Sensi™ Smart Thermostat Humidity Control Guide
Models: 1F87U-42WF, ST55, NH-AWIFI, OH-AWIFI
Version: April 2023
Emerson Electric Co. All rights reserved R-5622
1. Contractor Firmware Update Process
Connect the thermostat to Wi-Fi and register it to the customer's account to ensure the thermostat has the latest firmware release.
2. Installation - Compatibility and Wiring
| SENSI THERMOSTAT | CONVENTIONAL SYSTEM CONNECTION | HEAT PUMP SYSTEM CONNECTION |
|---|---|---|
| RC | Power for cooling, 24V | Power for cooling, 24V |
| RH | Power for heating, 24V | Power for heating, 24V |
| C | Common wire, 24V | Common wire, 24V |
| Y | 1st stage cool | 1st stage heat and cool (compressor) |
| Y2/* | 2nd stage cool (or humidifier) | 2nd stage heat and cool (or humidifier) |
| W/E | 1st stage heat | 1st stage auxiliary/emergency heat (2nd stage heat) |
| W2/* | 2nd stage heat (or dehumidifier) | 2nd stage auxiliary/emergency heat (3rd stage heat or dehumidifier) |
| G | Indoor blower (fan) | Indoor blower (fan) |
| O/B | Heat pump changeover, zone panel or 3-wire hot water zone valve connection. (configurable as O, B or 2 in the installer menu) | Heat pump changeover (reversing valve) connection (configure as O or B in the installer menu) |
| L | no function | "L" terminal connection |
1-Wire Humidification & Dehumidification
Thermostat Wiring for Humidifier/Dehumidifier
This diagram illustrates the wiring connections for a Sensi thermostat to control humidification and dehumidification. It shows the thermostat terminals (RC, RH, O/B, Y, G, W/E, C, L, Y2/*, W2/*) connected to a system transformer (LINE VOLTAGE, COMMON) and a furnace/air handler terminal strip (R, C, W, Y, G, DHUM). A 24V humidifier is connected to the furnace/air handler strip. Key notes indicate that the W2/* terminal de-energizes on a call for dehumidification when cooling is active, and the Y2/* terminal energizes on a call for humidification when heating is active.
Dehumidification with Relay Installed
This diagram details the setup for dehumidification using a relay. The thermostat terminals (RC, Y, G, W2/*) are connected to the furnace/air handler terminal strip (R, Y, G, C, DHUM). A relay (e.g., 90-293Q) is wired to the DHUM terminal and controls the dehumidifier. The diagram specifies fan output modes: 'NORMAL COOL SPEED POSITION' when DHUM is energized, and 'DEHUM SPEED MODE' when DHUM is de-energized.
3. Configuration – Setting Humidification/Dehumidification Control Capability On/Off
| Display Code | Menu item | Default | Options |
|---|---|---|---|
| Wireless setup Connects thermostat to wi-fi network | -- | Connect | |
| F | Fahrenheit or celsius | F | F C |
| AC2 | Outdoor equipment configuration Cooling or heat pumps | AC2 | AC1 – Conventional cooling 1 (single-stage) AC2- Conventional cooling 2 (two-stage) HP1 - Heat pump 1 (single-stage) HP2 - Heat pump 2 (two-stage) ACO - No cooling |
| EL2 | Indoor equipment configuration For gas or electric heat | EL2 | EL1- Electric 1 (single-stage) EL2- Electric 2 (two-stage) FAn GA1 – Gas 1 (single-stage) GA2 – Gas 2 (two-stage) |
| O | Reversing valve position Selects “O” or “B” setting For heat pumps only | O | O B 2 |
| Fn | Circulating fan | OFF | Off/10% - 100% (5% increments) |
| H AA | Humidification Add accessory | OFF | Off/On |
| H SP | Humidification Set point | OFF | Off/5% - 50% (5% increments) |
| dH AA | Dehumidification Add accessory | Od | Od/Oc Od - Optimal dehumidification (overcool to dehumidify) Oc - Optimal comfort (wired dehumidification) |
| dH SP | Dehumidification Set point | OFF | Off/40% - 95% (5% increments) |
| Wireless radio Turns wi-fi radio on/off | ON | Off/On |
Humidification Control at the Thermostat
Ensure HVAC settings are single stage
To set up a wired humidifier accessory on this model, ensure the HVAC settings are configured for single stage first (single stage cooling for humidifier, or single stage heating for dehumidifier). Humidity control options will not appear in the menu if the thermostat is configured for multi-stage.
Setting up wired humidification
With the thermostat displaying the room temperature:
- Press [Menu].
- Press [Next] 7 times.
- Use the [Up Arrow] button to toggle Humidity On.
- Press [Next].
- Use the [Up Arrow] button to change the set percentage (SP) to your desired percentage to maintain.
- Press [Exit].
Setting up wired dehumidification
With the thermostat displaying the room temperature:
- Press [Menu].
- Press [Next] 8 times. (This may vary based on other settings; look for the "dH AA" menu.)
- Use the [Up Arrow] button to toggle Dehumidity "On."
- Press [Next].
- Use the [Up Arrow] button to change the set percentage (SP) to your desired percentage to maintain.
- Press [Exit].
Humidification Control in the Sensi App
Adjusting humidity features from the Sensi app
After initially enabling the feature on the thermostat, you can edit it via the Sensi app.
- Open the Sensi app.
- Tap your Thermostat Name.
- Tap the Settings Gear icon.
- Tap System Settings.
- Scroll to the Humidity Control section.
Here, you can toggle humidification features on/off and adjust the set percentage. If wired dehumidification is not configured, an alternative option will be available that uses the cooling system to remove moisture by overcooling the space up to 3 degrees.
Frequently Asked Questions
| FAQ | ANSWER |
|---|---|
| When can I get the firmware OTA update for humidity control? | OTA updates are pushed via Wi-Fi after being registered to the customer's account on the Sensi app. |
| Which versions of Sensi thermostats are compatible with humidity control? | Sensi Touch (1F95U) and Sensi (1F87U) smart thermostats are all backward compatible. 1F86U and UP500W models are currently not compatible. |
| What terminals should I use to enable humidity control? | Use Y2/* for humidification and W2/* for dehumidification. |
| What types of humidifiers and dehumidifiers are supported? | Humidifiers: Any 24VAC humidifier. Currently, Sensi does not support independent (call for heat) humidification. Dehumidifiers: HVAC systems with dehumidify mode (slowing of the system's fan speed) or 24VAC dehumidifiers. Currently Sensi does not support independent (call for cool) dehumidification. |
| What is an appropriate humidity setpoint? | Depending on the outdoor temperature, the ideal indoor humidity level is between 30-50% RH. In cold weather, if condensation appears on your windows, lower the humidity setpoint. |
| What is overcooling to dehumidify? | On air conditioning systems without a dehumidifier, the dehumidification feature allows Sensi to overcool to a maximum of 3º below the AC setpoint to help control the humidity. Overcooling is an option to dehumidify without having to wire additional accessories. |
| Why is my system unable to reach my humidity setpoint? | During extremely cold and dry or hot and humid climates, your humidifier or dehumidifier may not be able to increase or decrease humidity enough to reach your setpoint depending on the size of your equipment. |
