https://www.heatingair.org/ How to Identify your type of thermostat? The most simple way is to observe your home heating system and then look at the backside of your thermostat. If your home heating/air conditioning system is central (a central furnace or boiler) and you have many ducts or pipes going through all rooms (starting from the furnace/boiler) you should be having low voltage thermostat in your home.Now when you look at the backside of your thermostat, if you see 6 or more wires (thin, multi colored) in its back (going into a board) you can confirm you have a low voltage thermostat. A line voltage thermostat is used only with single stage heating systems (like forced fan heaters or baseboard heaters) and their will be only either 2 wires or 4 wires coming out of its back. These wires will be thick (as they carry higher current & voltage) and often will be in a combination of Black & Red or Black & White color. Well, this is the most important classification when it comes to types of thermostats. In fact, there are only two types of thermostats – either low voltage or line voltage. The other classification (based on features) which brings in Smart Thermostats, Programmable, Non Programmable etc. applies to both line voltage and low voltage thermostats. Smart Thermostats are available for both low voltage & line voltage categories. Similarly, programmable & non programmable thermostats are also available in both categories. So lets see which all are the best models available for both categories and how they differ.

I climb up the attic open the door at furnace and find out there is a transformer that step down 120 v to 24 v . and two terminals at the second end (24v) red terminal is power 24v and the other terminal is use to connect to frame or chassis and serve as common ground so a c wire is any unused wire you can pick any color you want in the same bundle that goes from the furnace to the thermostat in my case those extra wires are trim flush to the bundle jacket on both end so I need to peel that jacket off about 2 inches on both end and connect a single wire about 2 foot long from the frame to the wire you selected (let say black) on the furnace end then the black wire on the thermostat end will be "C" wire and connect it to the "C" terminal on the new wifi fancy Honeywell or Nest. If I say anything wrong please correct me. I will do this at some other time. for now I just thinking. I signed up for smart (something) at gapower.com and they will sent me a nest gen.3 for free. I think this nest also will need "C" wire. I wait till I get the Nest then I will install both the Nest and the Honeywell at same time I will put the Nest down stair and Honeywell up stair.

It appears you have wired the new thermostat correctly. How long does the blower run before the condenser kicks in? How long are you waiting between attempts of lowering the thermostat temperature in order to start the condenser? What might be happening in the new thermostat is the the G terminal is energized immediately which turns on the blower, and the Y terminal has a delay and energizes after a period of time. On most furnace control boards the Y terminal also turns on the blower. So as an experiment try disconnecting the G terminal and then lower the thermostat enough to turn on the AC. The blower and condenser should turn on at the same time. The clunking you hear is probably the condenser contractor closing. I don't see how changing the thermostat would affect the noise level.

Your colors are weird. But lets just list the (non)standard ones: Red = Power Green = G Fan Yellow = Y Compressor (this can be AC or Heat in a heat pump system) White = W Heat Blue = O/B Reversing valve (for a heat pump system). Something Else (Black maybe)= W2 Auxiliary Heat for a heat pump, or 2nd stage heat Something Else (Orange maybe) = Y2 2nd stage cooling Rc is for cooling systems that are separate and distinct from a heating system. Hence two transformers. Normally, R(h) and Rc are shorted together, which is probably what is going on when it says '1 WIRE'. What do you mean by 'aux'?