Emerson 1F78-144 Thermostat Operation Manual

The Emerson 1F78-144 is a non-programmable, single-stage thermostat designed for conventional gas, oil, electric, or millivolt systems, as well as heat pump systems without auxiliary heat. It features a backlit digital display, simple operation, and energy-saving capabilities. 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. Wiring and Terminal Functions

Key Specifications

Type: Non-programmable, single-stage thermostat
Compatibility:
- Conventional systems (gas, oil, electric, millivolt, 24V)
- Heat pump systems without auxiliary heat
- Heat only, cool only, or heat/cool systems
- Not compatible with electric baseboard heat or systems exceeding 30 VAC
Power Source:
- Battery: 2 AA alkaline batteries (Duracell or Energizer recommended)
- Hardwired: 20-30 VAC, NEC Class II, 50/60 Hz with common (C) wire
Electrical Rating:
- Terminal Load: 0.05 to 1.0 A per terminal, 1.5 A max combined
- Rated Differentials: Heat (0.6°F), Cool (1.2°F)
- Setpoint Range: 45°F to 99°F (7°C to 37°C)
Display: Backlit digital LCD display
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: 3-13/16” H x 5-3/8” W x 1-1/4” D
Features:
- Backlit display with large, easy-to-read temperature
- Adjustable room temperature calibration (±4°F)
- Automatic heat/cool changeover
- Compressor protection (up to 5-minute delay)
- Wall plate (F61-2550, 6.5” W x 4.5” H) to cover marks from previous thermostats
Thermostat Configuration Options:
- Conventional Gas, Oil, Electric (mV and 24V), Heat Only, Cool Only, or Heat/Cool Systems - Maximum Stages Heat/Cool: 1/1
- Heat Pump (Air Source or Geothermal) without Aux. Heat - Maximum Stages Heat/Cool: 1/1

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).
2. Power On: If hardwired, ensure 20-30 VAC is supplied via the C terminal. The display should show the home screen.
3. Configure System:

Locate the GAS/ELECTRIC switch on the back of the thermostat (default: GAS). Set to ELECTRIC for systems requiring the thermostat to control the fan during heating (e.g., electric heat or heat pumps).
Access CONFIGURATION MENU by pressing SYSTEM to OFF, then holding up/down arrows for 5 seconds.
Configure options:
- Item 1: Select heat pump or conventional system.
- Item 2: Select O (cool) or B (heat) for heat pump changeover valve.
- 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, AUTO, or OFF.
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 system should start.
In COOL mode, set temperature 1°F below room temperature; a snowflake icon may flash for up to 5 minutes due to compressor delay, then “Cool On” displays.

Temperature Display Adjustment

1. Access 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.

Troubleshooting

No Display: Check battery polarity or replace batteries. Verify C wire connection for hardwired setups. Reset by pressing up/down arrows and moving SYSTEM switch from OFF to HEAT simultaneously.
No Heat/Cool: Ensure SYSTEM is set to HEAT/COOL, setpoint is above/below room temperature, and circuit breaker is on. Check for compressor delay (up to 5 minutes, indicated by flashing snowflake icon). Verify wiring connections.
Fan Runs Continuously: Set FAN to AUTO. Ensure SYSTEM is not in AUTO mode if only heating or cooling is desired.
Inaccurate Temperature: Calibrate in CONFIGURATION MENU (Item 4). Ensure thermostat is not near drafts, heat sources, or exterior walls.
Erratic Operation: Reset by pressing up/down arrows and moving SYSTEM switch from OFF to HEAT. If the thermostat remains stuck (e.g., fixed at 62°F heat or 85°F cool), perform a reset. If issues persist, contact a professional technician.[](https://www.manualslib.com/manual/194488/White-Rodgers-1f78.html)

Installation Instructions

Warning: Thermostat installation and all components shall conform to Class II circuits per the NEC code. Do not use with line voltage systems; verify wiring with a qualified technician if unsure.

Remove Old Thermostat

Turn off power at the main fuse or circuit breaker until installation is complete.
Remove the front cover of the old thermostat. With wires attached, remove the wall plate. If it has a mounting plate, remove the thermostat and plate as an assembly.
Mark wires for terminal identification using labels provided with the new thermostat.
Disconnect wires one at a time, ensuring they do not fall back into the wall.

Installing New Thermostat

Gently pull the thermostat cover off the 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 and drill mounting holes. Use plastic screw anchors if existing holes are too large.
Fasten base snugly to the wall using two mounting screws. Leveling is for appearance only and does not affect operation.
Connect wires to the terminal block using the appropriate wiring schematic (see Wiring section).
Push excess wire into the wall and plug the hole with fire-resistant material (e.g., fiberglass insulation) to prevent drafts.
Snap the thermostat onto the base carefully.

Battery Location

Includes 2 AA alkaline batteries with a battery tag to prevent power drainage. Remove the tag to engage batteries.
Replace batteries when “LO BATTERY” appears or before leaving the home unoccupied for over 3 months. Use premium brand AA alkaline batteries (e.g., Duracell or Energizer).
Install batteries along the top of the rear compartment, ensuring positive (+) ends are oriented correctly.

Wiring and Terminal Functions

Refer to the equipment manufacturer’s instructions for specific wiring. The following table describes typical terminal functions:

Terminal	Function
RC	Cooling power (24 VAC)
RH	Heating power (24 VAC)
C	Common wire for 24 VAC power from transformer (optional for battery operation)
W	Heat relay
Y	Compressor contactor (cooling)
G	Fan relay
O/B	Heat pump changeover valve (O: cool, B: heat)

Note: For two-wire heat-only systems, connect one wire to RH and the other to W. For single-transformer systems, jumper RC and RH. For heat pumps, set O/B switch to “O” (cool) or “B” (heat) as required by the system. Do not exceed specified voltage ratings. If no C wire is available, the thermostat operates on battery power alone.

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