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Combining Controls

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KnightElectric
KnightElectric Member Posts: 4
in Thermostats and Controls
Sorry i have not had time to read your archives. Can I combine a Terkmar 361 control with a Taco SR504 4 zone relay. The system in question is a 3 zone radiant with circulator pumps and 1 domestic hot water zone with a circulator pump. No zone valves. Thanks, Kurt

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  • Ironman
    Ironman Member Posts: 7,376
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    Yes, but your piping scheme must be designed for it. This is true with any system: the piping and control scheme should be designed together.
    The 361 is designed to operate a variable speed injection mixing pump based on outdoor reset. This requires piping a mixing bridge between the boiler loop and the system or zone loop.
    You should download the install manual for the 361 as well as Tekmar's essay on injection mixing and make sure that you grasp the concept and that your system is piped as shown.

    You will use the "X X" (end switch) terminals on the SR504 to signal the "mixing demand" terminals on the 361. These are simple dry contacts on the SR504 and have no voltage output of their own. The 361 is looking for 20 - 260 volts input on the mixing demand terminals. This means that you'll have to apply high or low voltage through the "X X" terminals and on to the 361 mixing demand terminals. I would take one side of the 24 volt output from the SR 504's transformer (the "R" terminal) and run it through the "X X" terminal and on to one side of the "mixing demand" terminals on the 361. The take the other side of the 24v output ("C" terminal) straight to the other side of the "mixing demand".
    Follow the wiring diagram in the 361 for the rest. It's fairly simple.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • KnightElectric
    KnightElectric Member Posts: 4
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    Ironman; Thanks for getting back to me. The plumbing scheme is correct. Have wired several systems like this in the past but the past packages came with a different Tekmar controller. Don't remember the number off hand, but all the system pumps, DHW pump and the zone circulators were all controlled by one Tekmar controller. When using the Taco relay, and there is a demand for DHW only, ( wired to zone 4 priority in the Taco relay ) will the variable speed injector pump run until the radiant manifold is satisfied by the mixing sensor ?
  • Ironman
    Ironman Member Posts: 7,376
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    Yes, because the "X X" contacts close when any zone calls. This is on the older model SR504 which has a metal cover. The new model (plastic cover) gives you two sets of "X X" terminals: one for the priority zone and the other set for non priority zone calls.
    You could wire the priority X X contacts directly to the boiler for a domestic call.
    If the boiler is a mod/con, it will have separate terminals for the indirect's aquastat or sensor as well as separate pump terminals for the domestic pump. In that case, I'd connect the domestic pump and aquastat directly to the boiler, not the SR504. In this scenario, remove the jumper between "ZC and ZR" on the 504 and connect "ZC" directly to the "system pump" terminal on the mod/con. This will cause the space heating circ's in the 504 to de-energize when there's a domestic call. CAUTION: the boiler and the 504 must be on the same circuit to do this.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • KnightElectric
    KnightElectric Member Posts: 4
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    Ironman, Thanks again for the help. The boiler is not a mod/com type and the Taco control is the new plastic cover. My last question is; Since the past Tekmar controllers had a true unoccupied mode due to the DHW circuit was controlled by the Tekmar, Would I install a separate switch on the DHW aquastst circuit to prevent the DHW zone from operating during unoccupied mode ? Kurt
  • Ironman
    Ironman Member Posts: 7,376
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    If that's what they desire, but I wouldn't use it unless it was an extended period like a vacation. The newer indirects are so well insulated that it makes no sense to me to turn them off overnight.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • KnightElectric
    KnightElectric Member Posts: 4
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    Yes I agree, but this home is a weekend home in Maine. They come up every weekend and go home on monday morning . Thanks again for all your help. Kurt

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