Honeywell RTH6580WF Wiring: C Wire, Jumper and Heat Pump Setup

1. Check your system first

Honeywell Home’s RTH6500WF configuration article links the RTH6500WF Smart Series User Guide as the guide for the RTH6580WF, and that is the guide this article follows. It says the thermostat works with common 24 volt systems: forced air, hydronic, heat pump, oil, gas and electric. It will not work with millivolt systems such as a gas fireplace, or with 120/240 volt systems such as electric baseboard heat. See our line voltage thermostat guide if you are unsure.

Then, with the power off, look at the old thermostat. If no wire sits on a terminal marked C, or there is no C terminal, read section 5 before going further.

2. Where each wire goes

The wallplate has nine screw terminals. In the guide’s wiring picture, each one carries a conventional label and a heat pump label, read in the same order:

Go by the letter on the old terminal, not the color: the guide says “Do not label by wire color.” Our wire color guide explains why colors are unreliable. B and X mean different things on different equipment, so check our pages on the B wire and X and X2 wires before connecting either one.

3. Wiring it, step by step

These steps follow the user guide and the Quick Start Guide. Our guide to replacing a thermostat safely covers the same ground for any model.

1. Switch off power at the breaker box or the system switch. Confirm it is off by trying to turn the system on at the old thermostat.
2. Remove the old faceplate, leave the wires connected, and photograph the connections.
3. Label each wire with the supplied sticky tags as you disconnect it, using the old terminal letter. Write the letter on a blank tag if no tag matches.
4. Remove the old wallplate, then pull the new thermostat and its wallplate apart using the finger holds.
5. Mount the new wallplate. If you need new holes, drill 3/16 inch for drywall or 7/32 inch for plaster.
6. Connect the wires, starting with C. Loosen the screw, insert the wire on the inside edge of the terminal, and tighten the screw. Tug each wire gently.
7. Deal with the jumper as described in section 4, then push spare wire back into the wall.
8. Fit the quick reference card in the slot on the back of the thermostat and snap the thermostat onto the wallplate.
9. Before power-up, confirm the C wire is connected at the thermostat and at the equipment, and that the furnace door is closed. Then switch the power back on and set the clock.
10. Set function 1 if your system is anything other than a single-stage gas furnace with air conditioning (section 6).

If the screen stays blank, test for 24 V between R and C with our multimeter guide.

4. Heat pumps: O/B, AUX/E and the jumper

The guide has a separate heat pump wiring key. Our heat pump wiring guide explains what each wire does. From the key:

• O wire, no B wire: O goes on O/B.
• Separate O and B wires: B goes on C and O goes on O/B. If another wire is already on C, which is normal because this thermostat needs one, the guide sends you to honeywellhome.com for help. Do not stack wires on C on a guess.
• Separate AUX and E wires: put both wires in the AUX/E terminal. If AUX has a jumper to E on the old thermostat, put the AUX wire on AUX/E; no jumper is needed.
• Separate Y1, W1 and W2 wires, or both V and VR wires: the guide sends you to honeywellhome.com for help.
• R and RC: leave the metal jumper between R and RC in place.

On a conventional system the jumper rule is different. Remove the jumper only if you must connect both R and RC. If the old thermostat had R and RH wires, the guide says to remove the jumper, connect R to RC and RH to R. Our Rh and Rc page explains why two transformers need separate terminals.

The L terminal shares its position with Y2. See our page on L, S and T terminals for what that wire carries.

5. No C wire

The user guide gives one fix: look for an unused wire pushed into the wall, connect it to C, and check that it is connected to the 24 VAC common at the heating or cooling system. Not every system labels the common C, so check the equipment manual. The guide also points to Honeywell’s Alternate Wiring videos at honeywellhome.com/wifi-thermostat.

The guide does not describe a C-wire adapter for this model, and it marks the K terminal “do not use”. That is the main difference from the RTH9585WF, whose adapter moves Y and G to K and C. If there is no spare wire, running new thermostat cable is the option the RTH6580WF guide supports; our guide to running new thermostat wire covers gauge and conductor count, and the no C wire guide compares the other routes.

6. Function 1 and 2 setup, and troubleshooting

The thermostat ships set for a single-stage heating and cooling system. To change it, press Fan and the up arrow together for about 3 seconds. The larger number on the left is the function, the smaller number on the right is the option. Press Next to move between functions and Done to save. The options that depend on your wiring:

• Function 1, System Type: 0 heat/cool (default), 1 heat pump without backup heat, 2 heat only, 3 heat only with fan, 4 cool only, 5 heat pump with backup heat, 6 two heat and two cool stages (W, W2, Y, Y2), 7 two heat and one cool stage, 8 one heat and two cool stages.
• Function 2, Heat Pump Changeover Valve: 0 if you connected a wire labeled O to O/B, 1 if it was labeled B. Honeywell’s support article on heat pump heating says O/B is most commonly energized in cooling, and that Rheem and Ruud heat pumps need it energized in heating. Our O/B page explains the difference.
• Function 3, Heating Fan Control: 0 for gas or oil heat (the system runs the fan), 1 for electric heat (the thermostat runs the fan).

From the guide’s troubleshooting table:

• Blank display: check the breaker and system power switch, close the furnace door, and make sure the C wire is connected.
• Cannot select Cool, or heat runs in Cool mode: check function 1.
• Fan does not run with heat: check function 3.
• “Cool On” or “Heat On” flashing: compressor protection is engaged. Wait 5 minutes.
• Heat pump blows cool air in Heat or warm air in Cool: check function 2.
• Heating and cooling run at the same time: check function 1, then pull the thermostat off and make sure no bare wires touch.

For anything else, work through our thermostat troubleshooting checklist.

7. Frequently asked questions