Whether you need a physical jumper wire between the R and RC terminals depends on your specific thermostat and HVAC setup.
Since R and Rc both often go to the same place on a combined heating/cooling system, it's common to jumper them together at the thermostat and only run one wire. Like other Honeywell thermostats, the Lyric T5 actually has a switch to join the two together instead of a jumper wire.
RH delivers heating power. Each wire comes from a separate transformer when the system has two transformers. Homes with one transformer use a jumper that connects RC and RH, which makes both terminals behave the same. Homes with two transformers keep RC and RH separate to prevent blown fuses and control board damage.
If you have a standard single-system HVAC (furnace and AC), connect the red wire to Rc. If you have a two-transformer system (e.g., a boiler for heat and a separate air handler for AC), connect the heating power wire to Rh and the cooling power wire to Rc.
A jumper between the R and Rc (or Rh) terminals bridges the 24-volt power supply so that a single "hot" wire can operate both your heating and cooling systems.
By serving as a bridge between two locations, the jumper wire enables coordination and communication between the internal parts of the thermostat. The thermostat couldn't precisely regulate the temperature or interact with other appliances in your house without this connection.
In HVAC wiring, R and RC are power terminals, but they are slightly different. R is the general power wire for your heating and cooling systems, while RC specifically stands for "Red Cooling" and supplies power to your air conditioning.
Some units don't have an RH wire, but instead, they have an R wire. An R wire is similar to either the RC or the RH, so if you don't have an RH wire, the R wire will be in place to control the heating system.
The R wire is the primary power supply for your thermostat. It carries low-voltage (usually 24V) power from your furnace or air handler transformer. The thermostat uses this electricity and sends it to other wires (like Y for cooling or W for heating) to activate your HVAC system.
If the black wire on the R terminal goes to the thermostat and only the thermostat, you can safely move it over to the C terminal. The AC and humidistat being hooked up to C is correct. R and C together carry the 24v power that a smart thermostat (and some programmable models) use for power.
it goes into the R terminal, setting the jumper connecting terminals R and RC in place. Thermostats may have a jumper switch, metal staple, or plug. The jumper may also be a wire connecting the two terminals. If you have two wires, R or RH go into the R terminal and RC into the RC terminal.
Yes, a Nest thermostat can work without a C wire in many homes. It powers itself using a technique called "power stealing" by trickling charge from your existing heating/cooling wires.
Whether you need a physical jumper wire between the R and RC terminals depends on your specific thermostat and HVAC setup.
If it's just a 2 wire, connect the wires to R & W. Simple as that. Polarity doesn't matter. Generally they are set up as R for red, W-white, etc.
Nest thermostats don't use jumper wires
Instead of using jumper wires, Nest Learning Thermostats use an internal jumper between the Rh and Rc connectors. A Nest Learning Thermostat will automatically use this internal jumper if your system needs it.
If you have only one red wire, it can generally go to either Rc or Rh. Most modern thermostats (like Nest or Ecobee) have internal jumpers that bridge the power for both heating and cooling.
No, Rccap R c𝑅𝑐 and Ccap C𝐶 are entirely different wires with distinct purposes.
To make a jumper wire for a thermostat, cut a 2- to 3-inch piece of standard 18-gauge to 24-gauge thermostat wire and strip about 12one-half12 inch of insulation from both ends. You can also use a small copper wire or bend a standard metal paper clip into a U-shape.
C-Wire Conundrum: Installing Thermostats Without It
On a thermostat, R and Rh are practically the same for most standard HVAC setups. Both represent the 24V power wire (usually red) that supplies power to the system.
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