Will it work with your system?
Works well with
- Phone control and scheduling
- Systems the maker's checker confirms
Check first if you have
- Line-voltage baseboard heat
- Millivolt gas heaters
What it controls
The Sensi ST55 Smart Thermostat is a smart Wi-Fi thermostat. Systems, per the maker: Works with HVAC equipment found in most homes.
Check your wall for a C terminal: its maker says no C wire is needed ("Common wire (c-wire) is not required in most applications"). The C wire guide covers adapters.
The listing doesn't state heat pump support; if you have an O/B wire, confirm with the maker before ordering. Heat pump wiring.
Connectivity: Wi-Fi. It amazon Alexa, Apple HomeKit, Google Assistant, SmartThings, Vera.
Not sure of your wiring? The wiring checker reads your system from the terminal letters and checks it against this model's statements.
Also on the listing: dimensions of 1 in (D) x 5.88 in (W) x 3.75 in (H), a weight of 11.68 ounces and a led.
Warranty, per the listing: 3 years.
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 | ST55 | Retailer |
|---|---|---|
| Model name | ST55 | Retailer |
| Dimensions (seller) | 1"D x 5.88"W x 3.75"H | Retailer |
| Works with | Amazon Alexa, Apple HomeKit, Google Assistant, SmartThings, Vera | Retailer |
| Features (seller) | Data Privacy, Easy DIY Install, Energy Savings, Filter Indicator, Programmable | Retailer |
| Connectivity | Wi-Fi | Retailer |
| Power | Corded Electric | Retailer |
| Voltage | 24 V AC | Retailer |
| Display | LED | Retailer |
| Mounting / installation | Wall Mount | Retailer |
| Batteries | 2 AA batteries required. (included) | Retailer |
| Material | Plastic | Retailer |
| Warranty | 3 years. | Retailer |
| Product weight | 11.68 ounces | Retailer |
| C-wire | Common wire (c-wire) is not required in most applications | Retailer |
| Works with systems | Works with HVAC equipment found in most homes | Retailer |
Strong points and weak points
Strong points
- No C wire needed (maker)
- Works with Amazon Alexa, Apple HomeKit, G
Weak points
- 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 Sensi ST55 Smart Thermostat need a C wire?
Does the Sensi ST55 Smart Thermostat work with a heat pump?
Other smart thermostats with similar wiring
- Honeywell Home RTH6580WF Smart Thermostat
- Vine TJ-560-3 Smart Thermostat
- Sensi ST75 Smart Thermostat
- Sensi 1F87U-42WF Smart Thermostat
All smart thermostats in one grid · Every Sensi control listed
Our take
Suited to 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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