M thermal Split
Midea M thermal Split 
2.2 Hydronic box Piping
Figure 2-2.2: Hydronic box piping diagram
 
Legend
1 Water side heat exchanger 9 Water pump 
2 Water flow switch  10  Manometer 
3 Refrigerant liquid line temperature sensor  11  Safety valve
4 Refrigerant gas line temperature sensor 12  Refrigerant gas side 
5 Water outlet temperature sensor 13 Refrigerant liquid side
6 Water inlet temperature sensor  14  Water outlet
8 Expansion vessel   
Key components: 
1. Air purge valve: 
Automatically removes air from the water circuit. 
2. Safety valve: 
Prevents excessive water pressure by opening at 43.5 psi (3 bar) and discharging water from the water circuit. 
3. Expansion vessel: 
Balances water system pressure. (Expansion vessel volume: 8L.) 
4. Water flow switch: 
Detects water flow rate to protect compressor and water pump in the event of insufficient water flow. 
5. Backup electric heater: 
Provides  additional  heating  capacity  when  the  heating  capacity  of  the  heat  pump  is  insufficient  due  to  very  low 
outdoor temperature. Also protects the external water piping from freezing. 
6. Manometer: 
Provides water circuit pressure readout. 
7. Water pump: 
Circulates water in the water circuit. 
   
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14                                                                                                                                                                                                                        202004 
Midea CAC