Overview
This guide explains how to wire a humidifier to a Nest thermostat, replacing a traditional humidistat setup for seamless control through the Nest interface.
Traditional Humidistat Setup
- Typical system includes a humidifier, humidistat, and HVAC wiring.
- Most humidifiers plug into a 120V outlet near the furnace to power the fan.
- The humidistat acts as a simple on/off switch, closing the circuit when humidity is low.
- Power flows from the R terminal through the humidistat and back to the C terminal, activating the humidifier.
- The humidistat’s two wires are connected to the R and C terminals inside the HVAC system.
Nest Thermostat Humidifier Wiring
- Nest thermostat requires only one wire connected to the star terminal for humidifier control.
- Select the star terminal’s function in the Nest settings after wiring.
- Connect a wire from the star terminal to the humidifier’s valve/relay; connect the other side to the C terminal.
- This creates a completed circuit: Nest sends a 24V signal down the star terminal when humidity is needed.
- Existing standard thermostat wires (R, G, Y, W1, C) remain as-is for other HVAC functions.
- If an R wire is already connected to your humidistat, move it to the star terminal; ensure the return path to C is established.
Testing and Troubleshooting
- After wiring, raise the Nest humidity setting to maximum; listen for the humidifier activating (click or fan noise).
- A multimeter can be used to confirm wire continuity if unsure.
- Follow the provided wiring diagrams for accurate conversion from the old setup.
Tips and Additional Resources
- Every humidifier may have slight wiring differences, but the circuit principle remains consistent.
- Visit the vendor’s website or related videos for more smart home wiring guidance and troubleshooting help.