone valve.

On the riser I have it at boiler recommended I think it was 3 inch but could of been 4,

If both zones are on only the 4 inch side heats up, if I jack the pressure to 2 psi I get steam to go about 40 feet, then no more pressure on the 2 inch side . But the 4 inch side does make 70 degrees.

Only when I shut the 4 inch zone off , the two inch side gets warm and eventually heats up. The long delay of not doing this earlier was COVID, no classes no money coming in.

Is the answer the steam takes path of least resistance which is the 4 inch side??


  • Jamie Hall
    Jamie Hall Member Posts: 16,068
    Mostly. That 2 inch bit is doing you no favours at all. Not only does it have 4 times the resistance to flow that the 4 inch line has, but worse -- it then expands into the 4 inch line. Now when steam expands into a radiator it condenses we're all very happy -- the heat it releases winds up in the radiator. But what happens when it expands into the 4 inch section? Um... maybe not so much?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 9,184

    Sounds like you made a good bit of progress..

    The right thing to do is to check the EDR of all the radiation on the 4" zone. Then you can figure the pressure drop on the 4" zone.

    Then get the EDR of the 2" zone and using the same pressure drop from the 4" zone figure out what size pipe the 2" zone needs to be. If you can get it close the system will balance itself and the rest can be fixed with venting and the zone valves

    If the pressure drops are widely different it will cause trouble
  • Snowmelt
    Snowmelt Member Posts: 1,279
    Now that sounds like a 2 day job, but I have a friend that likes doing that kind of measuring. The 4 inch side has a condensation pump and a few steam traps. This job is the job I did three years ago which was leaking a lot let me get some pics. Also it’s hard to get a good EDR because it’s a huge ai heat exchanger, I think it was a few row of coils doubles up , seems to heat the room great
  • Snowmelt
    Snowmelt Member Posts: 1,279
    Here are some pics
    This is showing the 3 inch cutting to two inch while the three inch goes to 4 inch.

  • Snowmelt
    Snowmelt Member Posts: 1,279

    Showing the existing set up. 2 inch on both sides not going together at all nothing looks correct but it did heat the building, both sides but boiler had a whole.
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!