The FR4 module is designed to drive up to four three-speed fans in parallel from a single thermostat or room controller. Individual relays with independent contacts are provided for the Three speeds of a typical fan-coil unit. This assures independent operation of the fans for a longer life expectancy.

Additional terminals are provided to drive also heating and cooling valves on all four fan-coil units in parallel.

Benefits of FR 4

Drive of upto 4 fan-coil units from a single thermostat or room controller

Multiplexing of both fan fan speed and valve control


3 Speed fan control

Fuse connection


Power connection for next unit

Power supply connection for thermostat