Honeywell Lyric T5 Wifi Thermostat Wiring Diagram

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About This Diagram

These diagrams are redrawn from the Honeywell Lyric T5 Wifi Thermostat manual, and we offer them completely free and in English. We have also categorized it in the Thermostats (HVAC & Water Heating) section on Diagramverse, and it has been rated by 1 user with an average rating of 5.0. If you have any specific questions about the Honeywell Lyric T5 Wifi Thermostat Wiring Diagram, we suggest checking the Frequently Asked Questions (FAQs) section.

Printable Honeywell Lyric T5 Wifi Thermostat Wiring Diagrams

Heat only · 1 stage

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Wiring Instructions

Before you start

First, make sure your system is compatible. The Honeywell Lyric T5 Wifi is a 24 V AC thermostat. It works with most single-stage and multi-stage conventional and heat pump systems, and it needs a C wire to run. It does not work with electric baseboard heat (120–240 V) or with millivolt systems. Look at the old thermostat: if it has thick black wires joined with wire nuts, or it is marked 120 V or higher, you have a line voltage system and the T5 cannot be used.

Tools: small flat-head and Phillips screwdrivers, wire stripper, needle-nose pliers, pencil, level, a drill with a 7/32 in bit, and a smartphone with the Honeywell Lyric app. You also need your home Wi-Fi password. The thermostat connects only to a 2.4 GHz network.

Wire: you can reuse the existing thermostat cable. Honeywell does not give a wire gauge. As general practice, use solid copper thermostat cable, commonly 18 AWG. If you have to run a new cable to add a C wire, choose one with a conductor for every terminal you need plus a spare.

Choose the right tab:

• Heat only: a furnace with no air conditioning.
• Cool only: air conditioning with no heat on the thermostat.
• Heating and cooling: a furnace plus an air conditioner. Use 1H/1C · 2 transf. if your old thermostat had separate R (or Rh) and Rc wires.
• Boiler: a hot water or steam boiler, or a zone valve.
• Heat pump: your old thermostat had an O/B wire.

To pick the variant, count your W and Y wires; that count is your number of stages. Replacing a low-voltage thermostat is usually a homeowner job. Call an HVAC professional if you need a new C wire landed at the equipment control board, or if the wiring at the equipment doesn't match what you find at the wall. Permit rules vary, so check locally.

Step-by-step wiring

1. Turn off power at the breaker or switch that controls your heating and cooling. To confirm it is off, change the setpoint on the old thermostat: if nothing starts within 5 minutes, the power is off.
2. Take the old thermostat off its wall plate. Photograph the wiring so the terminal letters are readable. If wire colors are faded or two wires are the same color, label each one.
3. Write down which terminals have wires: first R, Rh and Rc, then Y, Y2, G, C, O/B, W, W2 or AUX, and E. Remove any jumpers and leave them out of your count, because the T5 does not need them. S and U terminals are not supported. If you find wires on other terminals, get further support before you continue.
4. Disconnect the wires and remove the old wall plate. Wrap the wires around a pencil so they can't fall back into the wall.
5. Feed the bundle through the back of the UWP. Strip or trim each wire so about 1/4 in of straight, clean copper is exposed.
6. Set the R switch. With one R wire (R, Rh or Rc), set the switch up and insert the wire into R. With two wires, set the switch down, put the Rc wire in Rc, and put the R or Rh wire in R.
7. Connect the remaining wires one per terminal. Press each tab and push the wire into the inner hole until it seats. On a heat pump, the old W2 or AUX wire goes to AUX and the old E wire goes to E. On a zone valve, the valve motor connects between W and C. Tug each wire gently to check that it holds.
8. Only after the wiring is done, level the UWP and fix it to the wall. Use the supplied anchors and all three #8 1-1/2 in screws, then close the door.
9. Line the thermostat up with the UWP and snap it firmly into place.
10. Turn the power back on at the breaker or switch.

Testing and start-up

Within moments, the screen should show START SETUP. If it stays blank, turn the power off again and check your C and R connections. You can also measure R to C with a meter set to AC volts: expect roughly 24 V AC, and the T5 is rated for 20–30 V AC.

Configure the thermostat with the Lyric app or with manual setup. The settings must match your wiring:

• System Type: Conventional Forced Air, Heat Pump, Boiler or Cool Only.
• Equipment Type for your system.
• Reversing Valve (heat pumps only): O/B on Cool or O/B on Heat.
• Cool/Compressor Stages: 0, 1 or 2.
• Heat Stages: 0, 1 or 2. On heat pumps, Aux/E stages: 0 or 1.

Then test each function. In Heat, set the setpoint above room temperature. In Cool, set it below. Set the fan to On and check that the blower runs. Allow up to 5 minutes for the equipment to respond. On a heat pump, also confirm that Em Heat appears in the mode list.

Safety notes

• Always disconnect power before wiring. Live work can cause electric shock or damage the equipment.
• Compressor protection is bypassed during testing. Don't switch cooling or heat pump modes on and off rapidly, or you can damage the compressor.
• Keep bare ends short so neighboring wires never touch. As general practice, a short between R and C can blow the low-voltage fuse on the control board or damage the transformer.
• The thermostat outputs have current limits. W, W2, Y and Y2 handle 0.02–1.0 A. G, O/B and E handle 0.02–0.5 A. A load above these limits needs a relay.
• In a two-transformer system, never jumper R to Rc. The R switch in the down position keeps the transformers apart.
• If your old thermostat contains mercury, don't throw it in the trash. Ask your local waste authority how to recycle it.

Troubleshooting

Frequently Asked Questions (FAQs)