Pumping is then halted by the software by deactivating the
square wave at RLY 4. When not actively pumping, the output of
RLY 4 is off, and the pump’s solenoid remains in a de-energized
state.
The tube liquid presence sensor, LLT, looks for large air gaps
within the suction tube. Air gaps in this suction tube give warning
of low tank water, and if detected, the system will shut down
with a corresponding error code.
Inside the back panel (Figure 6.19) is a drain valve and port,
labeled Presat Drain, and is used to manually drain water from
the preset if desired.
6.3.3 SATURATOR FLUID CIRCULATION SYSTEM
The Saturator Fluid Circulation System is a circulating mixture of
propylene glycol and water used to control the temperature of the
saturator. Controlling the temperature of the fluid controls the
temperature and stability of the saturator and the resulting
generated humidity. The fluid circuit consists of several significant
components, fluid pump, heater, refrigeration evaporator,
saturator, and the fluid expansion tank.
Water circulated from the fluid pump, P3, exits the top of the
pump, passes through a the refrigeration evaporator, cooling as
necessary. The fluid then passes through the saturator fluid heater,
H2, and is heated as necessary. From there, it flows through the
saturator and ultimately back to the inlet at the bottom of the
pump.
A small expansion tank is also connected to the bottom pump inlet
allowing for temperature induced variation in the overall fluid
volume.
When the system is generating, 24 VDC is sourced from the ECB’s
DC CONTROL – RLY 1 to the fluid pump P3. An LED at RLY 1
indicates when it is active and power is applied to the pump. Note
that the fluid pump has built-in circuitry to protect against dry run
conditions and may therefore take several seconds to power up to
full speed when activated.
Both the saturator fluid circulation system and chamber fluid circulation system share a common expansion tank.
The tank is located at the upper left-hand corner of the system, behind the chamber.
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