Emerson 1F79-111 Thermostat Operation Manual

The Emerson 1F79-111 is a 70 Series Non-Programmable Heat Pump Thermostat designed for heat pump systems (2H/1C) with or without auxiliary/emergency heat. It features a large, backlit digital display, precise temperature control, and easy installation for battery-powered or hardwired setups. Below are the key specifications and operation instructions.

1. Key Specifications 2. Operation Instructions 2.1. Initial Setup 2.2. Operating the Thermostat 2.3. Temperature Display Adjustment 2.4. Troubleshooting 3. Installation Instructions 3.1. Remove Old Thermostat 3.2. Installing New Thermostat 3.3. Battery Location 3.4. Power Stealing Switches

Key Specifications

Type: Non-programmable heat pump thermostat
Compatibility:
- Heat pump systems (2H/1C, with or without auxiliary/emergency heat)
- Not compatible with conventional gas, oil, electric systems, millivolt heat-only systems, standard central air conditioning, or systems exceeding 30 VAC
Power Source:
- Battery: mV to 30 VAC, NEC Class II, 50/60 Hz (2 AA alkaline batteries, Duracell or Energizer recommended)
- Hardwired: 20-30 VAC, NEC Class II, 50/60 Hz with common (C) wire
- Power Stealing Assist for systems without C wire
Electrical Rating:
- Terminal Load: 1.0 A per terminal, 1.5 A max combined
- Rated Differentials (@ 6°F/Hr):
  - Heat Pump (Heat): Fast 0.9°F, Medium 1.2°F, Slow 1.7°F
  - Heat Pump (Cool): Fast 0.9°F, Medium 1.2°F, Slow 1.7°F
  - Auxiliary Heat: Fast 0.5°F, Medium 0.75°F, Slow 1.9°F
- Setpoint Range: 45°F to 99°F (7°C to 37°C)
Display: Large backlit LCD display for low-light viewing
Operating Conditions:
- Ambient: 32°F to 105°F (0°C to 41°C)
- Humidity: 90% non-condensing max
- Shipping: -4°F to 150°F (-20°C to 65°C)
Dimensions: 5.1” W x 3.7” H x 1.1” D
Features:
- Large, easy-to-read backlit display
- Adjustable room temperature calibration
- Compressor lockout (optional 5-minute delay)
- System switch: Heat, Off, Cool, Emergency
- Hardwired with battery backup
- Replaces older models like 1F58-72 and 1F58W-72
Thermostat Configuration Options:
- Heat Pump (No Aux or Emergency Heat) - Maximum Stages Heat/Cool: 1/1
- Heat Pump (with Aux or Emergency Heat) - Maximum Stages Heat/Cool: 2/1

Operation Instructions

Initial Setup

1. Insert Batteries: Install 2 AA alkaline batteries in the rear compartment, removing the battery tag to activate. Replace when “LO BATTERY” appears (approximately every 2 years). If the home is unoccupied for over 3 months and the battery indicator shows low, replace batteries before leaving.
2. Power On: If hardwired, ensure 20-30 VAC is supplied via the C terminal. The display should show the home screen with temperature and system status.
3. Configure System:

Locate the O/B switch on the thermostat base (default: O). Set to O for heat pumps energizing the changeover relay in COOL, or B for energizing in HEAT.
Access INSTALLER/CONFIGURATION MENU by pressing SYSTEM to OFF, then holding up/down arrows for 5 seconds.
Configure options:
- Item 1: Fast second-stage heat (FA ON/OFF). If ON, second stage energizes immediately when setpoint is raised 3°F (2°C) or more; if OFF, delays 10 minutes.
- Item 2: Compressor lockout (CL ON/OFF). If ON, enforces a 5-minute delay between compressor cycles to protect the compressor.
- Item 3: Temperature display (°F or °C).
- Item 4: Temperature calibration (±4°F).
Exit by pressing RUN or waiting for the display to return to normal.

Operating the Thermostat

1. Select Mode: Press SYSTEM to choose HEAT, COOL, EMER (emergency heat for heat pumps), or OFF. EMER bypasses the heat pump to use the auxiliary heat source wired to terminal E.
2. Adjust Temperature: Press up/down arrows to set the desired temperature.
3. Fan Control: Press FAN to select AUTO (runs with heating/cooling) or ON (continuous).
4. Verify Operation:

In HEAT mode, set temperature 1°F above room temperature; “Heat On” should display, and the heat pump should start. If flame and snowflake icons flash, compressor lockout is active (Item 2).
In COOL mode, set temperature 1°F below room temperature; “Cool On” should display after up to a 5-minute compressor delay (indicated by flashing snowflake icon).
In EMER mode, set temperature above room temperature; “EMER” flashes, and auxiliary heat should start, with the flame icon flashing.

