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Two-Speed Hi and Lo Fire Hydrotherm

Is it possible that Hydrotherm  manufactured boilers that were intended to have both high and low fire (two stage gas valve) and a two-speed draft inducer, with separate pressure switches for high and low fire, and yet only a single pole aquastat  and no way to control the two speeds and firing rates? I have seen this configuration twice, maybe three times. The wiring diagram says "Boiler will operate at high fire only".  WTF? These were made in about 1985 or so. Some other versions of this boiler actually work with both high and low fire.

Comments

  • Tim McElwain
    Tim McElwain Member Posts: 4,481
    Do you have

    a model and seriel number for the boilers? I seem to remember that these were originally designed to be two stage but some were shipped as single stage only. What are they using for a gas valve and relays? 
  • Plumdog_2
    Plumdog_2 Member Posts: 873
    Called the local Hydrotherm Rep

    and he thinks that a large number of these were shipped without a two-stage aquastat, and intended for use as on-off boilers. They are equipped with a two-speed fan, a pair of honeywell relays like a R 8225 , a huge lo-fire pressure switch, and a smaller hi-fire pressure switch. The gas valve is two-stage, both stages work, but the hi-fire is brought in by the hi-fire pressure switch. And the thing only runs on high speed. A waste of parts. They are discontinued, some parts no longer available (pressure switches). Anyhow, this house is right near, if not IN, the big wildfire going on now in Colorado.
  • Plumdog_2
    Plumdog_2 Member Posts: 873
    Model Number

    Sorry, it's a H-1 165C If I remember
  • Tim McElwain
    Tim McElwain Member Posts: 4,481
    Yes I am sure they had

    plans for those to be two stage but over manufactured and sent them through as single stage. When you replace parts replace with single stage controls they cost less.
This discussion has been closed.