Hydraulic Connection
The diagram of the plate heat exchanger connection to the heating system is shown above. The refrigerant connection between the outdoor unit and the plate heat exchanger is done similarly to a standard air conditioning system. Depending on the capacity, insulated copper refrigeration piping with dimensions of 1/4" + 3/8" (or 1/2" or 5/8") is selected according to the outdoor unit's capacity.
Note: The plate heat exchanger must be installed with the arrow on the exchanger pointing upwards, meaning that when viewed from the front, the refrigerant connections are on the left side (gas at the top and liquid at the bottom), while the connections for the heating system are on the right side. This ensures that gaseous refrigerant entering the exchanger at the top condenses inside and exits as liquid refrigerant from the bottom through the 1/4" pipe. The upper right connection is for heated water output, and the lower right connection is for heating water input.
Circulation Pump R3 should be connected to the heat exchanger's input. It is recommended to install an appropriate filter before the exchanger to capture impurities, as plate heat exchangers have narrow channels that are prone to clogging.
Flowmeter should also be installed at the heat exchanger's input, either as a flow sensor I1 (e.g., type YF-B10), which measures water flow accurately to calculate output power and COP, or as a flow switch S1 (e.g., Regulus FP214-2), which triggers at a preset flow rate. The flow sensor is a crucial safety component, ensuring constant water flow in the heating circuit. If water flow stops (e.g., due to a pump failure) during defrosting of the outdoor unit, where refrigerant can enter the exchanger at -20°C, the heating water could freeze, causing damage to the heat exchanger and potentially leading to a complete system failure, including the outdoor unit.
3-way Cooling Valve R5 is connected to the heat exchanger's output. This valve is optional and does not need to be connected if cooling is not required (e.g., for ceiling cooling). Cooling can still be used for underfloor systems.
Electric Heater R2 is connected to the heat exchanger's output, possibly after the 3-way cooling valve R5. This heater can assist the outdoor unit during extreme frost conditions when the unit's capacity is insufficient to heat the building. It can also be used to heat domestic hot water (DHW) if the DHW tank is not equipped with a separate heating coil.
3-way DHW Heating Valve R4 is installed between the electric heater (if used) and the heating system's input. It switches between heating DHW and the building. An indirect DHW tank with a large heat exchanger is recommended, as a smaller exchanger area results in lower achievable DHW temperatures. The DHW tank should ideally include an electric coil for additional heating if the air conditioning cannot meet the required temperature.
Connecting the Plate Heat Exchanger as Preheating for an Existing Electric Heating System
Air conditioning heating can be integrated into an existing electric boiler system by connecting the plate heat exchanger and a flow sensor before the electric boiler.
The system can be wired so that no modifications are made to the original electric boiler, and the plate heat exchanger preheats the water for the boiler. The original room thermostat (if present) will remain functional. The boiler is set to a lower temperature (ideally the lowest possible), while the desired heating water temperature is set on the MiniHPC. When the room thermostat triggers a heating request, the boiler's circulation pump starts and heats the water to the set temperature (e.g., 25°C). The MiniHPC detects water flow and activates the outdoor air conditioning unit. The boiler receives preheated water, allowing only the circulation pump to run without activating the heating coils. In practice, the set temperature of 25°C is so low that the electric coils are rarely triggered. In this setup, the air conditioning cannot be used to heat DHW, which continues to be heated by the electric boiler. If the air conditioning's capacity is insufficient, the boiler's water temperature must be manually increased.
The second method involves connecting various components of the electric boiler to the MiniHPC relay outputs, allowing it to control the circulation pump, 3-way valve switching, and electric heating activation. This setup enables air conditioning to heat DHW and provide floor cooling. However, it requires internal modifications to the electric boiler, voiding its warranty. This work must be performed by a certified electrician, as the boiler operates with life-threatening voltages up to 400V!
