Analysis of the Control Circuit for Panasonic CU-5CHV11 Heat Pump Type Air Conditioner
This air conditioner is a split cabinet type with both cooling and heating functions, consisting of two main parts: the indoor unit and the outdoor unit. These units are connected via TM wiring board terminals ①, ⑤, ③, and ④, using a three-phase five-wire AC power supply entering the house, which is directly connected to the outdoor unit's TM wiring board in a three-phase four-wire configuration. Another grounding protection wire is connected to the metal casings of both the indoor and outdoor units. On the left side, there is the primary circuit for the H auxiliary electric heater and the compressor motor, supplied by a 380V power source, while the remaining secondary circuits are powered by a 220V power source. The 220V mains electricity also passes through fuses F1 and F2 into the CH crankcase heater, with a series connection of the normally closed contact of the 52C compressor AC contactor, ensuring that the crankcase heater preheats before the compressor starts, guaranteeing normal operation of the compressor.
At the same time, the 220V mains electricity passes through the coil of the 52R1 power relay, forming a loop via the normally closed contact of the 49C compressor thermostat, causing the 52R1 power relay to actuate and close, preparing for startup. The neutral line N of the 220V mains is connected to terminal ① of the TM wiring board, while the live line R passes through the normally closed contact of the 51C compressor thermal relay, the normally closed contact of the 63H1 compressor high-pressure relay, and the already closed contact of the 52R1 power relay to reach terminal ② of the TM wiring board, thereby providing a 220V AC working power supply to the following branch circuits.
(1) Cooling: When set to cooling mode, the operating switch connects pins ① and ⑧, as well as pins ① and ④, ensuring operation in ventilation mode. At this point, the RY1 relay of the 23 thermostat has automatically switched to the C-2 position for cooling, passing through the already actuated C, N normally closed contacts and the ①～④ contacts of the RY0 relay of the 23D defrost thermostat, forming a loop with the A-13 winding of the 52C compressor AC contactor, causing FM01, FM02, and CM to be energized and run, completing the cooling process.
(2) Heating: When set to heating mode, pin 1 of the operating switch connects to pin 6, and simultaneously pin 1 connects to pin 4, ensuring operation in ventilation mode. At this point, the primary of the T1 transformer in the thermostat forms a loop, allowing the thermostat to work, detecting the indoor temperature via the Th1 thermistor at the indoor unit's return air inlet, determining the position of the RY1 relay contacts. For heating, C-H is connected, and the VR1 potentiometer is adjusted for constant temperature setting. Pin 6 of CS forms a loop with the coil of the V1 four-way electromagnetic valve and the primary of the transformer in the 23D defrost thermostat after a self-holding time of 20 seconds via 52R5, making the 23D work. Simultaneously, the coil of the 20Sv four-way electromagnetic valve connects to the 1, 4 contacts of the relay in the 23D, making the 205V1 work, reversing the flow of refrigerant, turning the evaporator into a condenser to achieve heating.
(3) Ventilation: When set to ventilation mode, pins 1 and 4 are connected, passing through the normally closed 1, 2 contacts of the 62A delay timer relay, then through the normally closed contacts of the 52R5 intermediate relay and the COS2 conversion switch to form a loop with FM1, the indoor centrifugal fan. Switching FM can change the number of turns in the running winding, obtaining low, medium, and high wind speeds. Adjusting the position of the COS2 conversion switch allows FM1 to operate in medium or high wind speed modes. SM is the motor for the air outlet guide vanes of the indoor unit, and its position can be adjusted by switching the on and off of the COS1 conversion switch. At this time, the green light GL illuminates, indicating that the fan is working.
(4) Stop: When set to stop mode, pins 1 and 2 are connected, forming a loop through the coil of the 52R2 intermediate relay and the fuse of the H auxiliary heater TF, causing the 52R2 intermediate relay to actuate and close, maintaining itself via the closure of its own 5～9 contacts, and preparing for operations such as cooling, heating, and ventilation.
Beijing Panasonic Air Conditioning Repair Center
August 10, 2011