Honeywell Home T4 Pro programmable thermostats (TH4110U2005, TH4210U2002): quick sheet

Covers: T4 Pro series: TH4110U2005 (1H/1C conventional or 1H/1C heat pump without aux) and TH4210U2002 (1H/1C conventional or up to 2H/1C heat pump with electric aux). Mounted on the UWP push-in wallplate.

Single sourceBrands: Honeywell Home / Resideo2 components

Entry pro-channel programmable stat with a UWP wallplate (push-in terminals, a J-box adapter plate and a small cover plate in the box), battery or C-wire power, and a numbered installer setup (ISU) reached from the advanced menu. Calls: wrong system type or O/B after a swap, heat pump aux not wired on the TH4110U (it has no aux), batteries, and fuses blown during install.

Safety first

Low-voltage (24 V) only; not for 120/240 V line-voltage heaters.
Turn off HVAC power before rewiring to avoid blowing the 3 A fuse.

How it works

UWP wallplate terminals: R, Rc, C, W, O/B, Y and G (the submittal sheet also lists L and K positions on the plate). The heat pump model adds aux/emergency heat outputs.

Power: battery or hardwired (C wire). 'Cool On' and 'Heat On' show when the stat calls.

Installer setup (ISU): press and hold Menu and + for about 5 seconds to open the advanced menu, press Select to enter System Setup, then Select steps through the numbered settings, + / - change them, and Select saves; 'Done' appears at the end.

Programming: 7-day, 5-1-1, 5-2 or non-programmable. Auto or manual changeover.

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Air-source heat pump outdoor unit beside a house in the snow by PeterEastern, CC BY-SA 4.0

Diagnostic guides for this appliance

Guide · Thermostat

Thermostats: alerts and wiring codes vs real equipment faults (Nest, ecobee, Honeywell, communicating systems)

Smart-thermostat alerts are inferred from temperature and runtime trends, not read from the equipment. Google says its System Health Monitor is not a substitute for an HVAC diagnosis. Some thermostat codes are about the thermostat's own power and wiring: Nest E and N codes in one family mean it lost power it was drawing through a call wire, often fixed with a C wire. The equipment fault itself is on the furnace board LED, the outdoor unit or, on communicating systems, in the wall control's service menu.

7 steps ~20 mineasy

Guide · Thermostat

Thermostat cycle rate (CPH) settings: matching the setting to the heating and cooling equipment

Many Honeywell/Resideo and similar digital thermostats use a cycle-rate setting (cycles per hour, CPH) instead of an adjustable heat anticipator. The number tells the thermostat how often it is allowed to cycle the equipment at about a 50% load. A setting meant for an electric furnace on a steam boiler gives short, inefficient firing; a steam setting on a forced-air furnace gives big temperature swings. Check the system type, then set heat, auxiliary/emergency and compressor cycle rates to match the equipment. This is a settings job: no wiring changes and no gas work.

5 steps ~15 mineasy

Guide · Thermostat

R, Rh and Rc: when to keep the jumper and when a system has two transformers

Most forced-air systems have one 24 V transformer at the furnace or air handler, and R and Rc are tied together (a factory jumper or an internal link in the thermostat). Some homes, usually a boiler or older furnace for heat plus a separate air handler or add-on AC, have two transformers: one for heat on Rh/R and one for cooling on Rc. Joining two transformers through the thermostat can blow fuses or burn transformers. Decide which you have before landing wires, and pick a thermostat that supports separate Rh and Rc when there are two.

5 steps ~30 minmoderate

Other thermostats manuals

Manual · Thermostat

Google Nest Thermostat (2020, mirror face, no ring): quick sheet

Google Nest Thermostat launched October 2020 (model G4CVZ, sold as GA01334-US and color variants). Not the Nest Learning Thermostat (3rd/4th gen) or the Nest Thermostat E, which have their own sheets/notes.

9 components5 common failuresGoogle Nest

Manual · Thermostat

ecobee3 lite smart thermostat (EB-STATE3LT-02 and Pro EB-STATE3LTP-02): quick sheet

ecobee3 lite retail (EB-STATE3LT-02) and contractor/Pro version (EB-STATE3LTP-02). Now listed as discontinued by several distributors but very common in the field. ecobee Premium/Enhanced have their own sheet.

9 components5 common failuresecobee

Manual · Thermostat

Honeywell Home T5 / T5+ Smart Thermostat (RCHT8610WF, RCHT8612WF, RTH8800WF): quick sheet

Honeywell Home / Resideo T5 Smart Thermostat RCHT8610WF (no C-wire adapter in the box), T5+ RCHT8612WF (ships with the THP9045A C-wire adapter) and RTH8800WF retail variant. T6 Pro, T9 and T10 have their own sheets.

7 components5 common failuresHoneywell Home, Resideo