Emerson Sensi ST75 User manual

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PRO Installation
Touch Wi-Fi
Thermostat

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Designed by the pros for the pros
There are a lot of choices when it comes to buying a thermostat,
but only one combines 125 years of experience and the latest
connected home technology to empower your customers
to take control of their comfort from anywhere. We proudly
connect you to a professional-grade thermostat that you
can offer your customers with confidence and that will keep
you connected with them even after the initial install.
Sensi partner program
Always be the Contractor-On-Call with your customers.
The Sensi app saves your contact information so when your
customer needs service, you’re just a tap away. Register at
www.sensiregistration.com.
Need help?
Visit sensicomfort.com/support for around-the-clock
access to support articles, instructional downloads
and comprehensive support videos. Our highly-trained
Sensi Support Team is available seven days a week.
1.888.605.7131
[e-mail]

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Easy to install and connect
Sensi is designed to install like a standard thermostat. It
gives you the flexibility to connect to Wi-Fi at installation
or let your customer connect it later using the Sensi app.
MOBILE DEVICE COMPATIBILITY
OPERATING SYSTEM COMPATIBILITY
iOS Yes
Android Yes
Amazon Fire Yes
SMART HOME PLATFORM COMPATIBILITY
OPERATING SYSTEM COMPATIBILITY
Wink Yes
Amazon Alexa Yes
Apple HomeKit Yes

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HVAC SYSTEM COMPATIBILITY
SYSTEM TYPE COMPATIBILITY MODIFICATIONS
Conventional heating and
cooling
•Gas furnace
•Air conditioner
•Electric furnace
•Boiler
Yes Requires a common
wire (c-wire)
Heat only
•Gas furnace
•Electric furnace
•Boiler
Yes Requires a common
wire (c-wire)
Cool only
•Air conditioner Yes Requires a common wire (c-wire)
Heat pump Yes Requires a common
wire (c-wire)
Communicating
proprietary systems No Needs standard HVAC wiring
Line voltage No Requires low voltage
(20-30VAC)
Millivolt systems No Requires 20-30VAC

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What’s in the box?
•Sensi Thermostat
•Screws and Anchors
•Wire Labels
•Sensi Security Code
(found on the back of the Welcome Guide)
Items needed for Wi-Fi connection:
•The homeowners compatible iOS or Android
•Device with the Sensi app installed and registered
•Your customer’s Wi-Fi network name (SSID) and password
QUICK TIP: Ask the homeowner to download the
Sensi app and gather their Wi-Fi information
while you are installing the thermostat.

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Installation
1. Install Sensi thermostat, referring to these terminal
definitions, cross references and wiring diagrams as needed:
OLD
THERMOSTAT
SENSI
THERMOSTAT
CONVENTIONAL
SYSTEM
HEAT PUMP
SYSTEM
RH RH* Power for heating, 24V
RC, R RC* Power for cooling, 24V
C, X, B** C Common wire, 24V
Y, Y1 Y 1st stage cool 1st outdoor
stage heat
Y2 Y2/* 2nd stage cool 2nd outdoor stage
heat and cool
W, W1, W/E,
Aux/E, E W/E 1st indoor stage heat 1st stage axillary/ emergency heat
W2*** W2 2nd indoor
stage heat 2nd stage axillary/ emergency heat
G G Indoor blower (fan)
O,B,** O/B O/B Changeover (reversing valve) connection
for heat pump or zone panel systems
L L no function “L” terminal
connection
* Two transformer systems (separate RC and RH wires), clip jumper located
on backplate to the right of the terminals.
** Label “B” as “C” only if the old thermostat also had a wire in “O”. If there is no wire
on “O”-label the wire “B”.
*** On Heat Pump system with separate W2 and E wires, label both wires W/E
(2 wires in one terminal).

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SINGLE STAGE OR MULTI-STAGE SYSTEM NO HEAT PUMP) WITH TWO TRANSFORMERS
System Configuration
Thermostat
*
*Two transformers systems (separate RC and RH wires), clip internal RC/RH jumper, located on back of thermostat.
HOT
120 VAC
NEUTRAL
HOT 120 VAC NEUTRAL
NEUTRAL 24 VAC HOT
NEUTRAL
24 VAC
HOT
Cooling Transformer
Heating Transformer
Dots Indicate
Phased
Relationship
Dots Indicate
Phased
Relationship
Single
Stage
AC1
GA1
EL1
24 Volt
(Hot)
Cool
24 Volt
(Hot)
Heat
24 Volt
(Common)
Cool
Mode
1st stage
Blower Circulator Fan Energized On Call For Cool (And Heat If Confi- gured For Electric Heat)
O
Energized
Constantly
in Cool
Mode
(Factory
Default)
B
Energized
Constantly
In Heat
Mode (Or
Aux Mode)
Heat
Mode
1st Stage
Heat
Pump “L”
Terminal
Connection
Cool
Mode
2nd Stage
No
Output
Heat
Mode
2nd Stage
No
Output
Multi-
Stage
AC2
GA2
EL2

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HEAT PUMP SYSTEMS
System Configuration
Thermostat
*
**
*Internal jumper between RC and RH, located on back of thermostat.
**Common connection required on Heat-only, Cool-only or Heat Pump systems.
HOT 120 VAC NEUTRAL
NEUTRAL
24 VAC
HOT
Dots Indicate
Phased
Relationship
Single
Stage
Heat
Pump
HP1 24 Volt
(Hot)
Cool
24 Volt
(Hot)
Heat
24 Volt
(Common)
Heat And
Cool Mode
1st Stage
(Com-
pressor)
NOTE: Dual
Fuel Option
De-Energizes
Heat Mode
1st Stage
Blower/ Circulator Fan Energized On Call For Cool (And Heat If Configured For Electric Heat)
O
Energized
Constantly
in Cool
Mode
(Factory
Default)
B
Energized
Constantly
In Heat
Mode (Or
Aux Mode)
Heat
Mode
1st Stage
Heat
Pump “L”
Terminal
Connection
Cool
Mode
2nd Stage
No
Output
Heat
Mode
2nd Stage
No
Output
Multi-
Stage
Heat
Pump
HP2

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2. After installation, configure the thermostat to the
appropriate system type. Press “Menu” on the thermostat
and refer to these menu options as needed:
CONFIGURATION MENU ITEMS REFERENCE
No. Menu item Default Options
1Screen Brightness Off Adjust resting state brightness
with an option to turn off
2Nightlight Off Off / On
3Home Screen Content On
On
°F
Indoor Humidity
Time of Day
°F / °C
4Schedule - 5 / 2 Day Schedule
5Wi-Fi O Connect to Wi-Fi
6 Time Setup - Set the date and time
7About Thermostat Model Number / Reset
8Setup HVAC AC2 / EL2
AC2
EL2
O
Outdoor Setup AC1/
AC2/HP1/HP2/AC0
Indoor Setup GA1/
GA2/EL1/EL2/Fan
Reversing Valve Position O/B/3

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3. Once the thermostat is installed and properly configured,
test the equipment by following these steps:
• Turn on power to the system.
• Fan Operation
•If your system does not have a “G” terminal
connection, skip to “Heating System” below.
•Press the “Fan” button on the thermostat and select the
“On” position. The blower should begin to operate.
•Press the “Mode” button to turn off the system. Then
press the “Fan” button on the thermostat and select the
“Auto” position. The blower should stop immediately.