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Replacing a Pressuretrol with Vaporstat

Hi All,

I have spend the last 2 or 3 hours reading prior posting on this topic. Wow, a lot has been said. And now I know a whole lot more than I did. So I will not repeat info from all of them.

What I really want to know is if some kind soul can point me to directly which exact model I should get for my system. I have a one-pipe system. And I want to set it at about 1 pound. I have at least already figured out that I need one that goes from 0 to 4 psi. And as for how the vaporstat "breaks," I am at a loss to understand what this means. And do I need to know the voltage before I order a particular model? I have added pics of my current pressuretrol. And there are Honeywell vaporstats (currently) at $169 at pex supply, which seems to be about only $50 more than a pressuretrol. I see the Honeywell L408J1017 and the Honeywell L408J1033 at pex at <a href=""></a> but honestly I cannot figure out which is correct for me. So that's the enirety of my question.

(This is an aside, and not the point of my posting, but In case people are wondering, and to cut short long discussion on why I would even want a vaporstat for a simple one-pipe systems, in my case, this is why it makes sense -- I often leave the house for several days and turn down the heat to 50 -- and when I come home and turn it up to 70, the pressure builds up -- and I do not have luck with my current pressuretrol which I think I broke when I accidentally filled my system with water until the water shot out the main vents (a long story that).. And I have several weak spots -- an old joint in the return that is prone to spitting, a union in the main that drips, and an old valve on a rad that leaks -- and all those drips/leaks/spitting starts to happen at about 2 pounds. And my rads fill up nicely at about 1/2 pound. So I need more control.)


  • Incontinent old steam valve

    Those old valve leaks can usually be cured . Most leaking occurs through the packing nut underneath the handle. The packing string in the form of graphite impregnated string can be replaced by unscrewing the packing nut, and digging out the old packing with a pointed tool, and then winding new around the stem of the valve. In my early days with our system, I used some old shoe laces as an emergency fix-those were the days!.--NBC
  • JohnNY
    JohnNY Member Posts: 2,624
    James, it's simple.

    If you need the system to work within 1-16oz of pressure then get that one.

    If you think you'll ever need pressure above 1psi, then get the 0-4psi model.

    Either pressuretrol will work with 24 or 120 volts, so don't need to think about that.

    Also, either model will make or break on rise depending on how you wire it.

    Wiring to R-B will open the circuit when the pressure rises, R-W (reverse-acting) will close when pressure rises.

    An open circuit turns off the burner, a closed circuit allows the burner to fire. Forget about reverse acting controls since they don't apply to your system as far as I can tell.
    Contact John "JohnNY" Cataneo, Master Plumber
    in New York
    in New Jersey
    for Consulting Work
    or take his class.
  • 0-16 oz or 0-4 pound vaporstat

    I was thinking that I needed the 0-4 pound vaporstat. But really, at about 1/2 pound to 3/4 pound all the radiators in the house are toasty-warm. It is a simple 1-pipe steam only 2 story, 1,800 sf house. Does the 0-16 oz have advantages over the 0-4 pound (ie is it easier to set or control)?
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,288
    edited December 2013
    More accurate.

    When the entire range is from 0–16oz., it's a lot easier to adjust it to cut out at exactly the pressure you want than if the range is from 0–64oz.

    Also, there are more than two models of Vaporstat.

    The L408J1025 and L408J1033 models have an SPST switch (actually a SPDT switch with terminal B removed for miswiring compliance). These are fan controls for unit heaters. When the heat comes on, the pressure rises, and the control turns the fan on. This is called a "make on rise" control. This is not what you want, and since these switches are effectively SPST, you cannot rewire them. Also, most supply houses have a strict no return policy for electrical parts, so you won't be able to return them.

    The L408J1009 and L408J1017 models have SPDT switches, meaning that they can be wired as "make on rise" or "break on rise" controls. It is important to wire them correctly. You want to connect the gas control wires to terminals R and B. Terminals R and W are for an optional alarm circuit.

    If you want the 0–16 oz/in² model, you want to order model L408J1009.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
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