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Wiring diagrams and terminal labels
Terminal labels, transformer requirements and wiring notes for thermostats, video doorbells and EV chargers.
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Wiring is the one area where a wrong guess can damage equipment or create a safety hazard. We explain what terminal labels mean and what the manual requires, but we always send you to the installer section of the official document for the diagram that matches your system.
Rh / R24V powerRc / CCommonW / W1HeatY / Y1CoolingGFanO/BHeat pump valve
Wiring by product
Google Nest Thermostat
Nest Thermostat (2020)Before you install: check your wires. This thermostat works with most 24V heating and cooling systems but not with line voltage (120V or 240V) systems like many electric baseboard heaters. 5 steps
Ring Video Doorbell (2nd Gen)
Video Doorbell (2nd Gen)Wiring to an existing doorbell. This doorbell can run on its battery or trickle charge from existing doorbell wires. Ring lists a transformer range of 8 to 24 VAC for this model.
Background reading
- 01
Thermostat wire labels decoded: Rh, Rc, W, Y, G, O/B
What each thermostat terminal letter means, why the C wire matters for smart thermostats, and the safety checks to do before replacing one.
- 02
DANGER, WARNING, CAUTION: what manual safety labels mean
The difference between DANGER, WARNING, CAUTION and NOTICE in owner's manuals, and the common symbols you'll see on products.