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SR503 to HydroStat 3250 Plus Wiring

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Richtdow
Richtdow Member Posts: 22
I'm confused on wiring a SR503 to a Hydrostat 3250 Plus for cold start. The wiring diagrams for each seem contradictory. I have a setup with three zones and circulators. HydroStat says that this setup should be wired via the ZC/ZR terminals while the Taco wiring diagram says that this setup should be wired via the TT terminals and the ZC/ZR terminals jumpered. How should this be wired for multi-zone cold start?

As a side note, I'm having an issue where Zone 2 only circulates when Zone 1 calls for heat. When Zone 1 calls for heat both zones come on. I have a feeling that the thermostats are acting up. They are brand new Honeywell RTH5160D1003 models.



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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    I think you can do it either way. I think when you wire the end switch from the relay to zr/zc on the aquastat, it has something to do with using thermal targeting and the economy feature. If you just wire the end switch to T-T on the aquastat you need to turn off the economy feature. I'd have to look up the instructions when I get back to the office.

    There was an error rendering this rich post.

  • Richtdow
    Richtdow Member Posts: 22
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    Thank you. Currently I've got it wired from the end switch to T-T on the aquastat with the economy feature turned off. I'll be on the lookout for more information after you look at the instructions.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
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    🤣

    Edward Young Retired

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

  • ZBoiler
    ZBoiler Member Posts: 11
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    I have very similar question.
    Just replaced old AquaStat Honeywell control with Hydrostat 3250 Plus. The old control didn't have ZC-ZR in addition to T-T terminals. A technician while replacing old control didn't bother, I think, with the fact that I have Uponor Three-Zone relay with 3 circulators. He reconnected X-X wires from Uponor to T-T of Hydrostat. However, it appears that ZC-ZR are 120V terminals vs. 20-30V X-X wires from Upnor relay.
    My boiler is Weil-McClain WGO-4. "Is it cold start boiler?" is my second question.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited November 2019
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    It's 'cold start' if you are not maintaining temperature for domestic hot water.
    You're usually fine with T-T on X-X, unless your boiler has an internal coil for making domestic hot water, and even then you might be ok too.
    Do you actually have a problem?

    There was an error rendering this rich post.

    ZBoiler
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
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    I am wondering if the circulator that comes on for zone 2 when zone 1 thermostat calls.. is the circulator connected to the Zone Control or the Hydrostat?

    Edward Young Retired

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

    ZBoiler
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
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    I have very similar question.
    Just replaced old AquaStat Honeywell control with Hydrostat 3250 Plus. The old control didn't have ZC-ZR in addition to T-T terminals. A technician while replacing old control didn't bother, I think, with the fact that I have Uponor Three-Zone relay with 3 circulators. He reconnected X-X wires from Uponor to T-T of Hydrostat. However, it appears that ZC-ZR are 120V terminals vs. 20-30V X-X wires from Upnor relay.
    My boiler is Weil-McClain WGO-4. "Is it cold start boiler?" is my second question.

    @ZorianPinsky WGO is a cold start. If you had a WTGO it would maintain temperature for a domestic hot water tankless coil. "Cold start"as opposed to "maintain temperature".

    You don't need to concern yourself with this. informational :wink: Originally the ZR is 120V that provide 120V for burner thru the limit switch on the Hydrostat or Aquastat. ZC provides 120V power to the zone control. It is used to prevent the boiler temperature from dropping to low for DHW when a zone circulator operates for heat.

    Edward Young Retired

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

    ZBoiler
  • ZBoiler
    ZBoiler Member Posts: 11
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    Thank you, all.

    I don't have a problem, except that I am trying to understand if I am now utilizing all the features of 3250 relay as old Honeywell didn't have them.

    To begin with, all the circulators (3 of them) are controlled by a zone relay - new Uponor Three-Zone. One of the zones is radiant heat. My house hot water is produced by a separate water heater.

    Here are my questions:

    1) Am I really utilizing 3250's Economy Feature if my zone relay is connected via its X-X terminals to T-T of 3250 relay? Would setting of it, see page 7, to 3 would be meaningful with the existing connection arrangement? Currently, it is set to 1 (factory setting).

    2) From 3250 installation instructions, page 6, Step 3B, it isn't clear what is the functional difference of the relay would be if Multi-Zone panel is connected to ZC-ZR vs. T-T. What is it?

    3) What limit switch on Hydrostat are you referring to? What is DHW?

    Thank you.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
    edited November 2019
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    Since you do not have an indirect Domestic Hot Water (DHW) tank. do not use the ZR. You should look like diagram 8 on page 6. Set the economy setting to the number of zones you have and then see what happens. If you don't get enough heat turn the number to 1 less. If you get enough heat you can try 1 higher. That simple!
    When I say limit switch... I mean the part of the Hydrostat control that shuts off the boiler when it reaches the limit setting. Back in the day all the parts of the Hydrostat control were separate components The limit part was called a limit switch. It automatically opened the circuit when the set point temperature was reached to stop the burner. It automatically closed when the water cooled below the set-point less the differential to allow the burner to fire

    The "Switch" is not something you turn off or on. It is the temperature you set for "Hi Lim" or "HL"

    Edward Young Retired

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

  • ZBoiler
    ZBoiler Member Posts: 11
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    So, what happens to the system if in the Economy Feature's number of zones is set to 1, 2 and so on? What is the meaning of setting to a number higher than 1 if only X-X wire comes from the zone relay? How can 3250 detect the difference, then?
    Rickoo
  • HVACNUT
    HVACNUT Member Posts: 5,876
    edited December 2019
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    The sensor in the 3250 Plus doesn't care how many zones. It takes boiler temperature readings during a heat cycle and widens or narrows the differential based on that temperature.

    The Economy settings are approximate to the number of corresponding space heating zones (less an indirect). In a perfect world, great. Sometimes it needs to adjusted and that should be explained to the end user so they can adjust it if needed.

    If both your space heat zones, and indirect zone are wired into a multiple zone board, then the priority switches in both the relay board and the 3250 Plus are switched on.
    The Priority indirect circuit will have 2 hot wires on the circulator connection. 1 for the indirect circulator, the other wire (I use a Red wire for ZR, and Blue for ZC) connects to ZR in the 3250 Plus.

    By doing that, when the indirect gets a demand, then the indirect's circulator is energized, as well as ZR. When that happens, the circuit for TT internally opens and switches from Economy to Full Throttle.
    STEVEusaPA