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Constant Circulator Controls with TRVs

Long timer lurker. This forum has been fantastic. Appreciate all you help with the following question.

I am installing a new hydronic heating system that looks exactly like the Siegenthaler design in an image attached here. I am looking for guidance on how to wire the controls, specifically for the circulator.

The system is as follows;
Bosch zbr21-3 heat only boiler with an FW200 controller
3 pipe 50 gallon buffer tank
Manifold distribution to panel radiators equipped with TRVs .
Grundfos Alpha 15-58 circulator

The FW200 controller will be wired to an outdoor temperature sensor for ODR and WWSD. The boiler "system supply" temperature sensor will be located in the thermal sensor well of the buffer tank about halfway up the tank. The boiler will maintain the buffer tank at a supply temperature specified by the outdoor reset curve.

The type 22 panel radiators are all sized based on a detailed heat loss calculation and a system supply temperature of 120deg at a design day of 5deg and system delta T of 20 degrees. All radiators are equipped with TRVs

The grundfos Alpha 15-58 will circulate supply water constantly to the radiators in auto adapt proportional pressure mode.

How should this circulator be wired/controlled? It would seem like I should wire it to shutdown with the boiler at the Warm Weather Shutdown temperature. However I am unsure of how to do this with the Greenstar/FW200 configuration. Maybe I should just wire it to an on/off switch that gets turned on/off for the heating season. Any past experience wiring a constant circulator with pure TRVs or any diagrams literature is appreciated.


  • nosirra1Arrison
    nosirra1Arrison Member Posts: 57
    The Alpha has a Manual Summer Mode (section 8.6, page 15 of the manual). Shuts down pump and exercises pump every 24 hours.
  • neilc
    neilc Member Posts: 2,708
    So 1 temperature?
    same temp for floors and panels?
    I think you need to lose the trvs, and add mix valves there, with mix circs,
    known to beat dead horses