Troubleshooting guide
MAGNUM VERSION 8 MANUAL REVISION 3.1
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example if the target is 45.0F and Setpoint #119 is 10.0F, then the ambient temperature must be less than
35.0F to enable the economizer function to begin.
If mechanical cooling has not been enabled (no steps are Wanted On or Actual On), when the economizer
starts the Unit State will be ECONOMIZER ONLY. In this state mechanical cooling will not be started until
the economizer function has reached its maximum capacity (Economizer valve is at maximum opening, all
available fans are turned on, and the control temperature is still not in the target zone).
When the economizer logic starts, the Magnum will modulate the Analog Output to the economizer valve
to maintain the control sensor reading within the target zone. The valve will be modulated between
Setpoint #121“Eco MIN VLV%” and Setpoint #122 “Eco MAX VLV%” and will wait the time contained in
Setpoint #124 “EcoVlvAdjDly” before making each adjustment to the valve opening.
If control temperature is above the control target, Setpoints #1, and the control temperature rate of
change is greater than the value of Setpoint #27 “MAX ROC-”:
This indicates that the control temperature is too high and it is not approaching the target fast
enough, therefore the valve opening must be increased if possible. The adjustment value will be
the difference between the target (Setpoint #1) and the control sensor temperature multiplied by
Setpoint #126 “Eco MULTI” and divided by Setpoint #127 “Eco DIVIDE”. If the absolute
adjustment is greater than the value of Setpoint #123 “Eco MAX ADJ”, then it will be limited to this
value. The economizer valve opening will be increase by this value.
If control temperature is below the economizer control zone (Setpoint #1 - Setpoint #3) and the
control temperature rate of change is less than the value of Setpoint #28 “MAX ROC+”:
This indicates that the control temperature is too low and it is not approaching the target fast
enough, therefore the valve opening must be decreased if possible. The adjustment value will be
the difference between the target (Setpoint #1) and the control sensor temperature multiplied by
Setpoint #126 “Eco MULTI” and divided by Setpoint #127 “Eco DIVIDE”. If the absolute
adjustment is greater than the value of Setpoint #123 “Eco MAX ADJ”, then it will be limited to this
value. The economizer valve opening will be decrease by this value.
If control temperature is above the bottom of control zone (Setpoint #1 - Setpoint #3) but less than the
control target (Setpoint #1) no change to the economizer valve opening will be made.
Once the valve has reached its maximum opening (Setpoint #122), the Magnum will wait the time specified
in Setpoint #125 “Eco StageDly” before checking if there are any fans associated with the economizer
function. If there are the Magnum will stage the fans to maintain the control temperature with in the target
zone. If a fan VFD is present, then this will be modulated in the same manner. The delay between VFD
adjustments will be the value in Setpoint #115 “EcoVFDfanDely” if active, else Setpoint #124 will be used.
Once all fans associated with the economizer function are on, the Magnum will check if any condenser
fans can also be used. If yes, then these fans will then be staged to maintain the control temperature.
Once all the fans and/or VFD have been turned on and the control temperature is still greater than the
control zone for the time specified in Setpoint #107 “EcoDelayMech” if active (else the time in Setpoint
#125 “Eco StageDly” will be used) then mechanical cooling will be enabled.
If the ambient temperature rises above the offset in Setpoint #119 during economizer cooling mode,
then the economizer function will be terminated, its valve opening will be set to zero, and mechanical
cooling will be enabled.
If the control temperature is less than the target temperature (Setpoint #1) minus the 3 times value of
Setpoint #3, then the economizer function will be terminated, its valve opening will be set to zero, and
all fans will be turned off.