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Zoning two rooms on one radiant slab

mostlybirch
mostlybirch Member Posts: 17
in Radiant Heating

Hello, I have an insulated 40x16 slab in Fairbanks, Alaska for the garage and boiler room. The boiler room is an enclosed and insulated 16x10 section of the garage slab. Four total circuits of 1/2" pex on 9" spacing, 6" around the perimeter, with one circuit in the boiler room, all loops being close to 225'.

I am thinking that because the boiler room is a smaller area and more insulated that if I kept them on one zone the boiler room would settle into a higher temperature than the garage at any given setting. If my goal is to maintain a ~50F in both the garage and boiler room, is this something I can get somewhat close through the balancing valves? ie: reduce flow to the boiler room. Or will I be chasing my tail and should build two separate zones with zone valves.

Right now the plan would be to keep both rooms on one manifold.

Thanks

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,695
    edited December 2024

    That will work IF the loops in the slab do not feed both rooms. Are you sure that only one of the loops is in the Boiler Room and all the other loops are in the Garage area only?

    This loop system will not be able to be zoned the way you want it.

    Screenshot 2024-12-28 at 3.01.03 PM.png

    …. Because every loop in the system goes thru the boiler room floor

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • mostlybirch
    mostlybirch Member Posts: 17
    edited December 2024
    circuit.png

    Correct, the circuits are separated by an insulated wall and the manifold is located on that wall.

    shown diagram for illustration purposes, minor differences in final design

  • hot_rod
    hot_rod Member Posts: 23,773

    buy a radiant manifold that you could add actuators to later in if you need more control

    what type if boiler will you use?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,695
    edited December 2024

    Then you can use one manifold and try this idea. set all the manifold flow rates manually, as needed to maintain the temperature wanted in the garage. Then on only the loop that is in the boiler room, add a two wire zone valve actuator. Put that on a thermostat in the boiler room, no end switch needed. The function of the boiler rom thermostat will be to close off that loop only if the boiler room has sufficient heat while the garage thermostat operates the pump and boiler in the normal configuration.

    Screenshot 2024-12-28 at 3.47.59 PM.png

    This way the boiler and pump only runs when there is a need for heat in the garage. If the boiler room is also cold, that loop will be allowed to operate. If the boiler room is up to temperature, then the valve will close and more heat will be available for the garage, and the boiler room will not over heat.

    I call this type of thermostat operation an Allowance thermostat, as opposed to a full function thermostat the operates more than just a zone valve

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    mostlybirch
  • mostlybirch
    mostlybirch Member Posts: 17
    edited December 2024
    https://forum.heatinghelp.com/discussion/comment/1830388#Comment_1830388

    I purchased a Rehau manifold with balancing valves. I believe I can add actuators to that unit.

    Boiler is a Toyotomi OM-128HH. "Semi on-demand" oil-fired which has an internal 5 gallon heat exchanger. Rated for hydronic and domestic use. Seems to be commonly used here in Alaska but not elsewhere. Smallest sized oil boiler I could find. Small heating requirements, domestic hot water in the attached yurt and 640 sq ft of slab heating in the garage.

  • mostlybirch
    mostlybirch Member Posts: 17
    edited December 2024

    Thank you this was helpful and the direction I was heading. I think I will setup on one manifold and balance valves and see how "unbalanced" the heat distribution is between the two rooms and add an actuator on boiler room thermostat if necessary.

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