Setup: 1source S1-THEH21P5S Digital Thermostat Owner Manual

Overview

The S1-THEH21P5S Digital Thermostat is a 5+2 day programmable heat pump thermostat designed for residential systems with one or two stages of heating and one stage of cooling. It can operate from 24-volt system power or two AA alkaline batteries, and its backlit display makes temperature and operating status easier to read.

This thermostat suits homeowners and HVAC technicians who need separate weekday and weekend temperature schedules, manual heat or cool control, auxiliary heat selection, and a service filter reminder.

Specifications

• Model: S1-THEH21P5S
• System type: Heat pump
• Heating and cooling capacity: Up to 2 stages of heat and 1 stage of cooling
• Programming: 5+2 day scheduling with separate weekday and weekend programs
• Power: Two AA alkaline batteries or 24-volt system power
• Display: Backlit digital display with Fahrenheit or Celsius selection
• Fan control: Auto or continuous On
• Auxiliary heat control: Normal, Emergency, and Lockout positions
• Filter reminder: Adjustable blower-runtime notification

Detailed Description

The S1-THEH21P5S Digital Thermostat monitors the room temperature and compares it with the selected heating or cooling setpoint. When the room requires conditioning, the thermostat signals the connected heat pump system. The display shows both the current room temperature and the desired set temperature.

The front controls include COOLER and WARMER buttons, a MODE switch, a FAN switch, a PROGRAM switch, a NEXT button, a RESET FILTER button, and an AUX HEAT switch. The MODE switch selects Cool, Off, or Heat. The FAN switch selects Auto or On. In Auto, the blower runs only when the system calls for heating or cooling; On keeps the blower operating continuously.

The display identifies the active weekday or weekend schedule, current time, time period, heat or cool operation, auxiliary heat activity, low battery status, and filter service status. A flashing Heat or Cool indicator shows that the corresponding function is energized. The AUX HEAT indicator identifies second-stage heating operation.

Safety

• Disconnect power to the heater and air conditioner before removing an existing thermostat or installing this thermostat.
• Follow the installation instructions carefully and have electrical or HVAC work completed by a qualified technician when necessary.
• Replace both AA batteries at least every 12 months. Immediate replacement is required when the low-battery indication appears.
• Annual battery replacement is especially important in areas exposed to freezing temperatures because exhausted batteries may prevent the heating system from starting.
• Keep batteries installed even when the thermostat uses 24-volt power. They can maintain the clock during a power interruption.

Setup and Operation

Set the Time and Day

1. Move the PROGRAM switch to SET.
2. Use the COOLER and WARMER buttons to adjust the flashing time.
3. Press NEXT to move to the day setting.
4. Use the adjustment buttons to select the current day.
5. Press NEXT to continue into the programming screens.

Holding the COOLER or WARMER button changes the time more rapidly.

Manual Heating or Cooling

1. Move the PROGRAM switch to OFF.
2. Set the MODE switch to Heat or Cool.
3. Set the FAN switch to Auto for demand-based blower operation, or On for continuous fan operation.
4. Use COOLER or WARMER to select the desired temperature.

With the PROGRAM switch in OFF, the thermostat operates as a manual heat or cool controller and does not follow stored time periods.

Programmed Operation

The schedule provides four periods for weekdays and four periods for weekends: Morning, Day, Evening, and Night. Each period has a start time, a heating setpoint, and a cooling setpoint.

1. Move the PROGRAM switch to SET.
2. Use COOLER or WARMER to change the flashing time, temperature, or selection.
3. Press NEXT after each item to advance through the schedule.
4. Complete the weekday Morning, Day, Evening, and Night settings.
5. Complete the weekend Morning, Day, Evening, and Night settings.
6. Move the PROGRAM switch to RUN to activate the schedule.

During programmed operation, COOLER and WARMER can temporarily change the active setpoint. The thermostat returns to the programmed settings when the next time period begins.

Auxiliary Heat Modes

• Normal: Allows auxiliary heat to operate with the heat pump when additional heating is needed.
• Emergency: Locks out compressor operation and uses auxiliary heat to satisfy a heating demand. Compressor operation is also locked out during cooling while this position is selected.
• Lockout: Prevents auxiliary heat from operating, regardless of the heating demand.

Advanced Setup

Advanced settings are normally configured by the installer. To enter them, move the PROGRAM switch to SET. When the clock is flashing, press and hold NEXT for five seconds until the advanced setup screen appears.

