The White Rodgers 1F78 is a non-programmable thermostat for heating and air conditioning systems. It features a digital display, manual temperature adjustment, and compatibility with various 24V HVAC systems including gas, oil, electric heat, and single-stage heat pumps. Requires 2 AAA batteries. Below are the key specifications, installation, operation, and troubleshooting instructions.
| System Type | Compatibility |
|---|---|
| Standard Heat Only Two Wire Gas or Oil Fired Systems (24 volt) | Yes |
| Electronic Ignition Heat Only Two Wire Systems (24 volt) | Yes |
| Electronic Ignition Heat Only Gas or Oil Fired Systems (24 volt) | Yes |
| Standard Heat/Cool Systems (24 volt) | Yes |
| Heat/Cool Systems Electric Heat (24 volt) | Yes |
| Heat Only Electric Heat Systems (24 volt) | Yes |
| Cool Only Systems (24 volt) | Yes |
| Heat Pump Systems (No Aux or Emergency Heat) | Yes |
| Hot Water Zone Heat Only (Two Wire) Systems | Yes |
| Hot Water Zone Heat Only (Three Wire) Systems | No |
| Line Voltage Heating or Baseboard 110/240 Volt Systems | No |
| Millivolt Systems Floor or Wall Furnaces | Yes |
| 12 VDC Mobile Home Application | Yes |
| Multistage Systems | No |
| Systems Exceeding 30VAC, 1.5 Amp | No |
Assemble tools required: hand or power drill with 3/16 inch drill bit (if needed), flat blade screwdriver, wire cutter/stripper.
WARNING: Failure to follow and read all instructions carefully before installing or operating this control could cause personal injury and/or property damage.
ATTENTION: This product does not contain mercury. However, this product may replace a unit which contains mercury. Do not open mercury cells. If a cell becomes damaged, do not touch any spilled mercury. Wearing non-absorbent gloves, take up the spilled mercury and place into a container which can be sealed. Mercury must not be discarded in household trash. Refer to www.white-rodgers.com for location to send product containing mercury.
The 1F78 thermostat includes terminals for RH, RC, G, W, Y, O, B; Electric/Gas switch; clips for Celsius display (W904) and Hydronic system (W905); requires 2 AAA batteries.
Figure 1 Description: Thermostat base with mounting holes, terminals labeled RH, RC, G, O, Y, B, W, +, -, Electric/Gas Switch.
Electric Heat or Single-Stage Heat Pump Systems: This thermostat is configured from the factory to operate a heat/cool, fossil fuel (gas, oil, etc.), forced air system. It is configured correctly for any system that DOES NOT require the thermostat to energize the fan on a call for heat. If your system is an electric or heat-pump system that REQUIRES the thermostat to turn on the fan on a call for heat, locate the GAS/ELECTRIC switch and switch it to the ELECTRIC position. This will allow the thermostat to energize the fan immediately on a call for heat. If you are unsure if the heating/cooling system requires the thermostat to control the fan, contact a qualified heating and air conditioning service person.
Hydronic (Hot Water or Steam) Heating Systems: This thermostat is set to operate properly with a forced-air heating system. If you have a hydronic heating system (a system that heats with hot water or steam), you must set the thermostat to operate properly with your system. The factory default setting is forced air heat. Clipping jumper W905 on the circuit board will produce a longer heating cycle which is normally for hot water or steam (hydronic) systems. Both settings produce a very accurate temperature control and can be set to your personal preference. As received, the thermostat cycles the system just under 1°F. With W905 clipped, the system cycles at approximately 1.5°F.
| New Thermostat Terminal Designation | Other Manufacturers’ Terminal Designation |
|---|---|
| RH | 4, R |
| RC | G |
| G | W |
| W | Y |
| Y | RH, R, G, W, Y, M, V, F, H, C, R5, -, G, 4, Y6, R, - |
* These are four-wire, single-transformer systems. Factory installed jumper wire between the RH and RC terminals must remain in place.
Figure 2 Description: Typical wiring diagram for heat only, 3-wire, single transformer systems. Connections to RH, W; note for 2-wire heat only attach to RH and W.
Figure 3 Description: Typical wiring diagram for cool only, 3-wire, single transformer systems. RED jumper wire must be used on single transformer systems.
Figure 4 Description: Typical wiring diagram for heat/cool, 4-wire, single transformer systems. Jumper between RH and RC.
Figure 5 Description: Typical wiring diagram for heat/cool, 5-wire, two-transformer systems.
