Honeywell Home T4 Pro (TH4110U2005/U)
D0 No Radio — No radio at all. It cannot phone home.
The unplug test
Nothing changes, ever. There is no radio, no app, no account, and no server that has to be running for your heat to come on. You set the schedule with buttons on the wall the way you would set a microwave clock. It runs on two AA batteries or the C-wire, so it does not even need your Wi-Fi router to exist.
Why this tier: Manufacturer specification table states 'WiFi: No' and 'RedLINK: No', ruling out both the Wi-Fi and the proprietary 900 MHz radio, and Resideo holds no FCC grant for this model while holding grants for its connected thermostats.
Specifications
| Account required | none |
|---|---|
| Works offline | fully |
| Forced firmware updates | no |
| Radios | none |
| FCC ID | no intentional-radiator grant found |
| Local control | none |
| Phones home | none |
| Parts available | limited |
| Availability | in stock |
| Price band | $40-70 (seen 2026-09-02) |
| Vendor risk | 0 / 3 |
Where to buy
Sources
Class A is primary (manual, FCC filing, teardown). Class B is corroborated community reporting. Class C is never sufficient alone.
- A https://www.honeywellhome.com/products/t4-pro-programmable-thermostat
Manufacturer specification table states 'WiFi: No' and 'RedLINK: No'. Described as a standalone non-connected thermostat with push-button control, hardwired or battery operated, no app or cloud service. — accessed 2026-09-02 - A https://fccid.io/search.php?q=Resideo
Sibling control: Resideo holds thermostat radio grants for HS9-THX900WF01 (5855-5885 MHz) and HS9-THX1200WF01 (903-926.4 MHz), its connected models. No grant exists for the T4 Pro / TH4110U, so the absent grant is meaningful rather than an unfiled gap. — accessed 2026-09-02
History
- 2026-09-02 — First published at D0.
Last verified 2026-09-02 — 4 days ago.