LG AR-DR11-08A Installation And Operation Manual page 69

Compressor Staging
Compressors are staged to maintain the active temperature set-point.
Modulating Compressor: The modulating compressor is used to trim capacity between stages of fixed compressors.
Fixed Compressor: Fixed compressors are staged on when more capacity is needed than the modulating compressor is capable of providing,
and staged off when the modulating compressor is at its minimum speed.
Lead / Lag Sequencing: Compressors are staged based on the lead/lag mode selected:
• Always Lead: Compressors always stage based on the order selected for lead staging.
• Always Lag: Compressors always stage based on the order selected for lag staging.
• With Dehumidification: Compressors stage based on the lead staging order when not dehumidifying. When dehumidification is active, the
compressors stage based on the lag staging order.
• Weekly: If weekly is chosen, the lead lag order switches at midnight of the user-selected switching day.
Compressor Failure: If a compressor becomes unavailable due to an alarm, that compressor will be replaced by the next available compres-
sor specified in the sequence.
Chilled Water Coil
If a chilled water coil is installed, the chilled water valve modulates to maintain the active temperature set-point when the unit is in cooling
mode. The chilled water valve can optionally be held open to maintain flow when the unit is off.
Hot Water Coil
If a hot water coil is installed, the hot water valve modulates to maintain the active temperature set-point when the unit is in heating mode.
Case Heat
Case heat is available to keep the unit casing at a specific temperature using the hot water coil.
1. Availability: The following must be true to enable the case heat function:
• Unit is in off / standby mode; and
• The minimum of the cooling coil leaving air temperature or the mixed air temp is less than the case heat set-point.
2. Hot Water Valve Modulation: When case heat is enabled, the hot water valve modulates to maintain the case heat set-point while the unit
is in standby.
Hot Gas Reheat
The hot gas reheat coil heats air to maintain supply air temperature by modulating a reheat valve when the unit is in dehumidification mode,
or when single zone, variable air volume cooling mode with reset is active.
Purge: When hot gas reheat purge occurs the hot gas reheat valve opens to 100% and remains open for the duration of the purge delay. This
function only occurs when the unit controller deems it necessary.
Due to our policy of continuous product innovation, some specifications may change without notification.
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CONTROLLER
Sequences of Operation
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