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Vaporstat Settings

How do you determine proper Vaporstat settings? I just had one installed (current settings are cut in at 2oz and cut out at 6oz, I believe). There are nine rads in my system. Peerless boiler.

I was reading pg 14 of "The Lost Art of Steam Heating" and Dan indicates a cut in at 4 and cut out of 10. Should I interpret that to mean everyone who has a vaporstat should use those initial settings?

Since I'm a layperson, if I raise the cutout from 6oz to 10oz, what will this really do? Keep the boiler going longer? Burn more fuel?

Any help would be greatly appreciated as there isn't a lot of info available on the web.

Thanks in advance.

Fred Clough


  • Firedragon_4
    Firedragon_4 Member Posts: 1,436
    The cut-out should be

    at 16 oz. and the 'DIFF' should be set at 12 oz. The Cut-out on the L408 is also called the 'Main'.

    JMO, but it works 98% of the time for me with new or old boilers.
  • Mitch Henderson
    Mitch Henderson Member Posts: 4
    Vaporstat pressures and models

    I have a new Weil Mclean residential SGO boiler with a Honeywell pressurestat I can't control well. Need a Vaporstat. Any recommended models? Also, is Dan's 10 oz/4oz cutout/cutin setting right? Won't there be too much cycling of burner? At about 1.9psi/.9 psi, I'm getting 5-7 cycles in this late fall weather. Maybe I need to cut back on burner fuel rate too?
  • Boilerpro_3
    Boilerpro_3 Member Posts: 1,231
    It depends

    Many vapor systems are not to be operated above 8 ounces because it will cause steam to enter the returns...so your high setting should not be above 8 ounces. However other vapor systems can be run higher. So it really depends! More info on what type of sytem it is will help, or better yet a site visit from a truly knowledgable steam contractor would be good.

This discussion has been closed.