1. Introduction
This manual provides comprehensive instructions for the installation, operation, and maintenance of your ProSelect SL21NP Digital Non-Programmable Thermostat. This device is designed to provide reliable temperature control for your heating and cooling systems. Please read this manual thoroughly before installation and operation to ensure proper function and safety.
Key Features:
- Large 2 Sq. In. backlight display for easy viewing and setting adjustments.
- Fully adjustable temperature limits for customization.
- Hardwired design with battery backup ensures operation during power loss.
- Settings are retained in permanent memory.
- Short cycle protection to prevent AC compressor damage.
- Low battery indicator for timely battery replacement.
- Fahrenheit/Celsius switch for preferred temperature format.
- Compatible with electric or gas fans with a built-in toggle switch.
- Auto Changeover feature.
2. Safety Information
WARNING: Always turn off power to the heating/cooling system at the main fuse or circuit breaker panel before installing or servicing the thermostat. Failure to do so could result in electrical shock or equipment damage.
- Read all instructions carefully before installation.
- Installation should be performed by a qualified technician if you are unsure about any steps.
- Ensure all wiring connections are secure and comply with local electrical codes.
- Do not operate the thermostat with wet hands.
- Keep the thermostat away from direct sunlight, drafts, and heat sources that could affect temperature readings.
3. Product Overview
The ProSelect SL21NP thermostat features a clear digital display and intuitive controls for managing your home's climate.
Figure 1: Front view of the ProSelect SL21NP Thermostat. It shows the large digital display indicating room temperature and "COOL ON", along with "SET AT" temperature. Below the display are the SYSTEM mode switch (COOL, OFF, HEAT, EMER) and FAN mode switch (AUTO, ON). A 'RESET' button is visible on the left, and up/down adjustment buttons are on the right.
Component Identification:
- Digital Display: Shows current room temperature, set temperature, system status (COOL ON), and fan status.
- Up/Down Buttons: Used to adjust the set temperature.
- SYSTEM Switch: Selects the operating mode: COOL, OFF, HEAT, or EMER (Emergency Heat).
- FAN Switch: Selects fan operation mode: AUTO (fan runs only when heating/cooling) or ON (fan runs continuously).
- RESET Button: Recessed button to reset the thermostat to factory defaults.
- Battery Compartment: (Typically on the back or side) For backup batteries.
4. Installation and Setup
This thermostat is designed for easy installation. However, if you are unfamiliar with electrical wiring, it is recommended to seek professional assistance.
Pre-Installation Checklist:
- Ensure the power to your heating/cooling system is turned off at the circuit breaker.
- Gather necessary tools: screwdriver, wire strippers, drill (if mounting new holes).
- Read the wiring diagram provided with your specific unit (not included in this general manual).
Mounting and Wiring:
- Carefully remove your old thermostat, noting the wire connections. Label wires if necessary.
- Mount the new thermostat's backplate to the wall using the provided screws.
- Connect the wires to the corresponding terminals on the new thermostat. This model is compatible with electric or gas fans and supports 2 Heat / 1 Cool stages.
- Insert backup batteries (if applicable) into the battery compartment.
- Attach the thermostat front to the mounted backplate.
- Restore power to your heating/cooling system at the circuit breaker.
Initial Setup:
- Upon power-up, the thermostat will display the current room temperature.
- Use the Fahrenheit/Celsius switch (usually located on the back or inside the unit) to select your preferred temperature format.
- The thermostat retains settings in permanent memory, so initial setup is minimal.
5. Operation
Setting the Temperature:
- Press the Up or Down arrow buttons located on the right side of the display to adjust the desired set temperature. The "SET AT" temperature will flash as you adjust it and then stabilize after a few seconds.
- The thermostat will automatically activate your heating or cooling system to maintain the set temperature.
System Mode Selection:
Use the SYSTEM switch located at the bottom left of the thermostat to select the desired operating mode:
- COOL: Activates the cooling system when the room temperature rises above the set temperature.
- OFF: Turns off both heating and cooling systems.
- HEAT: Activates the heating system when the room temperature falls below the set temperature.
- EMER (Emergency Heat): (If applicable to your system) Activates auxiliary or emergency heating.
Fan Mode Selection:
Use the FAN switch located at the bottom right of the thermostat to select the desired fan operation:
- AUTO: The fan runs only when the heating or cooling system is actively operating. This is the most common and energy-efficient setting.
- ON: The fan runs continuously, regardless of whether the heating or cooling system is active.
Additional Features:
- Backlight Display: The display is backlit for easy viewing in low-light conditions.
- Short Cycle Protection: This feature prevents damage to your AC compressor by delaying the compressor from restarting too quickly after it has just turned off.
- Low Battery Indicator: A low battery icon will appear on the display when the batteries need to be replaced.
6. Maintenance
Battery Replacement:
Although the thermostat is hardwired, it uses batteries for backup power and to retain settings during power outages. When the low battery indicator appears on the display:
- Gently remove the thermostat from its wall plate.
- Locate the battery compartment (usually on the back).
- Replace the old batteries with new alkaline batteries of the specified type (e.g., AA or AAA, check the unit for exact type).
- Reattach the thermostat to the wall plate.
Cleaning:
To clean the thermostat, gently wipe the exterior with a soft, damp cloth. Do not use abrasive cleaners or solvents. Avoid spraying liquids directly onto the thermostat.
7. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Display is blank or dim. | No power from system; dead backup batteries. | Check circuit breaker; replace backup batteries. |
| Heating/Cooling system not responding. | System switch in OFF position; incorrect wiring; power issue. | Set system switch to HEAT or COOL; verify wiring connections; check circuit breaker. |
| Temperature reading seems inaccurate. | Thermostat exposed to drafts, direct sunlight, or heat sources. | Relocate thermostat if possible; ensure no obstructions. |
| Thermostat not holding set temperature. | System capacity issues; external factors affecting room temperature. | Consult with an HVAC professional; ensure windows/doors are sealed. |
| Thermostat needs to be reset. | Software glitch or unexpected behavior. | Press the recessed RESET button with a small pointed object (e.g., paperclip). |
8. Specifications
| Feature | Detail |
|---|---|
| Model Number | PSTSL21NP |
| Control Type | Electronic, Button Control |
| Display Size | 2 Inches (Square Inch Area Display) |
| Backlight | Yes |
| Programmable | No (Non-Programmable) |
| Stages | 2 Heat / 1 Cool |
| Temperature Range (Min) | 45°F (7°C) |
| Temperature Range (Max) | 90°F (32°C) |
| Voltage | 24 Volts |
| Amperage | 3 Amps |
| Dimensions (L x W x H) | 3.51 x 11.99 x 9.19 cm (approx. 1.38 x 4.72 x 3.62 inches) |
| Item Weight | 249.48 g (approx. 0.55 lbs) |
| Color | White |
| Special Features | Auto Changeover |
9. Warranty and Support
Warranty Information:
The ProSelect SL21NP Digital Non-Programmable Thermostat comes with a 5-year limited warranty for the original owner. This warranty covers defects in materials and workmanship under normal use. Please retain your proof of purchase for warranty claims.
Customer Support:
For technical assistance, troubleshooting beyond this manual, or warranty inquiries, please contact ProSelect customer support. Refer to the product packaging or the manufacturer's official website for the most current contact information.