Temperature Display Adjustment

1. Access INSTALLER/CONFIGURATION MENU (SYSTEM to OFF, hold up/down arrows for 5 seconds).
2. Navigate to Item 4 (Temperature Calibration).
3. Use up/down arrows to adjust the displayed temperature by ±4°F to match the actual room temperature.
4. Press RUN to save and exit.
Note: Use a separate thermometer for calibration. Relocate the thermostat if near drafts, heat sources, or exterior walls (recommended placement: 1.5 meters above the floor, in a frequently used room).

Troubleshooting

No Display: Check battery polarity or replace with fresh AA alkaline batteries. Verify C wire connection for hardwired setups. Reset by removing batteries for 2 minutes or installing them backward for 5 seconds, then correctly. If the display remains blank, clean battery contacts with a pencil eraser or check for a blown fuse.
No Heat/Cool: Ensure SYSTEM is set to HEAT/COOL/EMER, setpoint is above/below room temperature, and circuit breaker is on. Check for compressor lockout (up to 5 minutes, indicated by flashing flame/snowflake icons). Verify O/B switch setting and wiring (especially E for EMER mode). If no response, bypass thermostat by connecting R, G, and Y wires to test system; if the system works, replace the thermostat. Contact a professional technician at 1-800-284-2925 if needed.
Furnace Cycles Too Often: In INSTALLER/CONFIGURATION MENU, set fast second-stage (Item 1) to OFF for delayed auxiliary heat engagement. Ensure O/B switch matches system requirements.
Inaccurate Temperature: Calibrate in INSTALLER/CONFIGURATION MENU (Item 4, ±4°F). Ensure thermostat is not near drafts, heat sources, or exterior walls.
Fan Runs Continuously: Set FAN to AUTO. If the fan persists, check wiring for shorts in the G terminal. Ensure SYSTEM is not in AUTO mode if only heating or cooling is desired.
“LO BATTERY” Persists After Replacement: Clean battery contacts with a pencil eraser. Remove thermostat from base, wait 30 seconds, and reattach. If issues persist, the thermostat may be faulty; contact a technician.
Erratic Operation: Reset by removing batteries for 2 minutes. If the thermostat remains unresponsive or displays incorrect modes, verify wiring and system compatibility.

Installation Instructions

Warning: Thermostat installation and all components of the control system shall conform to Class II circuits per the NEC code. To prevent electrical shock or equipment damage, disconnect power at the main fuse or circuit breaker before installation. If replacing a thermostat containing mercury, do not discard in household trash; follow local disposal regulations.

Remove Old Thermostat

Before removing wires, mark wires for terminal identification to ensure proper connections to the new thermostat. Take a picture of the wiring for reference. Gently pull the cover straight off the base; do not force or pry to avoid damage.

Installing New Thermostat

Pull the thermostat body off the thermostat base. Do not force or pry to avoid damage.
Place base over the hole in the wall and mark mounting hole locations using the base as a template.
Move base out of the way, drill mounting holes. Use plastic screw anchors if existing holes are too large.
Fasten base snugly to the wall using mounting holes and two mounting screws. Leveling is for appearance only and does not affect operation.
Connect wires to the terminal block on the base using the appropriate wiring schematic. Take care to avoid shorting wires to adjacent terminals or the rear of the thermostat to prevent personal injury or property damage.
Push excess wire into the wall and plug the hole with fire-resistant material (e.g., fiberglass insulation) to prevent drafts.
Carefully line the thermostat up with the base and snap into place.

Battery Location

Includes 2 AA alkaline batteries at the factory with a battery tag to prevent power drainage. Remove the tag to engage batteries.
To replace, set system to OFF, remove thermostat from the wall, and install batteries in the rear along the top. Use premium brand AA alkaline batteries like Duracell or Energizer.
If the home will be unoccupied for over 3 months and the battery level indicator shows low, replace batteries before leaving.

Power Stealing Switches

Leave switches in the “On” position for most systems. Details in the following table:

Thermostat Power Method	Switch Position/Description
Battery Powered, no 24 Volt system	Switches “On”, thermostat runs on batteries.
Hardwired with Battery Back-up, for 24 Volt systems with common connection from transformer to “C” terminal	Switches “On”, thermostat runs on power directly from transformer with battery back-up.
Battery Powered with Power Stealing Assist, for 24 Volt systems with no common connection	Switches “On”, thermostat runs on batteries and supplemental power drawn through heat or cool circuit.

Caution: Power Stealing Assist may cause issues on systems with high impedance electronic modules (e.g., furnace draft inducer motor running with no call for heat, furnace fan not turning off). If incompatible, set switches to “Off” to operate on batteries.