This document provides instructions for installation and operation of Honeywell's CT8775A and CT8775C Digital Round thermostats. The thermostats are easy to use, have a large display, and feature backlighting.
The Digital Round™ thermostat by Honeywell offers a large, backlit display, no‑battery operation, and memory retention during power loss. It is designed for heat‑only (CT8775A) or heating‑cooling (CT8775C) applications using 20‑30 Vac power.
This Owner's Guide walks you through preparation, removal of the old thermostat, special installation scenarios, wiring, mounting of the decorator cover plate and wallplate, and final setup. It also includes compatibility charts, wiring diagrams, and troubleshooting tips.
| Power Supply | 20‑30 Vac |
|---|---|
| Battery Requirement | No batteries required |
| Backlit Display | On‑demand backlighting |
| Compatibility – Gas or Oil Warm Air | Yes |
| Compatibility – Electric Warm Air | No (heat‑only) / Yes (heat‑cool) |
Wrap the wires separately with electrical tape and keep them from touching to avoid damaging the transformer.
No, the CT8775A is not compatible with that application; only the CT8775C works.