Smart thermostat guide
Sensi Touch Smart Thermostat ST75 (Black)
24 VAC systems with a C wire, including 2-stage and heat pump set-ups, where humidity control matters
The Sensi Touch colour touchscreen thermostat, confirmed by matching UPC. It needs a C wire and a 2.4 GHz network, and the guide requires the Sensi app for setup and advanced features. Copeland lists 2H/2C conventional and 4H/2C heat pump staging, humidifier and dehumidifier control, and a 3-year warranty.
Listing checked . Confirm the model, included parts and availability before ordering.
Published specifications
- Maker: stages 1H/1C, 2H/2C conventional, 4H/2C heat pump; dual fuel
- Maker and listing: C wire required; 20-30 VAC; no line voltage or millivolt
- Guide: Sensi app and account for setup and remote features; Wi-Fi 2.4 GHz
- Maker: humidification and dehumidification control; set-point 45-99°F
- Maker: 5.65 x 3.40 x 1.00 in; 4.3-inch touchscreen; up to 8 periods a day
- Maker and listing: 3-year warranty
Fit and limits
Strengths
- UPC matches Copeland's page, which publishes a full spec block
- Maker lists humidifier and dehumidifier control plus 4H/2C heat pump staging
- Three-year warranty listed by maker and listing
Caveats
- C wire required on every compatible system type
- Scheduling and advanced settings need the Sensi app and an account
- Listing's AA-battery field and dimensions differ from Copeland's specs
What the ST75 is and how it is identified
The ST75 is the Sensi Touch, a Wi-Fi thermostat with a 4.3-inch colour LCD touchscreen, listed on Copeland's Sensi site. Copeland's product page lists SKU and model number ST75 with UPC 786710554841, the same UPC as the Amazon listing. Both Sensi guides supplied with the listing name the ST75 series on their covers.
Copeland lists the box contents as the thermostat, instructions, mounting hardware, wire labels and warranty. Copeland gives the size as 5.65 by 3.40 by 1.00 inches; the Amazon listing shows 5.63 by 3.2 by 1.17 inches. The two sets of figures differ slightly, and neither source explains the difference.
C wire: required, and the listing's battery field
Copeland's page and the listing both say a common wire, or C wire, is required, and Copeland lists the power source as hardwire. A 20-page pro installation booklet supplied with the listing, which does not name the model on the pages we read, has a compatibility table that marks conventional, heat-only, cool-only and heat pump systems as compatible but requiring a C wire. It lists communicating proprietary systems, line voltage and millivolt systems as not compatible.
The installation guide explains that a battery-powered light in the base is only for seeing the wiring during installation, lasts about an hour, and is not a sign that the thermostat has power. The Amazon details table says AA batteries are required, while Copeland lists batteries included as no and power as hardwire. The guide points heat-only system owners to an external transformer option on Sensi's support site.
Stages and systems
Copeland lists stages as single stage 1H/1C, multi-stage 2H/2C and heat pump 4H/2C, with applications including 3-wire zone heat, conventional air conditioning, gas, oil and electric heat, and heat pumps. It also lists dual fuel control through logic control, an electrical rating of 20 to 30 VAC, and terminals RC, RH, C, W/E, W2, Y, Y2, O/B, G and L.
The manual operation guide's equipment menu offers outdoor settings of AC1, AC2, HP1, HP2 or none, and indoor settings of GA1, GA2, EL1, EL2 or fan. Mode choices on the thermostat are heat, cool, off, aux and auto. We do not reproduce wiring steps here; the installation guide supplied with the listing has them.
Humidity control and the circulating fan
Copeland lists humidity control as humidification and dehumidification. The manual operation guide shows humidifier and dehumidifier settings for equipment wired to the thermostat, with humidification adjustable from 5 to 50 percent and dehumidification from 40 to 95 percent, and recommends humidification setup for a contractor only.
The circulating fan can be set to run a percentage of each hour, from 10 to 100 percent in 5 percent steps; the guide's example is 50 percent meaning 30 minutes an hour, with heating or cooling runtime subtracted. Copeland lists a set-point range of 45°F to 99°F and service reminders for filters, humidifier pads and UV bulbs.
App, account, Wi-Fi and what works at the wall
The installation guide says you must use the Sensi app to install and configure the thermostat correctly, and that creating an account with an email address is required for remote access and full features. It tells you to use a 2.4 GHz network, and Copeland's specifications list Wi-Fi 2.4 GHz and Bluetooth Low Energy.
The manual operation guide says the thermostat can be run at the wall, but advanced features such as settings, scheduling and email alerts are only available through the app. Without Wi-Fi, it allows a basic four-point schedule set at the unit for weekdays and weekends; Copeland lists up to eight program periods a day with the app. A temporary change holds until the next set point, for at least two hours.
Privacy and warranty
The listing and Copeland's page both state that Sensi will not sell your personal information to third parties. Copeland lists Amazon Alexa, Google Assistant and Samsung SmartThings among compatible platforms, and its features text also names Apple HomeKit.
Copeland lists the warranty period as 3 years, and the Amazon warranty field also says 3 years. We did not read Copeland's full written warranty terms, so check them before relying on the three-year term.
Check the current listing
Confirm the model, included parts and availability before ordering.
Primary sources
- Copeland product page and specifications for Sensi Touch Smart Thermostat ST75
- Sensi Touch Smart Thermostat installation guide R-5021 (listing-supplied PDF)
- Sensi Touch Smart Thermostat manual operation guide R-5030 (listing-supplied PDF)
Primary sources checked .
Compare with
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Conventional or heat pump systems up to two stages, on a 2.4GHz network, in the old thermostat's footprint
- Google Nest Thermostat (Charcoal)
Single-stage 24V systems that need a schedule and app control, not multi-stage equipment
- Mysa Smart Thermostat V2 for Electric Baseboard Heaters (BB.2.0.01.NA-US)
120V or 240V electric baseboard, fan-forced convector and radiant ceiling heat in a standard gang box
- ecobee Smart Thermostat Premium with SmartSensor
24 VAC forced-air, heat pump, boiler or PTAC systems, checked first with ecobee's compatibility tool
- Google Nest Learning Thermostat (4th gen) with Nest Temperature Sensor (2nd gen)
Multi-stage 24V systems run through the Google Home app, in homes with or without a C wire
- ecobee Smart Thermostat Essential (EB-STATE7-01)
Simple single-transformer systems with one stage of cooling, on a 2.4GHz network