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high water cutoff?

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JaymeHart
JaymeHart Member Posts: 66
in Strictly Steam

Is there any way to do a high water cutoff?

I have a single pipe steam system with 1 radiator on a hot water loop, fed as a closed loop pumped system (no heat exchanger). my installer didnt include a bypass/mixing loop (long story there, dont think they understood the problem of flash steam), so I piped it in myself using black pipe.

I made one mistake with the black pipe mixing loop, and assumed a union joint could accomidate a 1/2" difference in joining position, because I didnt have a 3 1/2" pipe and used a 4" pipe. That caused a bit of air to get into the hot water gravity loop during operation, and ended up draining water into the boiler, overfilling, and some quite dramatic cavetation issues. Thank god I was home and caught it in time.

but now I am paranoid. I can fix the air leak, pipe it proper plumb and straight, but I worry about a small risk of another leak and sudden boiler overfill.

I could definitely mitigate with a proper heat exchanger, expansion tank, zone separation, etc. I very well might do that during the summer to fix and be 100% confident going forward, but

is there anything like a high water cutoff I could use now, through the season, just to keep running as in and not worry?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 27,060

    I'm not really aware of one, though I can think of several ways to MacGyver one. However… depending on what pressure control you have and how it is set, it will act as a surrogate.

    Now most systems wind up with the cutoff around 1.5 to 2.0 psig, which is a bit high for the purpose (2 psig is 56 inches, which would be well up into the mains and into some of the first floor radiators!). But… if you run a vapour system, the cutoff will be around half a psig or less, and the boiler will shut off with an overfill of only 14 inches…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JaymeHart
    JaymeHart Member Posts: 66
    edited January 30

    i have a 0-4psi Vaporstat set at just below 1psi. i think I will push it down to 0.5psi given what you state above, and that past like 0.25psi it is just in runaway pressure building anways.

  • Jamie Hall
    Jamie Hall Member Posts: 27,060

    Then assuming that the vapourstat cuts power to the automatic feeder — that depends on the wiring — you can't overfill more than two feet or so above the vapourstat.

    Even if it isn't, you could, depending on the particular vapourstat, use the set of contacts which closes on pressure rise (most have a set) to actuate a relay which would cut power. Might take a bit of creative wiring, but wouldn't be that hard to do.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JaymeHart
    JaymeHart Member Posts: 66

    thanks. that is helpful advice.

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