The following control options provide a complete range of control alternatives for almost any application. If none of the following are selected, then the unit can be enabled via an external signal to the External Interlock Auto/Stop terminals in the unit control panel. (Refer to page 14 under Unit Control Features for a description of this feature.)

Programmable Night Heat Morning Warmup Control

This option provides comprehensive cooling and heating controls using the microprocessor logic of the unit control module along with a unit mounted programmable timer. With this control option the unit is capable of operating in four modes:

• Unoccupied Night Heat Mode
• Morning Warm-up Mode
• Occupied Heating Mode
• Occupied Cooling Mode

In all modes, the inlet guide vanes (if provided) are driven to the fully closed position when the fan is turned off. When the fan is turned on the inlet guide vanes modulate in response to supply air static pressure.

Two separate zone temperature sensors ship with the VAV units for field installation. One sensor is provided to sense the night heat temperature level. The other sensor is for morning warm-up/occupied heat temperature control. Both setpoints are adjustable from 40 to 90 degrees F at the unit control module. Sensors are to be field installed in the conditioned space or mechanical equipment room as required.

On non-VAV units the standard zone cooling temperature sensor is used to sense temperature. Separate set points are provided for night heat, day heat/morning warm-up and zone cooling. The morning warm-up setpoint is the same as the day heat set point. The night heat setpoint setting must be less than the day heat/morning warm-up set point setting. If not, the unit control module will control both day and night modes of heat based on the day heat/morning warm-up setpoint.

The operation of each mode is described below:

UNOCCUPIED NIGHT HEAT MODE — This mode is initiated by the programmable timer. The unit control module will respond as follows:

• An unoccupied output (a set of normally open and normally closed contacts) is energized.
• A ventilation output (a set of normally open and normally closed contacts) is de-energized. This can be used to close fresh air damper.
• The supply air fan and heat relay contact closure output (a set of normally open and normally closed contacts) are cycled on and off in response to a demand for heat based on the zone temperature setting.
• The airside economizer fresh air damper (if provided) is fully closed.
• The heat/cool mode output (a set of normally open and normally closed contacts) is energized. This can be used to put the VAV boxes in heating mode.
• Water flow through the waterside economizer (if provided) is shut off.
• The economizer and mechanical cooling functions are disabled.
• The cooling tower/condenser water pump output (a set of normally open and normally closed contacts) is de-energized.

MORNING WARM-UP MODE – This mode is initiated by the programmable timer. The fan and heat output is energized until the morning warm-up temperature setpoint is reached. All other conditions remain the same as in the unoccupied night heat mode.

When the morning warm-up temperature setpoint is reached, the unit will switch over to the occupied heating mode.

If no heat is required in the morning warm-up mode, the unit will go directly into the occupied heating mode.

OCCUPIED HEATING MODE — This mode provides a transition between morning warm-up and the occupied cool mode. In this mode, the unit will function as follows:

• The supply air fan is on continuously.
• The heat relay output is de-energized.
• The unoccupied output is de-energized.
• The ventilation output is energized.
• The airside economizer fresh air damper (if provided) is open to minimum position.
• The heat/cool mode output remains energized.
• Water flow through the waterside economizer (if provided) remains shut Off.
• The economizer and mechanical cooling functions remain disabled.
• The cooling tower/condenser water pump interlock output remains de-energized.

If the conditioned zone temperature drops 2 degrees F below the morning warm-up setpoint setting, the heat relay cycles to maintain zone temperature.

If the conditioned zone temperature rises 2 degrees F above the morning warm-up setpoint setting, the unit will switch over to the occupied cooling mode. At this point, the heating cycle will be locked out until the next night setback/morning warm-up cycle is initiated.

With the factory installed electric heat option, the controls are all prewired to the heat relay output. With a steam or hot water coil, the heating controls must be field wired to the heat relay output.