Emerson 1E78-140 Thermostat Operation Manual

The Emerson 1E78-140 is a non-programmable, heat-only thermostat designed for single-stage heating systems, including gas, oil, or millivolt systems. It features a backlit digital display, simple operation, and precise temperature control, ideal for fireplaces, garage heaters, or other heat-only applications. 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, single-stage heat-only thermostat
Compatibility:
- Single-stage heating systems (gas, oil, millivolt, 24V)
- Hydronic (hot water or steam) systems
- Gas fireplaces, garage heaters, or unit heaters
- Not compatible with cooling systems, electric baseboard heat, or systems exceeding 30 VAC
Power Source:
- Battery: mV to 30 VAC, NEC Class II, 50/60 Hz or DC (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 1.0 A per terminal, 1.5 A max combined
- Rated Differential: Heat (@ 6°F/Hr): Fast 0.5°F, Medium 0.75°F, Slow 1.9°F
- Setpoint Range: 45°F to 90°F (7°C to 32°C)
Display: Backlit LCD display, adjustable ±3°F
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:
- Backlit display with large, easy-to-read temperature
- Adjustable temperature calibration
- Vertical 70 Series low-profile design
- Optional wall plate (F61-2550, 6.5” W x 4.5” H) to cover marks from previous thermostats
Thermostat Configuration Options:
- Single-Stage Heat Only: Gas, Oil, Millivolt, Hydronic Zone (Hot Water or Steam) Systems, 24 Volt or Millivolt - Maximum Stages Heat: 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 jumper W905 on the circuit board (default: intact for forced-air heat). Clip W905 for hydronic (hot water or steam) systems to produce a longer heating cycle (approximately 1.5°F differential).
Access CONFIGURATION MENU by pressing SYSTEM to OFF, then holding up/down arrows for 5 seconds.
Configure options:
- Temperature display (°F or °C).
- Temperature calibration (±3°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 or OFF.
2. Adjust Temperature: Press up/down arrows to set the desired temperature.
3. Verify Operation: In HEAT mode, set temperature 1°F above room temperature; “Heat On” or a flame icon should display, and the heating system should start. If the flame icon stays on constantly, it may indicate a display issue rather than heater status; verify system operation manually.
Note: This thermostat does not control cooling or fan functions.

Temperature Display Adjustment

1. Access CONFIGURATION MENU (SYSTEM to OFF, hold up/down arrows for 5 seconds).
2. Navigate to Temperature Display Adjustment.
3. Use up/down arrows to adjust the displayed temperature by ±3°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 with fresh AAA alkaline batteries. Verify C wire connection for hardwired setups. Reset by removing batteries for 2 minutes. If no power reading with a multimeter, check for loose wiring or a blown fuse.
No Heat: Ensure SYSTEM is set to HEAT, setpoint is above room temperature, and circuit breaker is on. For gas systems, verify the pilot is lit. Check wiring (e.g., RH and W for two-wire systems). If no response, test continuity between W wire and limit switch using a multimeter.
Flame Icon Constantly On: The flame icon may remain on after switching to HEAT, not indicating heater status. Verify actual heater operation. If the icon persists without heat, reset the thermostat or replace if defective.
Inaccurate Temperature: Calibrate in CONFIGURATION MENU (±3°F). Ensure thermostat is not near drafts, heat sources, or exterior walls.
Erratic Operation: A voltage spike or static discharge may cause issues. Reset by removing batteries for 2 minutes or installing them backward for 5 seconds, then correctly. If issues persist, the thermostat may need replacement.
Buttons Not Working: Replace batteries and perform a reset. If up/down buttons remain unresponsive, contact a professional technician.

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.

Remove Old Thermostat

Before removing wires, mark wires for terminal identification to ensure proper connections to the new thermostat. For mercury-containing thermostats, handle carefully, wear non-absorbent gloves, and dispose of properly per local regulations.

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 (typically RH and W for two-wire heat-only systems).
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 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). If incompatible, set switches to “Off” to operate on batteries.