This document is the installation guide for the TH4210D programmable thermostat. The thermostat is designed for electronic control of 24VAC heat pump systems with auxiliary heat. It must be installed by a trained and experienced technician. The document provides instructions and precautions for installation.
The guide provides safety warnings and preparation steps for installing the TH4210D programmable thermostat, including a pre‑installation checklist and required tools. It emphasizes disconnecting power before wiring to avoid electrical hazards.
Detailed instructions cover wall‑plate mounting, wiring diagrams, power options (24 VAC or AA batteries), and battery installation. The document also includes system settings, fan options, and troubleshooting references.
| Control type | Electronic control of 24 VAC heat pump systems with auxiliary heat (2 heat/1 cool) |
|---|---|
| Power options | Battery power or 24 VAC common wire (optional battery backup) |
| System settings | Heat, Off, Cool, Em Heat |
| Fan settings | Auto, On |
| Recommended wire gauge | 18‑ to 22‑gauge thermostat wire |
| Battery type | AA alkaline batteries (2) |
It can be powered by 24 VAC from the system transformer or by two AA alkaline batteries, with optional battery backup when AC power is used.
Use thermostat wire sized between 18 and 22 gauge.
Disconnect power before beginning any wiring to avoid electrical shock or equipment damage.