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boiler cold start pressure

kevin_64
kevin_64 Member Posts: 1
in THE MAIN WALL
Why does a hot water boiler cold start pressure start at 12 psi?

Comments

  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    typical feeder setting

    Thats where the typical boiler feeder is set from the manufacturer. Theoretically 12psi, will feed water to a height of approx 28ft - within the operating range of a normal 2 story residence. The typical residential boiler is rated for a max operating pressure of 30lbs. With a properly sized expansion tank, when the system is operational and the water is heated, you will see operating pressures rise, typically somewhere between 16-22 lbs.

    If the pressure was set lower, and you had high water temps, you could potentially have significant air issues including flashing.
  • Toddid Goldsmith's
    Toddid Goldsmith's Member Posts: 77
    Cold start pressure

    Glen you are right on with properly sized expansion tank.That is something that is a big issue with cold start. Tank manufactures make it quite clear to have a properly sized tank. Instructions tell you to bring system to normal operating temps then readjust the pressure,Then on a nice warm day, the system coos down, and takes us right back to the same set of conditions we started with when we took the tank out out of the box, and installed it.
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