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1.5.5.4 Pressure Select Solenoid Valve (SOL5)
Reference Drawing 91S25907
The Pressure Select Solenoid Valve, when activated, allows the 0-50 PSIA transducer to
measure the saturation pressure. This valve is activated by applying a low from the STD-
CPU (monitored at TIB terminal C4) to the optical input (-) side of SSR4 on the Solid State
Relay Board (SSRB). Valve actuation voltage is 24 VAC.
1.5.5.5 Heat Transfer Fluid Heater (H3)
Reference Drawing 91S25908
The Heat Transfer Fluid Heater is a 500 watt resistive heating element activated by a two
stage control process. The heat limit switch (HLS2) must be in the normally closed position,
indicating that the fluid temperature is within allowable limits (below 85 °C). Activation is
then accomplished by applying a low from TIB channel B5 to the optical input (-) side of
SSR10. Heater temperature is controlled through fixed frequency pulse width modulation.
Heater voltage is 100/120 VAC (220/240 VAC for HV option).
1.5.5.6 Presaturator Heaters (H1, H2)
Reference Drawing 91S25908
The Presaturator Heaters are resistive heating elements, activated by a two stage control
process. The heat limit switch (HLS1) must be in the normally closed position, indicating
that the presaturation temperature is within allowable limits (below 95 °C). Activation is
then accomplished by applying a low from TIB channel B6 to the optical input (-) side of
SSR9. Presaturator heater temperature is controlled through fixed frequency pulse width
modulation. Heater voltage is 100/120 VAC and wiring configuration is dependent on the
primary power supply. In standard units the heaters are wired in parallel where HV option
units have the heaters wired in series.
1.5.5.7 Expansion Valve Heaters (H4, H5)
Reference Drawing 91S25907
The Expansion Valve Heaters, when activated, are used to warm the expansion valve body,
offsetting the cooling effects due to gas expansion. The heaters are activated by applying a
low from the STD-CPU (monitored at TIB terminal C1) to the optical input (-) side of SSR1
on the Solid State Relay Board (SSRB). Heater temperature is controlled through fixed
frequency pulse width modulation. Heater voltage is 24 VAC.
1.5.5.8 Fluid Circulation Pump (FP1)
Reference Drawing 91S25907
The Fluid Circulation Pump is a magnetically coupled pump energized by applying a low
from the STD-CPU (monitored at TIB terminal C6) to the optical input (-) side of relay SSR6
on the Solid State Relay Board (SSRB). Pump voltage is 100/120 VAC (220/240 VAC for
HV option).
