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

Difference between Honeywell Vaporstat L408J


You guys have given me great advice about a problem w/ my home's boiler not getting the return water back into the boiler fast enough.  I am reading the lost art of steam heating, and taking the advice I've read here--I want to replace my Honewell Pressuretrol with a Honeywell Vaporstat--but I am not clear on the operating range I should buy--the L408J1009 indicates a range of 0-16oz, while the L408J1017 indicates a range of 0-4psi.

I want the boiler to cutoff at no more than than 2 psi --and possibly less, depending on how low I can adjust it and still get steam in the system--can you advise me which of the 2 models is more appropriate for such an application?


  • Unknown
    edited December 2009
    408J Vaporstat

    It depends on what type of system you have. It you have a vapor system then you should probably go with the 0 -16oz.  I have a crude 1 pipe system so I use the 0 - 4 PSI unit.

    When installing the Vaporstat, keep your old Pressuretrol hooked up and set it up as a high limit safety.  I 've attached some more info on Vaporstats which might be of help to you.

    You also might want to read this thread on vaporstats- especially about Gerry Gill's vaporstat tester  - Rod

  • FJL
    FJL Member Posts: 354
    Vapor System vs One Pipe System

    Are all one-pipe steam systems not vapor systems?  What differentiates a vapor system from a one-pipe steam system?
  • Vapor System

    My understanding is that vapor/vacuum systems are almost always two pipe systems and are specifically designed to run at very low pressure. The Paul System, being a one pipe system from the condensate standpoint, is an exception to this.

    - Rod
This discussion has been closed.