In the diagram, the same hydronic piping layout (at right of the dashed line) works with hot water source and chilled water source. Switching between the heat source and cold source is based on operating mode, and is controlled by outdoor temperature change, a manual switch or combination of both. When switching from winter mode to summer mode, the relay R6 is activated, system will supply chilled water via the 3-way valve.
No matter in which mode - winter or summer, as long as any of zone stats has demand (calling for heat or cooling), the zone valve relay R12 and/or R13 are activated as well as HC pump relay R1.
In the Winter mode, the controller calculates theoretical supply temperature to the radiant zone: Flow Set, by our pre-set heating curve and outdoor temperature S5; based on the calculation, the controller commands the 3-way mixing valve to open for getting more hot water from heat source (S1 < Flow Set) or close for allowing less hot water from heat source ( S1> Flow Set).
In the Summer mode, the controller calculates theoretical supply temperature to the radiant zone: Flow Set, by our pre-set cooling curve/constant value; based on the calculation, the controller commands the 3-way mixing valve to open for getting more cold water from cold source ( S1 > Flow Set) or close for allowing less water from cold source ( S1< Flow Set). Beside this, condensation control is necessary in radiant cooling systems. the controller has a built-in psychrometric chart algorithm. FRHd provides ambient temperature and relative humidity of the radiant zone, and the controller calculates the dew points. So the controller keeps the lowest cold water supply temperature to the radiant zone, but also ensures that this supply temperature is 4ºF above the dew points.
Heat Pump is the most versatile heating/cooling source. The winter & summer operation switchover is controlled by reversing valve that is part of the heat pump. The controller through the pre-wired dry contact relays in electrical enclosure can talk to any heat pump equipped with external dry-contact signal for switching the operating modes and calling compressor:
These concept diagrams have exactly same piping at heating/cooling load side as above.
The difference is that 3-way diverting valve (relay R6) is not used as its function has reversing valve inside heat pump. The individual 3-way mixing valve & HC pump are part of PAW K32 station supplied with the kit. Beside only radiant heating/cooling zones the fancoils can be added. These will require different supply temperatures: much higher in winter and lower in summer mode.
Current Literature
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