Where do I connect the W/E wire on the Nest Thermostat?

[qtipper1]

I am attempting to install the Nest Thermostat E (non learning model), and I do not know which terminal to connect the W/E wire to on the Nest Thermostat. I have read that the W is primary heat, while E is for emergency backup. There is only 1 wire going to the W/E terminal on my setup. I am guessing that the wire should be connected to either W1 or W2 on the Nest Thermostat, but I would like correct confirmation. 

Appreciate any additional information.

[Patrick_Caezza]

@qtipper1 

Post a picture of the current thermostat's wiring here.

Where it should go depends on the current thermostat's wiring.