Will it work with your system?
Works well with
- Phone control and scheduling
- Heat pump systems
Check first if you have
- Line-voltage baseboard heat
- Millivolt gas heaters
What it controls
The Resideo S900 Smart Thermostat is a smart Wi-Fi thermostat. Systems, per the maker: Works with dual fuel, fan-coil, PTAC, and radiant systems.
On power, the listing doesn't say whether it needs a C wire. What a C wire does.
The maker states heat pump support ("Up to 3H/2C heat pump or 2H/2C conventional"), so it can drive an O/B reversing valve. What a heat pump needs from a thermostat.
Stages, per the maker: 3H/2C heat pump. Compare that with the W2 and Y2 wires at your wall. Reading stages from your wires.
Connectivity: Wi-Fi. It touchscreen.
Tick your terminals in the wiring checker to see whether its maker's statements cover your system.
Also on the listing: a touchscreen.
Compatibility and specs
These come from the maker's listing for this exact model; the source of each is marked. Anything the maker leaves out is marked not stated.
| Model number | S900 | Retailer |
|---|---|---|
| Works with | Touchscreen | Retailer |
| Features (seller) | Programmable | Retailer |
| Connectivity | Wi-Fi | Retailer |
| Display | touchscreen | Retailer |
| Works with systems | Works with dual fuel, fan-coil, PTAC, and radiant systems | Retailer |
| Heat / cool stages | 3H/2C heat pump | Retailer |
| Heat pump support | Up to 3H/2C heat pump or 2H/2C conventional | Retailer |
Strong points and weak points
Strong points
- Heat pump support stated
- Stages: 3H/2C heat pump
- Works with Touchscreen
Weak points
- C-wire need not stated
- Needs Wi-Fi for smart features
Wiring and install notes
- Compatibility statements are the maker's own. Confirm with the maker's compatibility checker, turn the power off before wiring, and leave line-voltage and furnace work to a licensed electrician or HVAC technician.
Thermostats to compare it with
FAQ
Does the Resideo S900 Smart Thermostat need a C wire?
Does the Resideo S900 Smart Thermostat work with a heat pump?
Other smart thermostats with similar wiring
Our take
Shortlist it for phone control and scheduling.
Where to get it
The link goes to this exact model's listing. Check that the box includes the trim plate or C-wire adapter you need, and confirm your wiring with the maker's compatibility checker before you order.
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