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boiler in a vacuum

Flip Member Posts: 40
When my boiler shuts down after a cycle it pulls into a vacuum, think it may be jacking with my new vaporstat. Any thoughts. Believe it to be an old trane vapor system based on existing piping. new weil-mclain boiler. sized by EDR. No water level problems once system is running. Vacuum holds tight until next cycle. Thanks for input.


  • Fred
    Fred Member Posts: 8,542
    Do you have good/adequate venting on the mains? I would think they should open fairly quickly after the boiler shuts down and that should prevent a vacuum or at least minimize it. Certainly shouldn't be in a vacuum until the next cycle. Is your tstat set up for one cycle per hour?
  • vaporvac
    vaporvac Member Posts: 1,520
    edited November 2014
    That may be true, unless it's a Trane VaporVacuum system, in which case it's DESIGNED to run in a vacuum. That was the premium system, which I also have. By running as such, the steam reaches the rads quickly and keeps producing steam at lower temps. My rads will stay warm for hours without gas and runs sub-atmospherically even when the gas is on after the air has been eliminated. Can you show some pictures of your near piping so we can see if you have an Air Eliminator or one of the other devices they used?

    It's an ingenious system and one well worth keeping. try searching on The Wall library and read up on it. Feel free to ask any questions as it's a favourite topic around here. Colleen
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • jumper
    jumper Member Posts: 2,289
    What's wrong with vacuum? Some say air is needed to push condensate back down to boiler room. But there are systems in which gravity suffices. They're the best.
  • Flip
    Flip Member Posts: 40
    will try and get some pics to post