Installing new thermostat
 

So i bought one of those new wifi thermostats from Costco the other day. Tried to install it today, but when i removed my old thermostat, found only 2 wires where attached. A red and a white wire, connected to the "r" and "w" terminals. 6 wires were cut off and left open/empty behind the thermostat. Yellow, blue, orange, brown, green and black. (black isn't visible in pic, but it is there)
The old thermostat uses 2 AA batteries too. This should be a basic hook up, as i don't have A/C nor a heat pump.

The instrictions say the new wifi thermostat needs a "c" wire 24 VAC common hooked up in order to work. Doesn't look like the old thermo uses a "c" wire. Any idea's which of those cut wires would be a "c" 24 VAC common?

Is this for central heat (furnace) or electric baseboards?

Looks like it should be the former, just want to make sure...

central heating, furnace.
I think i figured it out. I went down to the furnace and found the other end of those six cut wires there. They too were left open and un-attached to anything. I just have to pick a wire and attach it to the "c" terminal on the furnace and the c terminal on the thermostat. But will first have to solder an extension to one of those wires behind the thermostat. They've been cut too short and will not reach the thermo terminals.
Went to the Honeywell wifi thermostat support website and found multiple video's on how to install and what to do if problems arise...such as no c wire's.

The thermostat operation is pretty simple: connecting those two wires together signals the furnace to turn on; separating them tells it to turn off. Likely someone just used some "leftover" eight-conductor bell wire for it.

Not sure why a separate wire would be needed, if the 'stat has its own battery power, as the output should simply close the contacts of a relay to connect those wires.

Before you worry about that "C" connection, try just connecting the two and firing it up. If it does turn out it needs the "C", don't even mess around with soldering; just use whatever short length of wire and twist the ends together. What you're connection is essentially just a ground wire, so you're not going to get zapped off it.

The old stat uses battery power. The new wifi stat doesn't. the C wire will supply the power to the new stat. I haven't tried connecting the 2 wires (red and white) together, but i'm sure it will work. All is working as it should now, with the old stat still in use.

Ahhh okay, now I follow...

if you havnt realized, they are color coded...

O/B - Orange / Black
Y - Yellow
C - Cyan (Blue)
R - Red
G - Green
W - White

Notice it also says, "C is optional with batteries", so if this new stat can be battery-powered, just do that and forget the C wire.

ya it says "c is optional with batteries". But that is the old stat. the new stat doesn't take batteries and says onthe intructions, must have c connection to work

Your furnace probably doesn't have a "c" wire, as it probably doesn't have a 24VAC transformer built in (Typicall of older gas/oil furnaces)

If the new stat won't take batteries (I know Honeywell WiFi stats don't because of power draw), you'll have to install & wire up a 24VAC transformer for power.

If there's a receptacle near your furnace, you can buy a plug-in model,
Otherwise you can install a hard-wired transformer tapping your furnace's power feed (assuming 120V).
Then you just use two spare wires in your t-stat cable.

On your honeywell stat, you'll have to remove the factory jumper between "R" and "Rc"

Your two existing "Heat demand" wires will go to "R" and "W"
Your two new 24VAC wires (24VAC & Common) go to "Rc" and "C"

the furnace does have a c wire, i just found by watching this support video:
explains from 3:10 to about 4:10
the pic below is my furnace with the panel off. Found the other end of those loose wires and will just hook one of them up the c. I think i'll go with the blue wire.
Thanks for everyones input!

Score!

That make it easy.