OM 135
PFS 155C - 315C
21
Guardistor Board
The Guardistor board monitors the motor winding temperature through the embedded Guardistor
sensors. If the motor temperature rises to an unsafe level, the board will signal the M280 controller
and the chiller will be shut down.
Figure 7, Guardistor board
Power Transformers
Transformers T2,T3 and T4 provide operating power to the MicroTech controller and it’s associated
components. T2 is a conventional ferrite core transformer that converts 120VAC from the control
transformer into 24VAC. T3 and T4 are transformers that convert 24VAC from T2 into a center-tapped
18VAC.
Keypad / Display
The Keypad/Display is the primary operator interface to the unit. All operating conditions, system
alarms and setpoints can be monitored from this display and all adjustable setpoints can be modified
from this keyboard if the operator has entered a valid operator password.