• Cycles per hour: Adjustable from 2 through 6. A zoning option provides no cycle limit, with an additional setting that removes compressor lockout.
• Backlight: Select Off, 2, 4, 6, or 8 seconds after a button press. An always-on selection is available only when the thermostat is system powered.
• Temperature scale: Select Fahrenheit or Celsius.
• Deadband: Adjust the control deadband from 1 through 6 degrees.
• Filter reminder: Set the blower-runtime threshold from the advanced setup screens. A setting of 0 disables the reminder.

The cycles-per-hour setting limits how often the HVAC equipment may energize. For example, a setting of 6 permits an equipment cycle approximately once every 10 minutes. Pressing COOLER or WARMER can temporarily override this limit.

Two-Stage Heating

Second-stage heat operates when the room temperature falls sufficiently below the heating setpoint. The first-stage deadband is adjustable from 1 through 6 degrees, while the second-stage deadband is fixed at 2 degrees. The AUX HEAT indicator appears when second-stage heating is energized.

Filter Reminder

The filter icon appears after the selected number of blower-runtime hours has accumulated. The counter includes fan operation during heating, cooling, and standalone fan use.

1. Press and hold RESET FILTER.
2. Continue holding until the filter icon disappears and the counter returns to zero.

Replacing or servicing the HVAC filter itself should follow the equipment manufacturer's maintenance instructions.

Restore Factory Defaults

Restoring factory defaults erases stored time-period and advanced programming. Use this procedure only when a complete reset is intended.

1. Move the PROGRAM switch to SET.
2. When the clock flashes, press and hold NEXT for five seconds to enter advanced setup.
3. When Cycles Per Hour flashes, press and hold NEXT until the reset screen appears.
4. Press and hold NEXT again to restore the factory settings.
5. Move the PROGRAM switch to OFF or RUN to return to normal operation.

The display shows all icons after the reset process. Previously entered schedules and advanced settings are permanently cleared.

Temperature Calibration

Calibration is normally unnecessary. If the displayed room temperature requires adjustment, the procedure should be performed by a trained HVAC technician.

1. Move the PROGRAM switch to SET.
2. When the clock flashes, press and hold NEXT for five seconds to enter advanced setup.
3. Press NEXT twice to reach the calibration screen.
4. Use COOLER or WARMER to adjust the temperature reading.
5. Press NEXT to store the new calibration value.
6. Move the PROGRAM switch to OFF or RUN.

Replace the Batteries

1. Press down on the battery cover at the front of the thermostat.
2. Pull the battery compartment outward.
3. Remove both old batteries.
4. Install two new AA alkaline batteries in the correct orientation.
5. Insert the bottom hook of the cover into its slot.
6. Snap the cover closed.

Replace the batteries immediately when the low-battery icon appears. If the thermostat is powered by 24 volts, retain the batteries so the clock can continue operating during a power interruption.

Troubleshooting

• The display shows a low-battery indication: Replace both AA alkaline batteries immediately.
• The heating system does not start: Check that the MODE switch is set to Heat, the desired temperature is above the room temperature, and the PROGRAM switch is in the intended position.
• The cooling system does not start: Check that the MODE switch is set to Cool and that the desired temperature is below the room temperature.
• The fan runs continuously: Move the FAN switch from On to Auto if continuous blower operation is not desired.
• The schedule is not operating: Move the PROGRAM switch to RUN. The OFF position disables programmed operation.
• Auxiliary heat does not operate: Check whether the AUX HEAT switch is set to Lockout. In that position, auxiliary heat is prevented from turning on.
• The compressor does not operate in Emergency mode: This is expected. Emergency mode intentionally disables compressor functions and uses auxiliary heat.
• The filter icon remains visible: Press and hold RESET FILTER after servicing the filter to clear the reminder and reset its runtime counter.
• Temperature control cycles too frequently: Have the installer review the Cycles Per Hour and deadband settings for the connected HVAC system.

Warranty

The S1-THEH21P5S includes a one-year limited warranty against defects in materials and workmanship from the date of original installation. The stated coverage applies to the product at its original installation location and provides a replacement part, at the manufacturer's option, when the warranty conditions are met.

The warranty does not cover labor or other costs associated with diagnosis, removal, installation, shipping, servicing, or handling. It also excludes routine maintenance, incorrect installation, misuse, unauthorized alterations, electrical service problems, environmental damage, non-approved parts, fuel or electricity costs, and certain indirect or consequential losses. Replacement parts carry only the remaining portion of the original warranty period.

Pros & Cons

• Pros: Supports two-stage heat pump operation, offers separate weekday and weekend schedules, includes emergency and auxiliary heat controls, provides battery or system-powered operation, and displays a configurable filter reminder.
• Cons: Programming uses physical switches and buttons rather than a touchscreen, advanced configuration may require an HVAC technician, and batteries still need regular replacement even when 24-volt power is connected.