The model/serial are on equipment rating plates, not the thermostat. Indoor and outdoor units have separate identifiers. On a furnace the plate is usually inside the blower compartment door or on the cabinet side, and on an outdoor unit it is on the side panel near the service valves. A heat pump system has one plate indoors and one outdoors.
What this covers
- Residential furnaces, air handlers, heat pumps and central AC
What it does not cover
Try in this order
0 of 7 completedCapture the exact state
ReversiblePhotograph each full rating plate.
Separate the likely fault domains
ReversibleRecord which identifier belongs to furnace/air handler, outdoor unit, coil and thermostat.
Correct only the proven, accessible condition
ReversibleUse exact prefix and serial range with the diagnostic legend.
Find each unit's own rating plate
ReversibleThe furnace or air handler has a plate on the cabinet, often inside the blower door or on the side. The outdoor unit has its own plate on a side panel. The thermostat is not the equipment and does not carry these numbers.
Record which number belongs to which piece of equipment
ReversibleWrite down the furnace or air handler model, the outdoor unit model, the coil model if there is one, and the thermostat model. Label them clearly, because manuals and codes are specific to each piece.
Note the fuel, the voltage and the manufacture date
ReversibleRead the plate for gas, electric or dual fuel, the supply voltage and the date code or serial. Those decide which service literature and code chart apply.
Verify once before going farther
ReversibleConfirm literature matches equipment type, fuel and voltage.
Lennox
Where the identification plate is on a furnace
The plate is inside the cabinet, and where it is depends on the furnace's efficiency class and orientation.
- Lennox furnace
- Remove the top-front service panel and look on the left side of the interior cabinet or on the top of the blower deck, depending on whether it is an 80% or 90% AFUE unit.
- Orientation
- Lennox notes that whether the furnace is horizontal or vertical and whether airflow is downward or upward may change where the plate is.
- Other Lennox products
- On other Lennox products the plate is mounted on the outside of the unit.
Stop boundary
When this stops being a self-service repair
- !Switch off the furnace at its service switch before opening any door, and do not touch wiring or the gas valve; call a technician if you cannot read the plate safely.
Evidence ledger
Sources behind this answer
Exact questions
Common questions about “Where to find a furnace, air-handler or heat-pump model number”
Where is the model number on a furnace?+
On the rating plate inside the front panel or blower door, or on the side of the cabinet. The plate is also where the fuel and the electrical rating are printed.
Why is a separate number needed for the outdoor unit?+
The indoor and outdoor units are made and matched separately, so each has its own model and serial. A code or a part list applies only to the unit it belongs to.
Can I read the plate without opening the furnace?+
Sometimes through the front door's viewing area or a label on the outside. If you have to open a panel, switch power off at the service switch first and stay clear of the burners and the wiring.
Why is the plate in a different place on mine?+
Lennox says the orientation and airflow direction of the furnace can change where the identification plate is positioned.
Which unit holds the label on a furnace and heat-pump system?+
Each piece has its own plate. The furnace or air handler is indoors, the condensing unit or heat pump sits outside, and the coil may carry a third. Record all of them because compatibility depends on the pairing.
Can I read the model from the thermostat?+
Usually not. A thermostat shows its own model, not the equipment's. Some smart thermostats list detected equipment, but the rating plate on the furnace or outdoor unit is the reliable source.
Is it safe to open a panel to reach the label?+
Turn off power at the switch and breaker first, and only remove a door panel the manual describes as customer-removable. If the label is behind fixed panels, use the paperwork from installation or ask the installer.