How to find and read your unit's rating plate
- Takes about 5 minutes
- Beginner-friendly
- 2 tools needed
- Updated
- Reviewed by a licensed tech
Every fitment answer starts with your model number, and it is on a metal or foil plate somewhere on your unit. Here is where each type hides it, and how to tell the model number apart from the four other numbers printed next to it.
What you'll need
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Phone torch and camera
The plate is always in the worst-lit corner of the cabinet. Photograph it — you will want it again.
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Damp cloth
Twenty years of dust turns a foil label into a blank. It usually wipes straight off.
The fix, step by step
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Know which number you are looking for
A rating plate carries four or five numbers and only one of them is the model. