Hi I purchased a new Honeywell CT87K thermostat to replace my old one. However my old thermostat has numbered terminal codes (4, 5, 6) instead of letters. My old thermostat was connected using 3 wires (red, green, white). Newer thermostat has standard letter terminal codes like R,Y,W... etc. I can't find any correlation info between number terminal codes and letter codes. I am having a lot of trouble installing this thermostat. Please help!