Emerson 1E78-151 Thermostat Operation Manual

The Emerson 1E78-151 is a 70 Series 5/2 Day Programmable Thermostat designed for single-stage heating and cooling systems, including conventional gas, oil, electric, or heat pump systems without auxiliary heat. It features a large backlit display, simultaneous heating/cooling program storage, and energy management recovery for optimal comfort and savings. 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. Power Stealing Switches

Key Specifications

Type: Programmable (5/2 day), single-stage thermostat
Compatibility:
- Standard heat only two-wire gas or oil-fired systems (24V)
- Electronic ignition heat only systems (24V)
- Standard heat/cool systems (24V)
- Heat/cool electric heat systems (24V)
- Cool only systems (24V)
- Heat pump systems (no auxiliary or emergency heat)
- Hot water zone heat only (two-wire)
- Not compatible with hot water zone heat only (three-wire), line voltage heating or baseboard 110/240V systems, multistage systems, or systems exceeding 30VAC, 1.5A
Power Source:
- Battery: 2 "AAA" Energizer® alkaline batteries
Electrical Rating:
- Terminal Load: 1.5 A per terminal, 2.5 A max combined
- Rated Differential: 0.6° to 1.9°F with adjustable anticipation
- Setpoint Temperature Range: 45° to 90°F (7° to 32°C)
Display: Backlit 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: 3-7/8” H x 5-1/8” W x 1-1/8” D
Features:
- 5/2 day programming (weekday/weekend) or non-programmable
- 4 time and 4 temperature settings per program for heating and cooling
- Energy savings up to 33%
- Energy Management Recovery (EMR)
- °F/°C convertibility
- Low battery indicator
- Temperature display adjustment
Thermostat Configuration Options:
- Standard heat only two-wire gas or oil-fired systems (24V)
- Electronic ignition heat only systems (24V)
- Standard heat/cool systems (24V)
- Heat/cool electric heat systems (24V)
- Cool only systems (24V)
- Heat pump systems (no auxiliary or emergency heat)
- Hot water zone heat only (two-wire)
- Maximum Stages Heat/Cool: 1/1

Operation Instructions

Initial Setup

1. Insert Batteries: Install 2 “AAA” Energizer® alkaline batteries in the rear compartment, removing the battery tag to activate. Replace when the low battery indicator appears (approximately every 2 years).
2. Power On: The thermostat operates on battery power. 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: EMR (enable/disable by clipping W903), °F/°C (clip W904 for Celsius), hydronic systems (clip W905 for longer heating cycles).
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, 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 any programmed schedule. Press RUN to resume programming if previously set.

Operating in Programmable Mode

1. Factory Schedule: The thermostat is 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 Morning, Day, Evening, and Night 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. Energy Management Recovery (EMR): Enabled by default; starts heating/cooling early to reach setpoint by programmed time. Disable by clipping W903 jumper.
2. Temperature Display Adjustment: Adjust in CONFIGURATION MENU to calibrate display temperature (±3°F) to match actual room temperature.
3. °F/°C Convertibility: Default Fahrenheit; clip W904 jumper for Celsius display.

Hydronic Systems: Clip W905 jumper for longer heating cycles in hot water or steam systems.

Low Battery Indicator: Displays when batteries need replacement; if batteries are not replaced, thermostat may not function properly.

Troubleshooting

No Display: Check battery polarity or replace with fresh AAA alkaline batteries. Verify power supply if hardwired. 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, setpoint is above/below room temperature, and circuit breaker is on. Check for compressor delay (up to 5 minutes). Verify wiring and O/B switch for heat pumps. If no response, contact a professional technician at 1-800-284-2925.
Furnace Cycles Too Often: Clip W905 jumper for hydronic systems to lengthen cycles. Adjust anticipator if applicable, but this model has fixed anticipation.
Inaccurate Temperature: Adjust temperature display in CONFIGURATION MENU (±3°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.
“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, replace it.

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. If the old thermostat contains mercury, wear non-absorbent gloves, clean up any spilled mercury, and place in a sealed container for proper disposal.

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. For single-transformer systems, use RC and RH with the provided jumper wire. For two-transformer systems, clip the jumper and connect RC and RH separately.
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 AAA 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 AAA 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.