Figure 6 Description: Typical wiring diagram for heat pump with reversing valve energized in COOL. Jumper wires on O/B and Y.
Figure 7 Description: Typical wiring diagram for heat pump with reversing valve energized in HEAT.
NOTE: To prevent static discharge problems, touch side of thermostat to release static build-up before touching any keys. If at any time during testing your system does not operate properly, contact a qualified service person.
If your system does not have a G terminal connection, skip to Heating System.
CAUTION: To prevent compressor and/or property damage, if the outdoor temperature is below 50°F, DO NOT operate the cooling system.
This thermostat has a time delay between cooling cycles to allow the head pressure in the compressor to stabilize. If the temperature is adjusted to call for cool within 5 minutes of the last cycle the snowflake icon will blink indicating the thermostat is locked out. After 3 to 5 minutes, the compressor will start and the snowflake icon will stop flashing. This helps prevent the compressor from cycling too quickly and is normal operation for the thermostat.
Before you begin using your thermostat, you should be familiar with its features and with the display and the location and operation of the thermostat buttons. Your thermostat consists of two parts: the thermostat cover and the base. To remove the cover, gently pull it straight out from the base. To replace the cover, line up the cover with the base and press gently until the cover snaps onto the base.
The Thermostat Buttons and Switches:
The Display:
Reset Operation: If a voltage spike or static discharge blanks out the display or causes erratic thermostat operation you can reset the thermostat by pressing up and down arrows at the same time while moving the SYSTEM switch from OFF to HEAT. This also resets the factory defaults. If the thermostat has power, has been reset and still does not function correctly contact your heating/cooling service person or place of purchase.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| No Heat/No Cool/No Fan (common problems) | 1. Blown fuse or tripped circuit breaker. 2. Furnace power switch to OFF. 3. Furnace blower compartment door or panel loose or not properly installed. | 1. Replace fuse or reset breaker. 2. Turn switch to ON. 3. Replace door panel in proper position to engage safety interlock or door switch. |
| No Heat | 1. Pilot light not lit. 2. Broken or melted anticipator wire. 3. Loose connection to thermostat or system. 4. Thermostat or heating system requires replacement or service. 5. SYSTEM Switch not set to HEAT. | 1. Re-light pilot. 2. Excessive current or dead short in system. Have a qualified service person check the system before replacing thermostat. 3. Verify thermostat and system wires are securely attached. 4. Your furnace manufacturer or service person can describe how to test the heating system to verify it is operating correctly. If the heating system is capable of operation and the no heat condition persists, replace the thermostat. 5. Set SYSTEM Switch to HEAT and raise temp above room temp. |
| No Cool | 1. Loose connection to thermostat or system. 2. Thermostat or cooling system requires replacement or service. 3. SYSTEM Switch not set to COOL. | 1. Verify thermostat and system wires are securely attached. 2. Your cooling system manufacturer or service person can describe how to test the cooling system to verify it is operating correctly. If the cooling system is capable of operation and the no cooling condition persists, replace the thermostat. 3. Set SYSTEM Switch to COOL and lower temp below room temp. |
| Heat, Cool or Fan Runs Constantly | 1. Possible short in wiring. 2. Possible short in thermostat. 3. Possible short in heat/cool/fan system. | Check each wire connection to the thermostat to verify it is neatly looped under the terminals. No extra wire should stick out from under the terminals. |
| Furnace Cycles Too Fast or Too Slow (narrow or wide temperature swing) | The cycle rate is fixed. The location of the thermostat, size of the Heat/Cool System and current draw can influence the cycle rate. Contact a local service person for additional suggestions. | |
| Cooling Cycles Too Fast or Too Slow (narrow or wide temperature swing) | 1. Poor thermostat location for sensing room temperature. 2. Cooling system over or undersized. 3. Excessive Current draw influencing thermostat. | The cycle rate for cooling can not be adjusted. The location of the thermostat, size of the Cool system and current draw can influence the cycle rate. Contact a local service person for suggestions. |
| Thermostat Setting and Thermostat Thermometer Disagree | 1. Thermostat thermometer setting requires adjustment. | The thermometer can be adjusted by using a standard slotted screwdriver. Turn the thermometer pointer screw located inside the front cover to change the setting. For calibrating the setting lever contact a local heating and cooling service person. |
| Blank Display and/or Keypad Not Responding | Battery or RC wire problem. | Replace batteries and check heat/cool system for proper operation. If a voltage spike occurs use the Reset Operation listed above. |