Lennox ComfortSense 3000 Series Commercial Programmable Thermostat

Introduction

The Lennox ComfortSense® 3000 Series Commercial Programmable Thermostat, Model COSTAT05FF1L (11Y05), is a 5/2 day programmable electronic thermostat with 2-heat and 2-cool capabilities. It features a programmable filter change reminder, an equipment maintenance reminder, and a system check indicator. This thermostat is suitable for 2-stage heat / 2-stage cool applications using a gas or electric auxiliary heat source and can also be used with an economizer.

WARNING: Improper installation, adjustment, alteration, service, or maintenance can cause property damage, personal injury, or loss of life. Installation and service must be performed by a qualified installer, service agency, or the gas supplier.

General Information

These instructions are intended as a general guide and do not supersede local codes. Consult authorities having jurisdiction before installation. Check equipment for shipping damage. If any damage is found, contact the last carrier immediately.

The remote indoor sensor, when connected and configured, will act as a room temperature sensor instead of the internal temperature sensor. A dip switch is used to select either the built-in or external remote indoor temperature sensor for temperature control.

Initial Thermostat Power-up

When power is initially applied, the thermostat display will appear as shown in Figure 1. The default temperature set point is 70°F. If the equipment is powered and a heat demand is present, the system will begin operating. 'UC' indicates unoccupied, and 'OC' indicates occupied.

Figure 1. Initial Power-Up Display: Shows the day of the week, time, program status (A, B, C, D, HOLD), fan status (ON, AUTO), system status (COOL, OFF, HEAT), room temperature, and setpoint temperature.

NOTE: Temperature scale defaults to Fahrenheit but can be reset to Celsius.

Buttons, Backlight, Timers & Settings

Buttons are located behind a small door on the right-hand side of the thermostat (see Figure 2).

Figure 2. Thermostat Buttons: Illustrates the thermostat's buttons including Heat, Cool, Prog, Day/Time, Fan, Hold, Settings, and Enter. It also shows the display with Room temperature, System status, and Occupancy status (UC).

A pale blue display backlight illuminates for 30 seconds each time any button is pressed. Changes made within 15 seconds of a field flashing or a setpoint display will be saved; otherwise, the HOME screen will return.

DAY/TIME - Setting the Day and Time

Press the DAY/TIME button to set the current hour, minute, and day of the week.

1. Set the hour using the up/down arrows and press DAY/TIME.
2. Set the minutes using the up/down arrows and press DAY/TIME.
3. Set the day of the week using the up/down arrows (abbreviated MO, TU, WE, TH, FR, SA, SU) and press DAY/TIME.

The HOME screen will reappear, confirming the day and time setting.

HEAT - Using the Heat Mode

Use the HEAT button to enable or disable heat mode. When enabled, 'HEAT' is indicated in the SYSTEM box (see Figure 3).

Figure 3. Turn Heat ON/OFF: Shows the thermostat display with 'HEAT' indicated in the SYSTEM box.

When heat mode is disabled, 'OFF' is indicated in the SYSTEM box (see Figure 4).

Figure 4. Heat Mode Disabled: Shows the thermostat display with 'OFF' indicated in the SYSTEM box.

Heating Demand

In heat mode, when the room temperature is lower than the setpoint, the thermostat detects a heating demand and activates the heating equipment. Heating operation is indicated by a flame icon. The flame icon disappears when the temperature rises above the setpoint.

Timers governing heating restart include:

• Minimum furnace off timer (1.5 minutes for HG).
• Minimum cycle timer (six minutes).

COOL - Using the Cool Mode

Use the COOL button to enable or disable cool mode. When enabled, 'COOL' is indicated in the SYSTEM box (see Figure 5).

Figure 5. Turn Cool ON/OFF: Shows the thermostat display with 'COOL' indicated in the SYSTEM box.

Pressing the COOL button again disables cool mode, indicated by 'OFF' in the SYSTEM box (see Figure 6).

Figure 6. Cool Mode Disabled: Shows the thermostat display with 'OFF' indicated in the SYSTEM box.

Cooling Demand

In cool mode, if the room temperature is higher than the setpoint, the thermostat detects a cooling demand and activates the cooling equipment. Cooling operation is indicated by flashing 'snowflake' icons in the SYSTEM box (see Figure 7). The icons disappear when the temperature drops below the setpoint.

Figure 7. Cooling Demand: Shows the thermostat display with flashing 'snowflake' icons and 'HI' indicating a large cooling demand.

