How do I identify and label wires in my gang box?

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Danger: The installation of high voltage equipment should be performed by a qualified electrician. Please ensure that you comply with local electrical codes and regulations. Improper installation can lead to device failure and even cause a fire. Damage to thermostat due to improper installation is not covered under warranty.

You can determine which cable is coming from the electrical panel and which cables go to the heater by using a voltmeter. Reference the tables below, to determine the identification voltages. To determine if you have a 240V or 120V installation, read here.

240V Installations

Gang Box Wires Identification Voltages 
Second Phase Leg (L2) (240V)  Ground to L2 (120V)
Supply Wire (L1)  Ground to L1 (120V)
Load Wire  Ground to Load (0V)
Group/Copper  N/A 

 

120V Installations

Gang Box Wires Identification Voltages 
Neutral Wire Ground to N (0V)
Supply Wire (L1) Ground to L1 (120V)
Load Wire  Ground to Load (0V)
Group/Copper  N/A 
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