Can't figure this 3 wire system out or find anything in postal about it

Hvac Color Code Wiring

Wiring electrical color code ac wire colour codes cable old plug colours power do chart house british lighting circuit electronic Can't figure this 3 wire system out or find anything in postal about it

Hvac color code Thermostat wiring wire heat color diagram pump air nest guide common goodman colors honeywell code labels heater aruf handler wires Ac plug wiring color code

Hvac Color Code

Hvac wire wiring thermostat color code rh rc ac control terminal do volt 24 common red jumper terminals furnace heat
Can't figure this 3 wire system out or find anything in postal about it
Can't figure this 3 wire system out or find anything in postal about it

Ac Plug Wiring Color Code
Ac Plug Wiring Color Code

Hvac Color Code
Hvac Color Code