NOTE: If no buttons are pressed during a cooling demand, the equipment must operate for at least four minutes. After a demand is satisfied, cooling operation is locked out for five minutes. If another demand occurs during this interval, 'COOL' and snowflakes will flash, but the equipment will not operate until the 5-minute delay has elapsed.

HOLD - Using Temperature Hold Modes

When 'HOLD' is displayed on the HOME screen, the thermostat is in a temperature hold condition, ignoring program data and functioning like a non-programmable thermostat.

Adjusting Temperature Setpoint in Hold Mode

Use the up or down arrow buttons to adjust the setpoint. Each press adjusts the setpoint by 1 degree.

Figure 8. Hold Temperature Mode: Shows the thermostat display with 'HOLD' indicated.

Permanent Hold Mode

From the HOME screen, press the HOLD button to set a permanent hold. Use the up/down arrow buttons to adjust the hold set point. Press HOLD again to return to the program. Occupancy status remains unchanged.

Temporary (2-Hour) Hold

From the HOME screen, press the up or down arrow buttons until the desired set point is displayed. 'HOLD' flashes (see Figure 9). This overrides the program for 2 hours from the last button press.

Figure 9. Temporary Hold Temperature Mode: Shows the thermostat display with flashing 'HOLD' indicating a temporary hold.

To change occupancy status in temporary hold mode, press ENTER while 'HOLD' is flashing. Occupancy can be set to OC (occupied) or UC (unoccupied) by pressing ENTER.

Pressing HOLD once in Temporary Hold switches to Permanent Hold ('HOLD' displays solid). Pressing HOLD again returns to the program ('PROG' displays, 'HOLD' not displayed).

PROG - Thermostat Programming

The thermostat can be programmed for heating or cooling events for five consecutive days, with a different set of four events for the remaining two days. Both consecutive days and events/temperatures are user-set.

To Change Consecutive Days

Press and hold the PROG button for three seconds. The current 5-day period is displayed. Use the up or down arrow buttons to change the 5-day span (e.g., Saturday through Wednesday).

Figure 10. Change Consecutive days: Shows a display for selecting consecutive days.

To Set Program Events and Temperatures

Figure 11 provides an example of setting programs for a workweek and weekend. Programs A and C reflect occupied temperatures, B reflects unoccupied, and D reflects a cooler sleeping temperature.

Figure 11. 5/2 Day Program Example: Illustrates 5-day and 2-day program bar graphs showing different temperature settings for various times and occupancy states.

NOTE: Pressing ENTER during programming steps saves and exits to the HOME screen.

To program events and temperatures:

1. Press HEAT or COOL button.
2. Press and release PROG. The display shows the current hour, period (A), and consecutive days. The hour flashes.
3. Use up/down arrows to select the desired hour; press PROG.
4. Use up/down arrows to select the desired minute; press PROG.
5. Use up/down arrows to select occupancy status (UC or OC); press PROG.
6. Use up/down arrows to select the desired temperature set point; press PROG.
7. Repeat steps 3-6 for periods B, C, and D.
8. Repeat steps 1-7 for the 2-day program.

NOTE: The thermostat does not automatically switch between heating and cooling. Operator involvement is required. At season changes or for abnormal temperature swings, manually select the appropriate Heat or Cool program.

FAN - Controlling the Fan Operation

Use the FAN button to select continuous fan mode or auto fan mode.

Pressing the FAN button toggles between modes. A fan icon in the FAN box indicates the fan is running.

Figure 12. Using Fan ON: Shows the thermostat display with 'FAN ON' indicated.

In auto fan mode (see Figure 13), the fan runs only when heating or cooling equipment is operating.

Figure 13. Using Fan AUTO: Shows the thermostat display with 'FAN AUTO' indicated.

SETTINGS - Filter/Maintenance Reminders

The thermostat can remind you when the filter needs changing or when routine maintenance is required. These reminders are optional and must be activated.

Press the SETTINGS button (see Figure 14) once or twice for the desired reminder.

Figure 14. Reminder Settings Display: Shows the thermostat display with 'OFF' for MAINT and FILTER reminders.

The default setting is OFF. Use the up or down arrow buttons to select desired reminder intervals (see Table 1).

Table 1. Filter and Maintenance Reminders:

NOTE: The HOME screen reappears after 15 seconds, or press ENTER to store changes. After the programmed interval, a reminder will be displayed (see Figure 15).

Figure 15. Reminders: Shows the thermostat display with a reminder indicator.

After filter change or maintenance, press SETTINGS for four seconds to reset the reminder timer.

