Chapter 1: Overview
Product Overview
Page 6
The refrigerant is used over and over again, absorbing heat from the indoor environment and discharging the
condenser heat to the outdoor environment.
The Control System (Controller Box)
The AIRSYS controller box is designed to operate a fully or partially redundant air conditioning system for
equipment shelters or enclosures. Two variations of the AIRSYS Lead Lag Controller are available: ASLLC.2 &
ASLLC.2.48.
ASLLC.2 is standard for HVAC equipped with an AC EC evaporator fan.
ASLLC.2.48 is standard for HVAC equipped with a DC EC evaporator fan.
The controller box is factory programmed with standard industry set points but can be configured on-site to meet
specific needs. Settings are retained indefinitely in the event of a power loss.
Ease of Control and Configuration
The controller box has a convenient Programmable LED Display (PLD). The PLD and button actions are explained
in more detail in Chapter 3 starting on page 48. This three-button PLD is the user interface by which an operator
can do the following:
Check current status of the HVAC system, such as sensor readings and operating mode
Change factory set points
Place the system temporarily into comfort mode
Review alarms and alarm history
Labeling on the outside of the controller box provides a convenient guide on how to access the most common
functions.
Many of these same functions can be accessed remotely via an RS485 communication interface built into the
controller.
Lead and Lag Roles
When mechanical cooling (MC) is required to maintain site temperature, only one unit is called upon to provide the
cooling. The unit that has this primary role during MC is referred to as the lead unit. The unit functioning in a
backup role during periods of MC is referred to as the lag unit. After a set period of time, the lead and lag units
switch roles. This scheduled change of roles ensures an extended and balanced operational life for each unit. The
factory default for the scheduled switch of roles is 168 hours (seven days); however, this can be adjusted using the
PLD (1 to 999 hours).
The lag unit will provide MC if the lead unit is unable to maintain site temperature on its own. This MC assistance
will occur if the heat load at the site is higher than the cooling capacity of a single WPU or if the system in the lead
role is functioning at a reduced capacity. A system in this state should be serviced as soon as possible.
During periods of free cooling (FC), both the lead and the lag units work together. This ensures longer periods of FC
which minimizes compressor run time. This design extends the life of the system and reduces energy consumption.
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