The White Rodgers 7904 is a 5+2 day programmable electronic digital thermostat for low voltage heating and cooling systems, compatible with standard heat/cool or heat only systems, electric heat, gas or oil fired systems, hydronic (hot water or steam) systems, single-stage heat pump systems, and millivolt systems. It features separate 5-day (weekday) and 2-day (weekend) programming with four time/temperature settings per 24-hour period, simultaneous heat/cool programs, preprogrammed temperature control, and battery backup with 3 AA Energizer batteries. Powered by 8-30 VAC; compatible with systems up to 1.5A per terminal, 1.5A max total. Below are the key specifications, installation, operation, programming, and troubleshooting instructions.
Assemble tools: hand or power drill with 3/16 inch drill bit (if needed), flat blade screwdriver, wire cutter/stripper. Shut off electricity at main fuse box until installation complete. Label wires before disconnecting. This thermostat is for low voltage systems only; not for line voltage. Install away from drafts, direct sunlight, or heat sources for accurate sensing. Install 3 AA Energizer alkaline batteries before programming.
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 uses solid-state microcomputer technology to provide precise time/temperature control. Features 5+2 day programming with four time/temperature settings per day, simultaneous heat/cool programs, automatic changeover (selectable), compressor protection, fan auto/on, LCD continuously displays set point and alternates time and room temperature, temperature override until next program period, manual program override (HOLD temperature), user selectable 12/24-hour clock, °F/°C convertibility. Terminals: R (hot), C (common), G (fan), Y (compressor), W (heat), O/B (changeover).
Applications:
| System Type | Supported |
|---|---|
| Standard Heat/Cool or Heat Only Systems | Yes |
| Electric Heat Systems | Yes |
| Gas or Oil Fired Systems | Yes |
| Gas Systems with Intermittent Ignition Devices (I.I.D.) and/or Vent Dampers | Yes |
| Hydronic (Hot Water or Steam) Systems | Yes |
| Single-Stage Heat Pump Systems | Yes |
| Millivolt Systems | Yes |
| Multi-Stage Systems | No |
| Systems Exceeding 30 VAC and 1.5 Amps | No |
| 3-Wire Zoned Hydronic Heating Systems | No |
CAUTION! To prevent electrical shock/equipment damage, disconnect power at main fuse/circuit breaker until installation complete. Label wires prior to disconnection. If in doubt about wiring, consult qualified heating/air conditioning contractor.
WARNING! Do not use on circuits exceeding 8-30 VAC 50/60 Hz (0.05-1.5A per terminal, 1.5A max total); higher voltage damages control/causes shock/fire. Do not short terminals on gas valve/primary control to test; short/incorrect wiring burns out components/causes injury/property damage. Conform to NEC Class II circuits. Do not operate cooling below 50°F (compressor damage).
ATTENTION! Handle the control carefully to avoid malfunction. Rough handling or distorting components could cause the control to malfunction. This product does not contain mercury but may replace one that does. Do not open mercury cells; if damaged, wear non-absorbent gloves, clean up spilled mercury, place in sealed container. Refer to www.thermostat-recycle.org for disposal.
A standard heat/cool thermostat consists of three basic parts: 1) Cover; 2) Base; 3) Subbase. Shut off electricity at main fuse box. Remove the front cover of the old thermostat. With wires still attached, remove the wall plate from the wall. If the old thermostat has a wall mounting plate, remove the thermostat and wall mounting plate as an assembly. Loosen screws and remove wires one at a time, labeling each. Note heat anticipator setting (.2, .4, .8, etc.) for reference.
Set option switches and program thermostat with batteries installed before attaching to subbase. Mount subbase to wall/adaptor plate with mounting screws. Connect wires to corresponding terminals. Reattach base to subbase and install cover. Keep area clear of wires.
Batteries: Install 3 AA Energizer alkaline; low battery flashes "BATTERY".
Terminal Designations: R (hot), C (common), G (fan), Y (compressor), W (heat), O/B (changeover).
Heating System (2-Wire, Single Transformer or Millivolt): Add jumper wire between R and B terminals on the primary control (jumper wire not provided with thermostat).
Cooling System (2-Wire, Single Transformer): Add jumper wire between R and B terminals on the primary control (jumper wire not provided with thermostat).
Heat/Cool System (Single Transformer): Add jumper wire between R and B terminals on the primary control (jumper wire not provided with thermostat).
Heat Pump System (Single Stage): Typical wiring for single stage heat pump systems.
CAUTION! All wiring must conform to local and national electrical codes and ordinances. Refer to equipment manuals for specifics.
Turn on power to the system. Move SYSTEM switch to HEAT or COOL position. Press FAN button to ON. If system does not operate properly, contact qualified serviceperson.
For heat pumps: If the thermostat loses power, the system will switch to emergency heat.
CAUTION! Do not operate below 50°F.
5+2 day programming with four time/temperature settings per 24-hour period. Separate 5-day (weekday) and 2-day (weekend) programming. Choose start times, heating temperatures, and cooling temperatures independently for both weekday and weekend programs. Factory preprogrammed.
User may select either 12- or 24-hour clock display and °F/°C convertibility. Factory settings: Preprogrammed temperature control; default temperature range 45°F to 90°F.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Screen is not lighting up | Low batteries. | Replace batteries with fresh “AA” Energizer® alkaline batteries. Check for incorrect or missing wiring, such as a missing jumper wire between RH and RC terminals. |