Emerson 1F78-151 Thermostat Operation Manual

The Emerson 1F78-151 is a 5+2 day 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, easy programming, and energy-saving settings for efficient temperature control. Below are the key specifications and operation instructions.

1. Key Specifications 2. Operation Instructions 2.1. Initial Setup 2.2. Setting the Clock and Day 2.3. Operating in Non-Programmable Mode 2.4. Operating in Programmable Mode 2.5. Advanced Features 2.6. 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: Programmable (5+2 day), 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 multi-stage systems, electric baseboard heat, or systems exceeding 30 VAC
Power Source:
- Battery: 2 AAA alkaline batteries (Duracell or Energizer recommended)
- Hardwired: 20-30 VAC, NEC Class II, 50/60 Hz with common (C) wire (optional)
Electrical Rating:
- Terminal Load: 0.05 to 1.5 A per terminal, 1.5 A max combined
- Rated Differentials: Heat (0.6°F to 1.9°F, adjustable), Cool (1.2°F)
- Setpoint Range: 45°F to 90°F (7°C to 32°C)
Display: Backlit digital LCD display (backlight off by default, activated by pressing TIME and RUN simultaneously)
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 5-1/8” W x 1-1/8” D
Features:
- 5+2 day programming (Mon-Fri, Sat-Sun) with 4 time/temperature settings per day
- Backlit display for low-light conditions
- Filter change indicator (0 to 1950 hours, adjustable)
- Automatic heat/cool changeover
- Temporary temperature override
- Compressor protection (up to 5-minute delay)
- Wall plate (F61-2550, 6.5” W x 4.5” H) to cover marks from previous thermostats
- Selectable Celsius or Fahrenheit display
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 AAA 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 (optional). 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 5: Filter change reminder (0 to 1950 hours, 0 to disable).
Exit by pressing RUN or waiting for the display to return to normal.

Setting the Clock and Day

1. Press TIME button.
2. Use up/down arrows to adjust hours, minutes, and AM/PM.
3. Press TIME again to set the day of the week, using up/down arrows to select.
4. Press RUN to save and exit.

Operating in Non-Programmable Mode

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. Manual Operation: Press HOLD to maintain a constant temperature, bypassing the programmed schedule. Press RUN to resume programming.

Operating in Programmable Mode

1. Factory Schedule: Pre-programmed with energy-saving settings (e.g., Heat: 70°F day, 62°F night; Cool: 78°F day, 82°F night). Press RUN to use defaults.
2. Custom Schedule:

Press PRGM, then select HEAT or COOL.
Choose weekday (Mon-Fri) or weekend (Sat-Sun) programming.
Set times/temperatures for Wake, Leave, Return, and Sleep periods using TIME and up/down arrows.
Save by pressing RUN.

3. Temporary Override: Press up/down arrows to adjust temperature; it holds until the next programmed period.
4. Permanent Hold: Press HOLD to maintain a set temperature until RUN is pressed.
5. Disable Programming: In CONFIGURATION MENU, set programming to non-programmable mode if desired.

Advanced Features

1. Filter Change Reminder: Alerts when filter replacement is needed (set in CONFIGURATION MENU, Item 5). Reset by pressing up/down arrows simultaneously in CONFIGURATION MENU.
2. Compressor Protection: Automatically delays compressor restart (up to 5 minutes) to prevent damage, indicated by a flashing snowflake icon.
3. Backlight Activation: Press TIME and RUN simultaneously to enable/disable the backlight for low-light conditions.

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.
“FILTER” Displayed: Indicates filter replacement needed. Clear by pressing up/down arrows in CONFIGURATION MENU (Item 5).
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.

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 AAA 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 AAA 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	Heat pump changeover valve (energized in cooling)
B	Heat pump changeover valve (energized in heating)

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. The thermostat can operate on battery power if no C wire is available. Do not exceed specified voltage ratings.