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Vaporstat vs Pressuretrol

Hello, everyone. I have a question on vaporstats. I have been reading The Lost Art of Steam Heating and I'm confused on one part.

On page14, Dan states that we need to get about 1 psi at the radiators. So for pressuretrols, he says to set the cut out to 1.5 psi and the cut in at .5.

But, for vaporstats, he suggests 4 oz as the cut in and 10 oz at the cut out. How can the cut out be only 10 oz when we need to get 1 lbs of pressure at the radiators?


  • crash2009
    crash2009 Member Posts: 1,484
    Pressuretrols and Vaporstats

     do not set your pressure.  All they do is prevent your boiler from going over the pressure they are set to.  If you do not have a low pressure gauge, you really have no idea where they are set.  The psi scale on the pressuretrol may or may not be what your pressure actually is.  Your L404F-1060 can be adjusted to shut off the boiler between 2-15psi.  Maybe 2 psi is too much for your system.  Maybe you are set to 3psi or 4psi.  The problem is you don't know, because you don't have a low pressure gauge.  There are many different kinds of vaporstats 0-16 ounce, 0-64 ounce, etc.  Until you can say what pressure is too much its hard to tell you what you need.  I will tell you the same thing they told me.  Start with a 0-3psi gauge, don't buy the wrong vaporstat, take it one step at a time.  Maybe someone can recomend the correct vaporstat.
  • sreja
    sreja Member Posts: 175
    re: Vaporstat vs Pressuretrol

    I think your confusion is due to a misreading of that page.

    What page 14 says is that:  *IF* the building is determined to need 1psi at the radiators, then you set the cut out to 1.5 and cut in at .5 (as an example).

    Different buildings and different setups will need more or less pressure to heat the farthest radiators. If the building needs less pressure then you set your cut outs and cut ins lower.

    Vaporstats are useful because they let you more accurately tune your boiler to work within the narrow minimal psi range that you need.
  • TeachMeSteam
    TeachMeSteam Member Posts: 128
    That must be it

    I see. So, it's likely that I don't 1 psi at my radiators. It's likely that I exceed the required pressure since I am getting hissing at my radiators.

    I'll try to follow crash's suggest and get a low pressure gauge first. I'll give you guys an update when I do that.
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