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- Read your data plate
How to read the data plate on your equipment.
Every furnace, air conditioner, heat pump and rooftop unit carries one. Seven lines on it answer most of the questions we'd otherwise ask on a first visit.
An outdoor unit's plate, line by line.
Find the plate on the side or back of the outdoor unit. The numbers on the left match the notes on the right.
- Model no.
- XX-048-C2B
- Serial no.
- 2319X04521
- Volts / ph / Hz
- 208/230-1-60
- Min. circuit amps
- 26.0
- Max fuse / breaker
- 40 A
- Compressor RLA / LRA
- 18.6 / 110
- Refrigerant · factory charge
- R-454B · 9 lb 4 oz
Illustrative plate — the values are typical of a 4-ton residential unit, not any particular manufacturer's. Layouts vary by brand.
Model number — usually the size
Many manufacturers build the nominal size into the model number in thousands of BTU per hour: 024 is about 2 tons, 036 about 3, 048 about 4. Not every brand does, so we confirm it.
Serial number — usually the age
Most serial numbers encode when the unit was built, often the year and week. Each manufacturer uses its own code; read it to us and we'll decode it.
Volts, phase, hertz
Houses and small shops are usually single-phase 208/230 volts. Larger commercial units are often three-phase. It matters for replacements and for what's in the electrical panel.
Minimum circuit amps (MCA)
The smallest the circuit's wiring may be, in amps. The electrician sizes the wire from it.
Maximum fuse or breaker
The largest breaker or fuse allowed on the circuit. Anything bigger is a safety problem.
Compressor amps (RLA / LRA)
Rated running amps and locked-rotor amps. We compare the real current draw with these to judge how a compressor is doing.
Refrigerant and factory charge
Which refrigerant, and how much the factory put in. It decides the parts and tools a repair needs. US production of R-22 ended in 2020, so older R-22 systems are costly to recharge; newer units use refrigerants such as R-410A, R-454B or R-32.
The furnace has its own plate.
On a gas furnace it's usually inside the front door. It lists input and output in BTU per hour, the gas it's set up for (natural gas or propane), the allowable temperature rise across the heat exchanger, and the electrical rating.
The temperature rise matters more than most people realise: we measure it on every tune-up, because a furnace running outside its range is working too hard or not moving enough air.
For a building, the plates become a list.
On a commercial roof we read every unit's plate and put them on one page: size, age, voltage, refrigerant. That list tells you which units are oldest, which share parts, and which are still on a refrigerant that's getting expensive to service.
It's the first thing we do for a new commercial customer, and it costs nothing to keep up once it exists.
Before you call about your house.
Two lines are enough: the model number and the serial number from the outdoor unit or the furnace. If you can't get to them, don't worry — we'll read them when we arrive.
Safety first
Don't remove panels to find a plate. The one on the outside of the unit or behind the furnace's front door is all we need.
Call and read us two lines.
We'll tell you what you've got before we even arrive.