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Hot water off steam boiler controls

cekseniorceksenior Member Posts: 44
Hi all, My system is a Burnham Independance IN5 Steam boiler with a hot water loop controlling 4 Zones separate from the steam zone. The loop has a pump that circulates condensate through a heat exchanger, a aquastat  and back to the boiler. The zones off the heat exchanger are controlled with an additional pump and honeywell zone control valves. When a zone off the loop calls for heat the circulators come on and the boiler ignites and runs until either the aquastat is satisfied or the room thermostat is satisfied. If the steam zone calls for heat the system will run until the pressurtrol shuts it down off pressure or the room thermostat is satisfied. This is the procedure when the steam and hot water zones call for heat separately

My question is if both steam and hot water loop call for heat at the same time the boiler will stay ignited until the steam system is satisfied even though the aquastat side which normally would shut down the boiler at 180F keeps the boiler ignited. How is this accomplished. What causes the aquastat to be overidden in this situation? Im just trying to figure out how this system is wired. The Burnham installtion manual dosent cover the wiring for this situation.



  • ZmanZman Member Posts: 3,516
    Pressuretol and Aquastat

    It sounds like your steam system is controlled by a pressuretrol as it should be. That system will boil water (212 degrees) until the set steam pressure is reached. The hot water side only needs 180 degree water. When only the hot water side is calling there is no need for steam so the aquastat turns it off at 180.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • cekseniorceksenior Member Posts: 44

    Thanks for reply Carl. Let me try and explain my question another way.

    Lets say the boiler is steaming to satisfy my steam zone. Now 1 of my hot water zones is calling for heat. The water now circulating through the loop is well over 200 degrees and yet the aquastat is not shutting down the boiler.

    My question is how is this wired to accomplish this. Somehow the aquastat is being overided and just the steam controls are in control.
  • ZmanZman Member Posts: 3,516
    Switches in parallel

    The pressuretrol and the hot water aquastat are both switches. If either of them want more heat the will tell the boiler to fire. Your steam system will not heat at all with 180 degree water, so with both systems calling you get 212 at the boiler. If you want to cool down the hot water system during the steam call you will have to either slow the flow to the exchanger or add a mixing assembly.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • cekseniorceksenior Member Posts: 44
    Parallel Circuit

    Thanks Carl that makes the most sense. I haven't been able to locate that elusive extra wiring that would combine them in parallel but I will continue to look. I'm making an electrical schematic of the wiring of my system. I remember a member of this forum commenting on the rats nest of wiring in my system.

    I'm going to use my schematic to install a taco 24v zone valve controller. With help from people on this forum I'm sure Ill get it done right!
  • Ron Jr.Ron Jr. Member Posts: 527
    There should be

    a relay controlling the extra water zones and circulator . The relay should have an extra set of contacts that is also wired into the aquastat and the TT terminals of the boiler . To limit the temperature going into the water zones . Zman is right , if the steam zone is calling you will get 212+ degree water into the other zones if they're on ( had one with 240 degrees from a zone off of a coil ) . A mixing valve is a good idea to prolong the life of the circ and zone valves .
  • cekseniorceksenior Member Posts: 44
    T T terminals

    Thanks Ron Jr. I noticed some extra wiring off a relay connected to the aquastat and circulators. They went to junction box off the boiler with a jumble of other wires. I'll check and see if they go to the boiler T T contacts.
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