What are the electrical specifications for the thermostat terminals?
The thermostat operates at 20-30 Vac (50Hz/60Hz). Running currents vary by terminal: W (heating) and Y (compressor) handle 0.02-1.0A, G (fan) and O/B (changeover) handle 0.02-0.5A, and E (emergency heat, TH3210U only) handles 0.02-0.5A.
From the official Honeywell T3 Pro Programmable Thermostat manual, page 10
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