I just moved into a new home and was trying to connect my Ecobee thermostat. I know it requires a C-wire. I found the wire wrapped around the others in the previous thermostat, which didn't require one. When I connected it to the Ecobee, however, it did not show the display. Assuming then that it was an issue of the C-wire not being connected, I went into the attic and looked at the wiring. Sure enough, the blue wire is there, bit wrapped around the others, not connected. I looked where it should be connected and found that there is a second red wire connected there. My question is, can I connect the blue wire (C-wire) to the same terminal that the red is connected to? It seems like I should be able to.

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    Hello, and welcome to Home Improvement. If the answer is helpful, please click the big checkmark to accept it. And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Nov 14 '19 at 14:21
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    The red wire currently under the C terminal is probably running to your outside unit along with the Y wire. If you were curious... – JPhi1618 Nov 14 '19 at 19:14
  • I connected the C-wire to the same terminal and it worked like a charm – Brad Drake Nov 15 '19 at 3:07

Yeah, go ahead

If you look at the Y terminal on your control module, you will notice that the pressure plate under that terminal screw is already clamping two wires, one to each side. So, this means that you are safe to slide the stripped end of your blue wire under the free side of the C terminal screw's pressure plate and call it good!

  • Just the nudge I needed lol. If the house blows up, I have insurance, but fingers crossed! Thanks, man! – Brad Drake Nov 14 '19 at 5:46

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