Stulz CeilAir CW - Condensate Pump; Firestat; Smoke Detector; Water Detector

17OCH0006F08/13/2024
CEILAIR
®
CW & DX IOM
1.7 FREECOOLING OPERATION
1.6.5 Condensate Pump
An optional, factory-installed condensate pump may be provided. The pump automatically eliminates
condensate and humidifier flush water (if applicable) from the drain pan. Should an overflow occur in an E²
based system, the pump overflow safety switch triggers a contact signal to the controller that indicates the
alarm condition, and the controller automatically shuts down the compressor and optional humidifier until the
condition is corrected. The blower(s) will continue to operate. In an ATech system, the pump safety switch is
wired directly to the OHS remote stop/start terminals to cut power to the system.
1.6.6 Smoke Detector
A smoke detector may be mounted in the return airstream to sense the presence of smoke and, when smoke
is detected, shut down the air conditioner, either via the E² controller or in ATech systems via connection to
the OHS remote stop/start terminals.
1.6.7 Firestat
A fire detector (firestat) may be mounted in the return airstream to sense high return air temperature
indicative of a fire. The system shuts down, either via the E² controller or, in an ATech system, via connection
to the OHS remote stop/start terminals. Following activation, the firestat must be manually reset using the
reset button on the firestat before restarting the unit.
1.6.8 Water Detector
As an option, STULZ offers spot type or strip/cable type water detectors. In units equipped with an E²
controller, when water is detected the controller turns off cooling and humidification, while the blower(s)
continue to operate. The unit will automatically restart when the condition is corrected. In units equipped with
an ATech thermostat, the water detector is wired to the OHS remote stop/start terminals and power to the
system is cut when water is detected.
1.7 Free-Cooling Operation
The free-cooling (FC) configuration illustrated in Figure 4 is available to minimize the use of compressor
operation during low ambient conditions for system energy savings. An FC system utilizes a remote drycooler
to provide water/glycol coolant to a free-cooling coil positioned within a DX refrigerant system. If outdoor
air temperatures permit free-cooling operation (adjustable user setpoint), the free-cooling mode is enabled
to take advantage of the low ambient conditions to provide cooling with partial use or without the use of
the system compressor(s). Free-cooling provides an excellent opportunity for reduced operational cost
by reducing the compressor operating hours. The free-cooling sequence is enabled if the entering fluid
temperature is below the user adjustable free-cooling-enabled setpoint and the return air temperature rises
to the free-cooling setpoint plus dead band. The drycooler pump activates and the three-way control valve
directs chilled water/glycol coolant to the FC coil. The outdoor fluid cooler is controlled by first switching
the leaving fluid control setpoint from typical DX heat rejection to free-cooling control (adjustable setpoint,
ambient air) and by controlling the leaving fluid to its user-adjustable setpoint. The free-cooling control valve
opens proportionally to the demand for cooling based on the return air temperature’s deviation from setpoint.
If the return air temperature continues to rise, the free-cooling valve position eventually reaches 100% open,
maximizing the flow of coolant through the free-cooling coil. Continued operation in this position indicates the
A/C unit is unable to lower the air temperature to the desired setpoint in the free-cooling mode.