Sensi ST75 Thermostat Operation Manual

The Sensi ST75 Touch Smart Thermostat is a Wi-Fi enabled touchscreen programmable thermostat for 24V HVAC systems. It offers smart control via the Sensi app, including scheduling, remote access, and energy savings. Compatible with single/multi-stage conventional systems, heat pumps, and more. Requires C-wire. Below are the key specifications and operation instructions.

Key Specifications

• Type: Wi-Fi enabled touchscreen programmable smart thermostat for 24V HVAC systems
• Compatibility:
  • Single/multi-stage conventional (gas/electric), heat pumps, boilers
  • Requires C-wire for power
  • Works with Sensi app on iOS/Android; compatible with Alexa, Google Assistant, Apple HomeKit
• Power Source:
  • 24 VAC from HVAC system via C-wire
• Electrical Rating:
  • 24V systems; max 1A per terminal
  • Terminals: RH/RC, C, G, Y/Y1, Y2, W/E, W2, O/B, L
• Temperature Range: 45°F to 99°F (7°C to 37°C); Humidity: 5% to 90% RH non-condensing
• Operating Conditions:
  • Indoor use only; 40°F to 120°F (4°C to 49°C)
  • Wi-Fi: 2.4GHz network required
• Dimensions: Compact wall-mount design with touchscreen display
• Features:
  • 7-day programming via app
  • Geofencing, energy reports, remote control
  • Touchscreen interface, back glow for installation
  • Circulating fan, humidification/dehumidification support
• Thermostat Configuration Options:
  • Models: ST75 series, 1F95U-42WF
  • UL listed; professional or DIY installation

Operation Instructions

Initial Setup

1. Download Sensi App: Install from App Store or Google Play; create account with email.
2. Power On: Install on wall after wiring (see Section 3); screen activates.
3. Configure System:

• Select model (ST75 series), system type (gas/electric/heat pump) in app.
• Connect to 2.4GHz Wi-Fi via app instructions.
• App guides through scheduling, location, and time zone setup.

Setting the Clock and Day

1. Syncs automatically via Wi-Fi connection.
2. Manual adjustment (Wi-Fi off): Menu > Time Setup; use arrows to set time/date.
3. Day auto-detected from app schedule and location.
4. Time zone set during app registration.

Operating in Non-Programmable Mode

1. Select Mode: Press Mode to cycle Heat, Cool, Off, Aux, Auto.
2. Adjust Temperature: Use up/down arrows.
3. Fan Control: Press Fan for Auto/On.
4. Manual Override: Turn Schedule Off for permanent hold; arrows for temp.

Operating in Programmable Mode

1. Factory Schedule: Default 7-day program via app.
2. Custom Schedule:

• Use Sensi app: Schedule tab to set times/temps.
• Manual (Wi-Fi off): Menu > Schedule; set 4 periods per day for weekdays/weekends.
• Enable geofencing for auto-adjust.

3. Temporary Override: Arrows for 2-hour hold minimum.
4. Permanent Hold: Turn Schedule Off.
5. Disable Programming: Schedule Off in app or on unit.

Advanced Features

1. Remote Control: Via Sensi app with Wi-Fi.
2. Energy Saving: Usage reports, geofencing, alerts.
3. Voice Control: Compatible with Alexa, Google Assistant, HomeKit.
4. HVAC Monitoring: System alerts via app.
5. Circulating Fan: Menu > Advanced Setup > Fan Mode Options; set 10%-100% runtime per hour.
6. Humidification/Dehumidification: Menu > Advanced Setup; set points if accessories installed.
7. Display Options: Menu > Home Screen Content for time/humidity/F/C.

Troubleshooting

• Blank/Flashing Display: Check C-wire connection; ensure 20-30VAC between RH/RC and C.
  
• No Heat/Cool: Verify mode, wiring; check HVAC/breaker; configure in Menu > Advanced Setup.
  
• Wi-Fi Issues: Ensure 2.4GHz, update app, reboot devices; check permissions.
  
• C-Wire Missing: Install C-wire or external transformer; see support site.
  
• Factory Reset: Menu > About Thermostat > Reset.

Installation Instructions

Warning: Turn off power at breaker before starting. DIY or professional installation. Requires C-wire for power.

Remove Old Thermostat

• Switch off power to HVAC at breaker.
• Remove old cover (screwdriver or latch).
• Photograph wiring for reference.
• Discard jumper wires (Sensi has built-in).
• Identify/label wires in app; select system type.
• Disconnect wires, remove base; secure wires.

Installing New Thermostat

1. Mount Base: Level and mark holes, secure with screws/anchors.
2. Connect labeled wires to terminals (push in securely).
3. Push excess wire into wall.
4. Attach touchscreen cover to base.
5. Turn on power; screen activates.
6. Menu > Wi-Fi to initiate connection; follow app for setup, naming, location registration.

Battery Location

• No user-replaceable batteries; powered by 24V C-wire.
• Back glow switch on base for installation lighting (turn off after).

Wiring and Configuration

Match wire labels to terminals. Clip RH/RC jumper if separate transformers. Access config: Menu > Advanced Setup.

System Type	Key Connections
Conventional Single Stage	RH/RC to RH/RC, C to C, G to G, Y to Y, W to W/E
Heat Pump Single Stage	RH/RC to RH/RC, C to C, G to G, Y to Y, O/B to O/B
Two-Stage Conventional	RH/RC to RH/RC, C to C, G to G, Y to Y, Y2 to Y2, W to W/E, W2 to W2
Dual Fuel Heat Pump	RH/RC to RH/RC, C to C, Y to Y, O/B to O/B, W to W2
Humidifier/Dehumidifier	Y2 or W2 for accessories

Caution: Ensure secure connections. Configure system type in app or Menu during setup. C-wire required.

Terminal Definitions:

• RH: Power for heating, 24V
• RC: Power for cooling, 24V
• C: Common wire, 24V
• G: Indoor blower (fan)
• Y: First stage cooling/heat pump
• Y2: Second stage cooling or humidifier
• W/E: First stage heat or aux/emergency
• W2: Second stage heat or dehumidifier
• O/B: Reversing valve for heat pump
• L: Heat pump system monitor

Menu Configurations Reference:

Menu Item	Default	Options
Sleep Mode	Off	On/Off
Backglow	Off	On/Off
Home Screen Content	On	Humidity/Time/°F/°C/Schedule
Wi-Fi	-	Connect/Off
Schedule	On	5/2 Day
Time Setup	-	Manual (Wi-Fi off)
Outdoor Setup	-	AC1/AC2/HP1/HP2/None
Indoor Setup	-	GA1/GA2/EL1/EL2/Fan
Reversing Valve	None	O/B/6/None
Circulating Fan	Off	10%-100% (5%)
Humidify	Off	5%-50% (5%)
Dehumidify	Off	40%-95% (5%)