MotorMaster® I Head Pressure Controller for Split Systems (15 & 20 Tons)

FEATURES

Motormaster ® I solid-state head pressure control regulates out- door (condenser) fan speed during Cooling mode operation. A temperature sensor, mounted on a return bend of the outdoor (condenser) coil, controls the speed of approved outdoor (condenser) fan motors in order to maintain a constant head pressure in the outdoor (condenser) coil. When properly installed, the control will maintain the appropriate head pressure at low ambient temperatures down to –20°F (–28°C).

On all size 16/180/181 and 25/240/241 units, the single Motor- master I control is connected to two outdoor (condenser) fan motors – OFM1 and OFM3. The additional fan motors — OFM2 (all units) and OFM4 (size 25/240/241 only) — are staged off at mild ambient temperatures (below 40°F (6°C) by low ambient temperature switch LAS through low ambient relay LAR.

For Heat Pump ONLY, Speed Control Bypass (SCB) relay is energized during the Heating mode. The SCB relay bypasses the Motormaster controller output to force all outdoor (condenser) fan motors to run at full speed during Heating mode.

On 575V units, the 575V motors installed in positions OFM1 and OFM3 are replaced with 460V fan motors, powered through a stepdown (575V to 460V) transformer and controlled through a 460V Motormaster ® controller. Wind baffles are required to prevent wind cross currents from causing abnormally low condensing temperatures. Wind baffles must be field fabricated and installed using the provided dimensions.

INCLUDES