Internal/Remote Sensor

If an optional Remote Indoor Sensor (10K) (47W37) is connected, it serves as the room temperature sensor. Dip switch #4 selects between the built-in or external sensor.

Occupied and Unoccupied Modes

During permanent hold mode, occupancy output follows the program. During two-hour hold, the user can change occupancy status (OC or UC) by pressing the ENTER button. The occupancy relay is turned on when the user selects occupancy status during programming. The default state is off.

Table 2. Thermostat Outputs (Occupancy): Details thermostat outputs for Cooling and Heating Demands with Occupancy, showing stages of cooling/heating and continuous/auto modes.

Service Indicator

When abnormal equipment operation is detected, the 'SERVICE' indicator will flash (see Figure 16). This indicates the equipment requires service from a qualified technician.

Figure 16. Service Indicator Flashing: Shows the thermostat display with the 'SERVICE' indicator flashing.

Thermostat RESET

In case of abnormal conditions, the thermostat may need to be reset to its default condition. This deletes all programming and settings and should only be used when the thermostat fails to function as designed, or due to power surges or outages.

Figure 17. Reset Button: Illustrates the location of the recessed RESET button.

CAUTION: Pressing the RESET button reverts all settings to defaults (see Table 3). The RESET button is unlabeled and recessed, located behind the door, to the right of the SETTINGS button. Use a paper clip or small pencil to press it.

Removing/Installing Thermostat

The thermostat hinges on tabs at the top of the sub-base. Pivot the bottom outward to release snaps and lift up. To replace, align the top tabs, then pivot the bottom until it snaps into place.

Default Thermostat Settings

Table 3. Default Thermostat Settings:

Technical Specifications

• Thermostat Type: Electronic programmable thermostat for non-heat pump, 2-stage heat / 2-stage cool.
• Power Supply Range: 18VAC - 30VAC (24VAC nominal), 50Hz¹ or 60Hz.
• CAUTION: 24VAC is present on terminals. Use caution when removing the thermostat to avoid touching terminals. Use non-conductive tools for dip switches to avoid contact with the circuit board.
• Temperature Display: Fahrenheit or Celsius selectable; Range: 35°F (2°C) to 99°F (37°C); Resolution: 1°F (1°C); Accuracy: +/-1°F.

Setting Temperature Scale

Press Settings three times. Use up/down arrows to toggle between Fahrenheit and Celsius. Press Settings to exit.

Selecting Internal or Remote Sensor

Use dip switch #4 to select between the internal or remote temperature sensor. Default is internal sensor (OFF).

Figure 18. Internal/Remote Sensor Settings: Shows the internal layout with dip switches and the I/R (internal/remote) switch.

Temperature Measurement Range

• Measurement Scale: Fahrenheit
• Measurement Range: 35°F to 99°F
• Measurement Resolution: 0.125°F
• Measurement Accuracy: +/-1°F
• Field Offset: via DIP switches to +/-3°F
• Sampling Method: Temperature measurements sampled every two seconds. Displayed temperature is the average of the last four measurements.

Temperature Set Point Range

• Setting range: 50°F (10°C) to 90°F (32°C)
• Setting resolution: 1°F (1°C)

Smooth Setback Recovery (via DIP switch #6)

Smooth Setback Recovery (SSR) affects how the thermostat responds to program events. If disabled, the thermostat reacts at the event time. If enabled, it reacts before the event to reach the desired temperature at the event time.

Fan Control

AUTO or ON modes.

I/O Relays

All thermostat relays are latching type to minimize power consumption.

Table 4. Terminal Designations

Equipment Protection Timers

• Minimum Compressor OFF time: 5 minutes
• Minimum Compressor ON time: 4 minutes
• Minimum Electric Heat ON time: 3 minutes
• Minimum Furnace ON time: 3 minutes
• Minimum Furnace OFF time: 1-1/2 minutes

Minimum cycle time (furnace): 6 minutes.

Minimum elapsed time between compressor activations: 6 minutes.

NOTE: Protection timers (except compressor OFF) can be overridden using UP, DOWN, HEAT, or COOL buttons.

Equipment Protection Override

Minimum compressor OFF timer and minimum equipment cycle timer can be overridden by pressing and holding HEAT or COOL for four seconds.

Filter Reminder

Settings: Off, 1, 3, 6, or 12 months (of fan run time). A FILTER indicator is displayed when time has elapsed.

Maintenance Reminder

Settings: Off, 6, or 12 months (of chronological time). A 'MAINT' indicator is displayed when time has elapsed.