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Rooftop Dedicated Outdoor
Air System Installation Manual
Due to our policy of continuous product innovation, some specifications may change without notification.
©LG Electronics U.S.A., Inc., Englewood Cliffs, NJ. All rights reserved. “LG” is a registered trademark of LG Corp.
CONTROLLER
Temperature Control
Temperature control sequences determine when the unit is in fan-only, heating, or cooling modes. The following control sequences are avail-
able:
Supply Temperature Control: The heating and cooling devices modulate to maintain the supply air temperature set-point.
Space or Return Temperature Reset: The supply temperature set-point is calculated based on the active set-point (see below) and the
current space or return temperature. The calculated set-point is scaled between the supply temperature minimum and maximum set-points
determined by the current mode of operation.
Active Set-point: The heating and cooling set-points are determined by the temperature set-point and deadband. The deadband is divided by
two (2) and added to and subtracted from the set-point to determine the cooling and heating set-points.
•
Dual Set-point Mode: When a deadband value is greater than zero, the unit is placed into dual set-point mode.
• Cooling: If the space or return temperature is above the cooling set-point, the cooling set-point is active.
• Heating: If the space or return temperature is below the heating set-point, the heating set-point is active.
• Transitioning between set-points: if the space or return temperature is between the heating and cooling set-point, the last active set-point is
used.
• Start between set-points: if the unit starts while in between set-points, the heating set-point is active.
•
Single Set-point Mode: If a deadband of zero is entered, the unit is in single set-point mode and controls directly to the user-entered tem
-
perature set-point.
Outside Reset: The heating and cooling devices modulate to maintain the supply air temperature set-point as determined by the outside reset
calculation.
• Outside Reset Calculation: The supply temperature set-point is scaled between the supply temperature minimum and maximum set-
points as the outside air temperature changes between the outside reset minimum and maximum set-points.
Heat / Cool Mode Switch Delay: This delay is used in transitioning between heating and cooling modes. The delay timer starts counting when
the unit is no longer heating, cooling, or economizing.
1. Enable Heating: The unit enables heating when the following occurs:
• All cooling devices are off; and
• Economizer is at zero; and
• The heat cool mode switch timer has expired; and
• Heating is not locked out; and
• There is a demand for heating.
2. Enable Cooling: The unit enables cooling when the following occurs:
• All heating devices are off; and
• The heat cool mode switch timer has expired; and
• Cooling is not locked out; and
• There is a demand for cooling.
Fall Back: During a sensor failure the temperature control mode reverts to the previous available option based on the following order:
• Supply temperature control
• Outside air reset
• Space/return reset
• If both space and return temperature sensors are present, the remaining sensor is used during a failure.
Sequences of Operation
