Upgrading to Smart/Wifi Thermostat - No C Wire

[Furby076]

Hello,

I have a Honeywell RTH11B1016 (see pics), that I'd like to replace. It has 4 wires connected G, Y, W and RC. Looking behind, I see another white and red wire connected together. Can someone let me know what this white/red wire are and is it possible to connect these to a smart thermostat that requires a C wire? Or am i stuck using a non-smart thermostat? Really I want a wifi one, but if it's battery operated then it's a pain.

 

[waybomb]

What's connected at the other end of the w/r that are connected together? If not connected, take one of this and make it your c. Get a permanent market and color it black on both ends for the next guy.
C is the common.

 

[Melensdad]

Many of the new "smart" thermostats have a "C wire" conversion kit that is an option. I saw one or two that actually had different model for non-C wire and for C wire units.

Honestly I did a lot of research on these a couple years ago, so my info is from memory from 2-3 years ago. Ecobee (sp?) looks to be the favored brand.

 

[Furby076]

What's connected at the other end of the w/r that are connected together? If not connected, take one of this and make it your c. Get a permanent market and color it black on both ends for the next guy.
C is the common.

I don't know where it connects to as it's in the wall. I know the AC unit is on the opposite side of the wall. Do you think there is harm in plugging it into the C and see if it works? Or is there a way to test (electric tester)?

 

[waybomb]

Of you don't know where those wires go or come from, leave them alone

 

[Melensdad]

Of you don't know where those wires go or come from, leave them alone

Honestly it is a pretty easy job to use a c wire jumper. Everything is color coded. It is low voltage. The manufacturers have great video instructions and there are plenty of YouTube videos. It looks like I could do it, so that makes it idiot proof. Just have to have the right non-c-wire to c-wire adapter kit for the chosen thermostat.

 

[Melensdad]

I don't know where it connects to as it's in the wall. I know the AC unit is on the opposite side of the wall. Do you think there is harm in plugging it into the C and see if it works? Or is there a way to test (electric tester)?

As stated before, you need the correct kit. What you end up with is an expensive thermostat that will not operate as desired/advertised if you don't connect it property.

The non-c-wire kit will typically install at the HVAC unit. If I recall correctly, again I looked at these pretty in depth a couple years ago, the c-wire is typically the 5th wire. The thermostat will be connected by (typically 4 color coded wires). It might be that the C wire is the 4th wire and there are only 3 others? In any case, simple and universally color coded.

The only reason that I did not upgrade was simply because I already had a properly working programmable unit installed and while the HVAC guy suggested he could upgrade me, it was a very expensive proposition for him to do it. So I looked into it and realized it is literally a 30 minute job, with a simple screwdriver, and far far less expensive as a DIY job. But the benefit over a properly working programmable unit is marginal. So I'll wait for my programmable unit to fail and then upgrade.