Common Fan - Coil Unit Control Systems

The two - pipe combined cooling and heating system consists of a thermostat, a fan - coil unit, and an electric valve. According to different application systems, the electric valve can be a two - way valve or a three - way valve. A two - way valve is selected when the system has no bypass; a three - way valve is used when the system has a bypass.

During normal cooling or heating, chilled water/hot water flows through the coil and returns. When cooling or heating is not required, chilled water/hot water flows back through the bypass and does not pass through the coil system. According to different control principles, the electric valve can be further divided into a two - wire valve and a three - wire valve.

Working Principle:
In the two - pipe combined cooling and heating system, chilled water circulates in the system during summer cooling, and hot water circulates in the system during winter heating. The thermostat continuously detects the room temperature and compares it with the set temperature. Based on the comparison result, it controls the opening and closing of the electric valve, thus keeping the room temperature constant.

System Wiring Requirements:
For high - voltage cables, it is recommended to use BV1.0 single - strand copper wire. For a non - controlled valve system, 5 wires are required; for a two - wire valve system, 6 wires are needed; and for a three - wire valve system, 7 wires are required.

Two - pipe Fan - coil Unit System with Electric Heating
The two - pipe system with electric heating consists of a thermostat, a fan - coil unit, an electric valve, an electric heater, and a contactor, etc.

Working Principle:
The thermostat continuously detects the room temperature and compares it with the set temperature. Based on the comparison result, it controls the opening and closing of the electric valve and the electric heater, so as to keep the room temperature constant.

System Wiring Requirements:
For high - voltage cables, it is recommended to use BV1.0 single - strand copper wire, and 7 wires are required.

Four - pipe Fan - coil Unit System
The four - pipe system consists of a thermostat, a fan - coil unit, and an electric valve. According to different application systems, the electric valve can be a two - way valve or a three - way valve. A two - way valve is selected when the system has no bypass; a three - way valve is used when the system has a bypass. During normal cooling or heating, chilled water/hot water flows back through the coil. When cooling or heating is not required, chilled water/hot water flows back through the bypass.

Working Principle:
The four - pipe system contains two independent heat - exchange devices for chilled water and hot water. When the chilled - water valve is opened, the system provides cooling; when the hot - water valve is opened, the system provides heating. The thermostat continuously detects the room temperature and compares it with the set temperature. Based on the comparison result, it controls the opening and closing of the electric valve, thus keeping the room temperature constant.

System Wiring Requirements:
For high - voltage cables, it is recommended to use BV1.0 single - strand copper wire, and 7 wires are required.

One - to - multiple Fan - coil Unit Control System
Note: The simultaneous appearance of two - pipe and four - pipe systems in the legend is only to illustrate the system wiring, not to imply that both systems will appear in the same project.

System Composition:
The one - to - multiple fan - coil unit control system is mainly applied in large - space scenarios with multiple fan - coil units. The system consists of individual thermostats, a drive module, fan - coil units, electric valves, etc.

Working Principle:
In the one - to - multiple fan - coil unit control system, individual thermostats are connected to the drive module to control multiple fan - coil units to start and stop simultaneously. The thermostat continuously detects the room temperature and compares it with the set temperature. Based on the comparison result, it controls the opening and closing of the electric valve, thus keeping the room temperature constant.

System Wiring Requirements:
For the power cable of the drive module, it is recommended to use BV2.5 single - strand copper wire. For the cable from the drive module to the fan - coil unit, it is recommended to use BV1.0 single - strand copper wire. When there is no controlled valve, 3 wires are required; for a two - pipe two - wire valve system, 4 wires are needed; in other cases, 5 wires are required.
For the connection cable between the thermostat and the drive module, it is recommended to use RVV0.5 - sized flexible wire. When there is no controlled valve, 5 wires are required; for a two - pipe two - wire valve system, 6 wires are needed; in other cases, 7 wires are required. The maximum allowable length of the cable is 10m.