Trane IntelliPak SAHL Series Installation, Operation And Maintenance Manual page 97

Unit Start Up
Units with Evaporative Condenser Sequence of Operation
Upon a power up without water in the sump, the condenser sump drain will be controlled to allow
the sump to hold water. The fill relay will be energized if there is a call for mechanical cooling and
if the outdoor air temperature is greater than 10°F on units with a sump heater installed or greater
than 40°F on units without sump heat.
Once the fill solenoid is energized, the sump will begin to fill. The minimum water level switch will
close and the fill relay will be de-energized. The sump water temperature sensor is invalid unless
the minimum water level switch is closed.
If the sump water temperature is less than the setpoint (default is 38°F), the sump heater will be
energized until the water temperature reaches the setpoint plus 5 degrees (43°F for default). The
fill solenoid will remain closed for 20 minutes or until the water temperature is greater than 35°F .
Once a water temperature of 35°F or greater is achieved, the fill solenoid is energized, the sump
will continue to fill, and a five minute timer is started.
When the timer expires, the compressor lockout will be released and mechanical cooling will be
allowed. Head pressure control will be regulated by a variable speed fan until the liquid line
pressure from either circuit reaches the upper limit, which is set on the Human Interface under the
setup menu 120°F default. The liquid line pressure is converted to a temperature for display at the
Human Interface. When the temperature exceeds the upper limit, the condenser sump pump will
be energized. When the sump pump is energized, water is pumped from the sump and sprayed
over the condenser coil. If the liquid line pressure from either circuit falls below the lower limit the
sump pump will be de-energized.
When the sump pump is energized or de-energized a change in state is observed from an auxiliary
contactor to ensure proper sump pump operation. A change in states must be observed by the
auxiliary contactor within 6 seconds of the command to change states or mechanical cooling will
be locked out on a sump pump failure causing a manual reset diagnostic to be set.
The fill solenoid will remain energized and the water level will be controlled by the mechanical float
valve. If the maximum level float ever closes, an information-only diagnostic is set and the fill
solenoid is de-energized. This is an indication that the mechanical float is not adjusted properly or
a failure of the mechanical float valve has occurred. If the maximum level input is open for two
continuous minutes, the diagnostic will be cleared and the fill solenoid will be energized.
If the sump water temperature ever drops below 35°F , the drain actuator will be controlled in order
to drain the water from the sump. If there is a call for mechanical cooling and the outdoor air temp
is greater than 10°F on units with sump heat installed or greater than 40°F on units without sump
heat, the unit will be allowed to refill the sump.
The drain control can be configured via the Human Interface, and by the drain actuator installation,
to hold or drain water on power loss; the default is set to drain. Periodic purge is a cyclic opening
of the drain to remove debris and buildup from the sump and add additional fresh water to the
sump. Periodic purge has an adjustable interval from the setup menu on the Human Interface with
a range of 1-12 hours or can be set to disabled - the default position if periodic purge is not required.
The duration of the blowdown, or the time that the drain valve is opened, is adjustable to a range
of 5 - 255 seconds, with 60 seconds being the default.
The optional conductivity controller also uses this timer to open the drain, when required, based
on water quality. During this purge, the fill solenoid will remain energized to provide fresh water
to the sump to replace water being released during the blowdown. Water treatment blowdown is
provided by shorting the designated input on the customer-supplied terminal strip. This gives the
customer more flexibility in determining water conditions via external controls. Once the input is
detected closed, the drain valve will be opened for a time equal to the Human Interface adjustable
periodic purge duration.
Once the duration timer expires, or if the minimum level switch opens, the drain valve will be closed
and the water treatment blowdown input will be ignored for 15 minutes. During this blowdown the
fill relay will remain open to provide fresh water to the sump. The adjustable duration time period
should be set so that during drain operation 1 inch of water is drained from the sump with the fill
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