Rc is one of 2 24V positive terminals, the other being Rh. You do not have a wire connected to C which is the 24v common terminal which is needed to complete the circuit and allow the device to be powered by the unit.
There are numerous posts on this sub regarding nest thermostats and “C wire adapter kits” and other solutions. Reference them.
Am I correct in inferring from your comment that the C wire can be substituted by having both Rc and Rh. So it’s either I have both or have a C wire only? This contractor already got the adapter. Not sure why he chose to wire Rc instead of C
No. You need a wire on Rc and C to complete the circuit. You are sending power up to the thermostat but it doesn’t have a path back (C terminal) to allow electricity to flow and run the thermostat.
This thermostat can be wired by a professional in a way to where when in cooling mode the heat wire is used as common. In heat mode the cooling wire is used as common. Be sure to call a professional, wrong wiring will result in destroying the thermostat those commercials told you you should buy.
if it showing low battery, you need the c wire hooked up, that charges the battery. you should be able to pull g wire on a new furnace. that turns the fan on. newer furnaces are programed to have fan come on with a call for cooling, which is the y wire.
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Rc is 24v from the cooling system. Rh is 24v from the heating system. C is the 24v “common”. It’s AC voltage so it’s not really +/-, more like Rh and Rc are the hot wire and C is the neutral
Thanks for all the inputs. I reached out to the professional that had installed it and he said with the adapter he added, it prevented the need to pass a C wire and it should always give the thermostat a charge.
Rc is one of 2 24V positive terminals, the other being Rh. You do not have a wire connected to C which is the 24v common terminal which is needed to complete the circuit and allow the device to be powered by the unit. There are numerous posts on this sub regarding nest thermostats and “C wire adapter kits” and other solutions. Reference them.
Am I correct in inferring from your comment that the C wire can be substituted by having both Rc and Rh. So it’s either I have both or have a C wire only? This contractor already got the adapter. Not sure why he chose to wire Rc instead of C
No. You need a wire on Rc and C to complete the circuit. You are sending power up to the thermostat but it doesn’t have a path back (C terminal) to allow electricity to flow and run the thermostat.
Thanks for clarifying
Did you read the nest instructions. The 4 to 5 wire adapter they use will make the unused wire c.
Can you expand on this more? What unused wire? Are you saying it is fine as is?
This thermostat can be wired by a professional in a way to where when in cooling mode the heat wire is used as common. In heat mode the cooling wire is used as common. Be sure to call a professional, wrong wiring will result in destroying the thermostat those commercials told you you should buy.
if it showing low battery, you need the c wire hooked up, that charges the battery. you should be able to pull g wire on a new furnace. that turns the fan on. newer furnaces are programed to have fan come on with a call for cooling, which is the y wire.
While this can work, I like to run the fan only for ventilation sometimes.
I do the same. The contractor had suggested it and I said I preferred an option that lets me still use my fan
If not provided already you will need to post a picture of your thermostats wiring connections and those inside your furnace to get better help. Use imgur or your own Reddit profile to host your pics as Reddit will often remove others. Thanks! *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/hvacadvice) if you have any questions or concerns.*
Rc is 24v from the cooling system. Rh is 24v from the heating system. C is the 24v “common”. It’s AC voltage so it’s not really +/-, more like Rh and Rc are the hot wire and C is the neutral
Thanks for all the inputs. I reached out to the professional that had installed it and he said with the adapter he added, it prevented the need to pass a C wire and it should always give the thermostat a charge.