1-14
1.5.5.9 Refrigeration Compressor (C1)
Reference Drawing 91S25908
The Refrigeration Compressor is energized by applying a low from TIB channel B4 to the
optical input (-) side of SSR8. Compressor voltage is 100/120 VAC (220/240 VAC for HV
option).
1.5.5.10 Flow Valve (V1) – Actuation
Reference Drawing 91S25910
The Flow Valve is used to control system mass flow rate and is driven indirectly via pulses
from the Terminal Interface Board (TIB) channels B1 & B3, which trigger stepper motor
driver SMD-1. Pulses on channel B1 close the valve, while pulses on channel B3 open the
valve. The stepper motor driver is powered from the unregulated 24 VDC output of the
STD-PS circuit board in the STD card cage. The HOME or FULLY CLOSED position is
sensed by a low at TIB channel A1 resulting from the contact closure of limit switch SL-1.
1.5.5.11 Expansion Valve (V2) – Actuation
Reference Drawing 91S25911
The Expansion Valve is used to control saturation pressure and is driven indirectly via pulses
from the Terminal Interface Board (TIB) channels B0 & B2, which trigger stepper motor
driver SMD-2. Pulses on channel B0 will close the Expansion Valve, while pulses on
channel B2 will open the Expansion Valve.
The stepper motor driver is powered from the unregulated 24 VDC output of the STD-PS
circuit board. The HOME or FULLY CLOSED position is sensed by a low at TIB channel
A0 resulting from the contact closure of limit switch SL-2.
1.5.5.12 Reservoir Liquid Level Transducer (LL1)
Reference Drawing 91S25910
The Reservoir Liquid Level Transducer monitors reservoir water level, which is displayed on
the computer screen. A voltage corresponding to the reservoir water level is output from LL1
to the STD-CPU via TB2-9. When an empty indication occurs during RH generation an
audible alarm will sound accompanied by a warning message. An empty reservoir during
start up forces a shutdown, accompanied by both audible and visual alarms. The liquid level
board is powered from +5 VDC.
