APOLLO Wi-Fi Fan Coil Thermostat

A fan coil thermostat controls a fan coil unit (FCU) — a hydronic air handler that uses hot or chilled water to heat and cool a room. Unlike a standard residential thermostat that simply signals a furnace or AC on or off, an FCU thermostat must control multiple fan speeds (low, medium, and high) and switch heating and cooling valves independently. It also needs to operate at the low voltages common in FCU wiring (12–24VAC/DC), rather than the line voltage used by electric baseboard heaters. The APOLLO Wi-Fi Fan Coil Thermostat is purpose-built for this: it handles 2/4-speed fan coil unit control, supports both 2-pipe and 4-pipe hydronic configurations, and adds Wi-Fi remote access and scheduling on top.

Yes. The APOLLO Wi-Fi thermostat supports both 2-pipe and 4-pipe fan coil unit configurations. In a 2-pipe system — the most common setup in residential and condo buildings — the same supply and return lines alternate between hot and chilled water depending on the season, and the thermostat switches between heating and cooling modes accordingly. In a 4-pipe system, separate heating and cooling coils run simultaneously, allowing the thermostat to call for heating or cooling independently at any time of year. Both configurations are supported under the same wiring terminal block.

Yes. The APOLLO Wi-Fi thermostat is rated for 2/4 fan coil unit control, covering fan coil units with two, three, or four fan speed outputs. The thermostat selects fan speed automatically based on how far the room temperature is from the setpoint — running low speed for light conditioning and stepping up to medium or high when the space needs to recover faster. This tiered fan control reduces noise during normal operation and only calls for maximum airflow when needed.

The APOLLO Wi-Fi Fan Coil Thermostat accepts both low-voltage and line-voltage power: 12–24VAC/DC (the standard in most commercial and residential hydronic fan coil installations) and 110–240VAC for locations where only line voltage is available at the thermostat. This dual-voltage design means you can install it with your existing wiring in most cases — no additional transformer or rewiring is required. Relay contacts are rated at 5A maximum per relay (SPST-NO), which covers the control outputs for fan speed and valve switching on virtually all standard fan coil units.

The APOLLO thermostat connects to your 2.4GHz home or building network using IEEE 802.11 b/g/n with WPA/WPA2 security. Once connected, the companion app lets you adjust the setpoint, switch between heating and cooling modes, change fan speed, view the current room temperature and humidity, and update 7-day schedules — all from your phone. GEO-fence mode uses your smartphone's location to automatically set back the temperature when you leave and restore comfort before you return. The thermostat also supports Modbus RTU and Modbus TCP for integration into building management systems, and Google Home for voice-based monitoring.

In most cases, yes. The APOLLO thermostat uses an industry-standard FCU terminal block layout compatible with the same wiring conventions used by Honeywell TB6575, TB8575 SuitePro, PECO, Johnson Controls, Siemens, and other major fan coil thermostats. Label and photograph your existing wiring before removal, then match the terminals on the APOLLO. The product manual — available for download on this page — includes a full wiring diagram covering 2-pipe and 4-pipe configurations. For fan coil units using Modbus control rather than direct relay switching, the APOLLO also supports Modbus RTU over RS-485.

No. Nest, Ecobee, and similar mainstream smart thermostats are designed for single-speed forced-air systems (gas furnaces and central air conditioners) and do not natively support multi-speed FCU fan control, 2-pipe or 4-pipe valve logic, or the low-voltage wiring conventions used by fan coil units. Installing a standard smart thermostat on an FCU typically results in only one fan speed working or incorrect heating and cooling behavior. Honeywell's TB6575 and TB8575 SuitePro models are among the few conventional alternatives built specifically for fan coil units, but they lack Wi-Fi and remote app access. The APOLLO Wi-Fi Fan Coil Thermostat is purpose-built for FCUs and adds the smart connectivity those models cannot provide.

The APOLLO thermostat platform covers several hydronic and electric heating applications. In addition to the Fan Coil Unit thermostat on this page, the same hardware family includes dedicated models for radiant floor heating, boiler control, pool and spa aquastat (water temperature control), snow melt systems, and electric baseboard or forced-air heaters. Each model is pre-configured for its specific application — select the right model from the dropdown at the top of this page. If you are building a multi-zone system with an air-to-water heat pump driving both fan coil units and radiant floor circuits, different APOLLO models can be used for each zone type within the same installation.

A programmable fan coil thermostat stores a fixed weekly schedule — typically 5-2 day or 7-day — and runs without any external connection. It is reliable and simple, but adjusting the schedule requires physical access to the thermostat. A smart Wi-Fi thermostat like the APOLLO adds remote app control so you can change setpoints or schedules from anywhere, GEO-fence automation that adjusts temperature based on your phone's location, and Modbus connectivity for building management system integration. For most residential and light-commercial fan coil installations, the smart Wi-Fi model delivers noticeably better comfort and energy management without adding installation complexity.

Yes. The thermostat supports 7-day scheduling with independent time-and-temperature programs for each day of the week. GEO-fence mode uses your smartphone's location to automatically switch to an energy-saving setback when you leave home and restore your comfort temperature before you return. Auto-detect mode uses the built-in ambient light and humidity sensors to adjust operation based on actual room conditions. All automation features are configured through the companion app and can be updated remotely without being at the thermostat.