The White Rodgers 1F90-51 is a non-programmable electronic digital thermostat for single-stage heating and cooling systems, including gas, oil, electric, and single-stage heat pumps. It features precise temperature control, filter timer, and easy operation with large display. Powered by 24 VAC system; compatible with systems up to 1.5A total load. Below are the key specifications, installation, operation, and troubleshooting instructions.
Assemble tools: hand or power drill with 3/16 inch drill bit (if needed), flat blade screwdriver, wire cutter/stripper, level. Shut off electricity at main fuse box until installation complete. Label wires before disconnecting. This thermostat is for 24V systems only; not for line voltage. Install away from drafts, direct sunlight, or heat sources for accurate sensing.
WARNING! Failure to read and follow all instructions carefully before installing or operating this control could cause personal injury and/or property damage. Save these instructions.
The thermostat provides precise electronic control with large, easy-to-read display. Features up/down arrows for setpoint adjustment, SYSTEM switch (HEAT/OFF/COOL/AUTO), FAN switch (ON/AUTO), O/B for heat pumps. Display shows current temperature and setpoint. Supports single-stage heat/cool, heat-only, cool-only, and single-stage heat pumps.
Applications: Gas/Oil/Electric Heat: Yes; Heat Pump Single Stage: Yes; Heat Only: Yes; Cool Only: Yes; Millivolt: No; Hydronic: Yes.
CAUTION! To prevent electrical shock/equipment damage, disconnect power at main fuse/circuit breaker until installation complete. Label wires prior to disconnection.
WARNING! Do not use on circuits exceeding 30 VAC 50/60 Hz (1.5A max total); higher voltage damages control/causes shock/fire. Do not short terminals to test; incorrect wiring causes injury/property damage. Conform to NEC Class II circuits. Do not operate cooling below 50°F (compressor damage).
ATTENTION! This product does not contain mercury but may replace one that does. Dispose properly; refer to recycling resources.
A standard heat/cool thermostat consists of three basic parts: 1) Cover; 2) Base; 3) Subbase. Label each wire with terminal designation before disconnecting. Disconnect wires one at a time; do not let fall into wall.
Remove old thermostat. Mount new base level on wall, connect wires to terminals. For single transformer systems, install red jumper between RH and RC. Push excess wire into wall, secure base, attach thermostat body. Power up and configure.
Terminal Designations: RH/RC (power), W (heat), Y (cool/compressor), G (fan), O/B (changeover for heat pump).
Single Stage Heat/Cool: RH to hot, RC to hot (jumper RH-RC), W to heat relay, Y to compressor, G to fan.
Heat Only: Omit Y.
Cool Only: Omit W.
Heat Pump Single Stage: Y to compressor, O/B to changeover (O for cool, B for heat), W to aux if applicable.
CAUTION! RED jumper wire must be connected between RH and RC for single transformer systems.
Restore power. Set SYSTEM to HEAT/COOL, FAN to ON/AUTO, adjust setpoint to test.
CAUTION! Do not operate below 50°F.
Remove cover, press and hold UP and DOWN arrows simultaneously for 5 seconds to enter setup. Use UP/DOWN to adjust, press HOLD to advance.
| Setup # | Display | Options | Comments |
|---|---|---|---|
| 1 | 0 | -3 to +3 | Temperature Calibration |
| 2 | FA | SL | Cycle Rate (Fast/Slow) |
| 3 | 0 | 0-9 | Filter Timer Hours x10 |
| 4 | °F | °C | Temperature Scale |
| 5 | OFF | ON | Backlight |
| 6 | 0 | 1-4 | Auto Changeover Differential |
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Display Blank | Power loss. | Check transformer/wiring; restore power. |
| Heating/Cooling Not Working | Wrong mode, setpoint, wiring. | Set correct mode/setpoint; verify wires. |
| Fan Not Running | AUTO no call; wiring. | Set ON; check G terminal. |
| Short Cycling | Fast cycle setting. | Adjust to SL in setup. |
| Compressor Won't Start | 5-min lockout. | Wait; flashing COOL indicates lockout. |
| Filter Indicator On | Timer expired. | Change filter; reset timer in setup. |