Jumper wire from C to R?

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Old 03-15-19, 04:40 PM
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Jumper wire from C to R?

Hi, I'm looking to upgrade to a smart thermostat. Looked at my current setup, and I can't seem to figure out the C wire situation. I can identify the following wires coming out from the wall and into the terminals:
Green
White
Yellow
C

Except, in addition to the red colored wire going into C, a jumper cable connects C to R.
what does this mean? It seems like there is a dedicated C wire, but what does it mean that a jumper connects to R? Is this compatible with smart setups that require a C wire?

Attaching a pic that shows current setup.
Thank you for your help!

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Last edited by PJmax; 03-15-19 at 05:32 PM. Reason: reoriented/resized picture
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Old 03-15-19, 05:01 PM
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Hi, R & C should not be jumped in normal operation, what model Tstat do you have ? check at the furnace and see if you can identify where these conductors are connected, also some pics may help, is there AC with this system?
Geo
 
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Old 03-15-19, 05:08 PM
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Thank you, Geo! This is a house I just closed on a few hours ago. The seller replaced an old hvac system, and today was the first opportunity I had of inspecting the wiring. Yes, there is AC with this system. I will be able to post additional pics of the furnace end conductors tomorrow. But are you suggesting that this is a potentially dangerous setup and that I should disconnect it in its current configuration?
 
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Old 03-15-19, 05:11 PM
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The current digital thermostat is an Emerson 1F78-151 Single Stage Programmable Thermostate. I am looking to upgrade to either Sensi Touch or Ecobee 3 lite.
 
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Old 03-15-19, 05:25 PM
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You have four wires to your thermostat.....
White - W
Green - G
Yellow - Y
Red - R and Rc

You will need more wires to get a C connection to your thermostat.
If you use the Ecobee..... it should come with a PEK extender to generate a C connection.
 
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Old 03-15-19, 05:45 PM
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Got it. Thank you!! I was mistaken about the C terminal. Pete, you are correct, it is a jumper between R and Rc. I just found the C cable bundled in the wall, unconnected. Thanks, again!
 
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Old 03-15-19, 06:50 PM
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Wow....an extra wire. You lucked out. If you can't find the C connection at the furnace... post a picture.
 
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Old 03-16-19, 02:16 PM
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Heres a picture of the furnace board. There is a blue wire that is coiled at the base but not connected. At the thermostat end, i see a blue wire coiled around all wires but again unconnected. Im guessing this is an extra wire that I can connected to C terminals at both furnace and thermostat? Thank you for all your help!

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Old 03-16-19, 04:27 PM
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Yes.... the blue thermostat wire goes to C at both ends. There will be two wires on the C terminal at the furnace. I labeled the other two cables as A/C. One goes to the outside condenser and the other goes to a float switch.
 
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Old 03-17-19, 09:15 AM
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Thanks again! So if I am understanding you correctly, the a/c wires are already set up as they should be with the C terminal. All that needs to be done is adding the blue wire to C? I don't need to change anything else in the current setup, do I?
 
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Old 03-17-19, 09:34 AM
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Hi, If everything works correctly now just transfer the conductors from the old Stat to the new one and connect the C to the new the new Stat.
What is the model of your new Stat?
Geo
 
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Old 03-17-19, 09:37 AM
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We've covered the wiring in depth.
Your new thermostat will need to be programmed for your system.
 
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