1. Overview

The Lennox 17G74 CS7500 ComfortSense 7500 is a commercial programmable thermostat designed for efficient management of heating and cooling systems. It features a full-color LCD touchscreen display, offering intuitive control and monitoring capabilities. This thermostat is compliant with ASHRAE, IECC, and FDD regulations, making it suitable for various commercial applications. Key functionalities include advanced programming options, energy-saving modes, and comprehensive system monitoring.

Figure 1: Front view of the Lennox CS7500 ComfortSense 7500 Thermostat display.

2. Setup

2.1 Professional Installation

Installation of the Lennox CS7500 thermostat should be performed by a qualified HVAC technician. Incorrect installation can lead to system malfunction, property damage, or personal injury. Refer to the separate installation guide provided with the product for detailed wiring diagrams and mounting instructions.

2.2 Initial Power-Up and Configuration

Upon initial power-up, the thermostat will guide you through a setup wizard. This process typically includes:

• Date and Time Setting: Configure the current date and time.
• System Type Selection: Specify your HVAC system type (e.g., conventional, heat pump, number of stages).
• Network Connection: If applicable, connect the thermostat to your Wi-Fi network for remote access and updates.
• Sensor Configuration: If an optional outdoor temperature sensor is installed, ensure it is properly recognized and configured.

Figure 2: Angled view of the Lennox CS7500 Thermostat, highlighting its modern design.

3. Operating Instructions

3.1 Touchscreen Display

The full-color LCD touchscreen displays essential information including the current and set temperature, time, inside relative humidity, system status (operating mode, schedules, and occupancy), and outside temperature (if an optional outdoor sensor is used). Navigate menus and adjust settings by touching the relevant icons or text on the screen.

3.2 Basic Operation

• Adjusting Temperature: Touch the temperature display area and use the up/down arrows or slide controls to set your desired temperature.
• Changing System Mode: Select the system mode icon (e.g., Heat, Cool, Auto, Off) to switch between heating, cooling, automatic changeover, or turning the system off.
• Fan Control: Adjust fan settings (e.g., Auto, On) as needed.

3.3 Programming Schedules

The thermostat offers versatile 7-Day or 5-Day/2-Day programming options. This allows you to create custom comfort and energy-saving schedules for different times of the day and week. Access the scheduling menu to define setpoints for various periods (e.g., Wake, Away, Home, Sleep).

3.4 Energy Saving Features

• One-Touch Away Mode: Activate this mode with a single touch to automatically adjust heating or cooling setpoints to save energy when the building is unoccupied.
• Holiday Scheduling: Allows for a one-touch change to a predefined holiday or special events schedule without needing to reprogram your regular schedule.
• Dual-Fuel Capability: For systems with both gas and electric heating, this feature automatically alternates between the two to optimize efficiency.
• Energy Reports: View reports on how often and for how long the heating or cooling system has operated, providing insights into energy consumption.

3.5 Enhanced Comfort Features

• Automatic Changeover: The thermostat automatically switches between heating and cooling operation based on the indoor temperature to maintain your desired setpoint.
• Smooth Setback Recovery: This function pre-cools or pre-heats a space to reach the desired setpoint temperature precisely when a scheduled period begins, ensuring comfort without delay.
• Built-in Sensors: Integrated temperature and humidity sensors provide accurate readings for optimal climate control.

Figure 3: Close-up of the Lennox CS7500 Thermostat's interactive display.

4. Maintenance

4.1 Reminders

The thermostat features customizable reminders to assist with system maintenance:

• Filter Reminder: Notifies the user when it is time to change the HVAC system's air filter.
• Service and Parts Replacement Reminders: Allows you to set reminders for servicing the system, replacing PureAir metal inserts, humidifier pads, ultraviolet lamps, and two additional user or installer-defined custom reminders. These reminders are displayed on the home screen.

4.2 Cleaning the Thermostat

To clean the touchscreen display, gently wipe it with a soft, damp cloth. Avoid using abrasive cleaners, solvents, or chemical sprays, as these can damage the screen or casing.

5. Troubleshooting

If you encounter issues with your Lennox CS7500 thermostat, consider the following general troubleshooting steps:

• No Power/Blank Screen: Check the circuit breaker for your HVAC system. Ensure the thermostat is properly seated on its base.
• Incorrect Temperature Readings: Verify that the thermostat is not exposed to direct sunlight, drafts, or heat sources that could affect its internal sensor.
• System Not Responding: Ensure the system mode is correctly selected (Heat, Cool, Auto). Check if the fan is set to 'Auto' or 'On' as desired.
• Economizer Fault Detection: The thermostat is designed to detect economizer faults generated by the RTU’s service relay, fulfilling FDD regulations. If a fault is indicated, contact a qualified technician for diagnosis and repair.
• Wi-Fi Connectivity Issues: Ensure your Wi-Fi router is functioning correctly and the thermostat is within range. You may need to re-enter network credentials in the thermostat settings.

For persistent issues or complex problems, it is recommended to contact a certified HVAC technician or Lennox customer support.

6. Specifications

7. Warranty and Support

For information regarding the product warranty, please refer to the warranty documentation included with your purchase or contact the manufacturer directly. For technical support, service, or to locate a certified Lennox dealer, please visit the official Lennox website or contact their customer service department.