Google Nest Thermostat E (2017-2020, frosted display): quick sheet

Covers: Nest Thermostat E, the white, frosted-display Nest sold from 2017 until the 2020 Nest Thermostat replaced it. Six press connectors on the base. Not the Nest Learning Thermostat (3rd/4th gen) and not the 2020 Nest Thermostat; those have their own sheets.

Cross-checkedBrands: Google Nest2 components

A cut-down Nest for simple 24 V systems: one heat and one cool stage plus one extra stage through the multifunction */OB connector, single-speed fan, no humidifier or dehumidifier control, and no support for two-transformer systems. It powers itself through a built-in rechargeable battery and power stealing when there is no C wire. Most calls are wiring choices on the */OB connector, low battery on systems without C, and Wi-Fi.

Safety first

Line-voltage (120/240 V) heaters are not compatible; if the old stat has heavy wires and wire nuts, stop.
Turn off power at the HVAC equipment before moving wires.

How it works

Connectors: Y1, G, R, W1, C and a multifunction */OB. Google's specification page lists support for W1, Y1, W2 or Y2, O/B, AUX, G, C and Rh or Rc; the */OB connector is what supplies the second stage or the heat pump changeover.

When a wire goes into */OB, the thermostat asks what it is during setup (stage 2 heat, stage 2 cool, or the heat pump changeover valve). On a heat pump, W1 is used for the aux/emergency heat.

No jumpers are used. The thermostat joins Rh and Rc internally, which is why the Nest Thermostat E does not work with dual-transformer systems.

Power: 20-30 VAC with a built-in lithium-ion battery. Without a C wire it charges by stealing small amounts of current through the heating or cooling wire; on some equipment that causes clicking, short cycling or a low-battery shutdown, which is when a C wire or the Nest Power Connector is needed.

Google lists compatibility with about 85% of 24 V systems (the Learning Thermostat claims about 95%). It is not compatible with 120/240 V line-voltage heat or millivolt-only systems.

Components & tests

Unlock all 2 components, specs, service mode and teardown

Full library + AI assistant + the OnCall Tech app for iPhone & Android. $34.90, one time.

Get lifetime access

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): Digital thermostat mounted on a concrete wall by Alexander Mass, Pexels License

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