Rev.01 03-27-17
Page 12 of 67
Compu-Aire
When the Master goes offline, all standby systems become active to as standalone mode. This
reduces the chance of the controlled space temperature and humidity trails off setpoints. When
an active master or slave units goes into alarm, next standby system or all standby systems should
become active while the system in alarm is turned off. Network alarm events are programmable
via the technician menu. Communication between systems is maintained by a synced heartbeat.
The units can be set to cycle to achieve equal run time on each unit. At the end of each cycle, the
role of each unit switches to its counterpart, meaning the Master becomes the Slave and the
Slave becomes the Master during the next cycle. During each cycle, the units operate according
to the above lead/lag logic.
3.4
Air Cooled DX with Chilled Water Plus
Summary of Equipment
The primary system shall be Chilled Water Cooling. Direct Expansion Cooling shall be setup as a
back up to the Chilled Water system. Both systems are designed to work independent of each
other.
The Chilled Water System comes standard with a three (3) way water modulating valve, coil, and
an optional “
no water flow switch
”
. The DX system is equipped with a DX coil, compressor(s), and
outdoor air cooled condenser. Optional heaters and humidifiers are also available if needed.
A unique feature of Air Cooled/Chilled Water Plus units is that the chilled water coil is located at
the side of the direct expansion coil. The auxiliary chilled water coil is custom sized so that it
provides identical cooling capacity obtained during the refrigeration cycle with the compressor
operating.
Cooling-Chilled Water
Chilled Water cooling is the primary cooling system for C+ units. For optimum performance, the
controller is programmed to call chilled water cooling for the first 300 seconds regardless of the
chilled water temperature.
The C+ unit can switch over from one cooling mode to another based on sensing Chilled Water
flow or Chilled Water temperature. The standard practice is to sense the Chilled Water flow for
switching.
If
“
No Water flow
”
switch is selected, the unit senses the flow of chilled water by using a pressure
differential switch and switches over to DX cooling based on loss of water flow. When no water
flow switch is selected for switch over, the unit will only work on either DX or C.W. cooling mode.
If chilled water supply temperature is selected for switch over, than the unit shall continue with
chilled water cooling if the chilled water supply temperature is below the required temperature
set point and switch over to the DX cooling.
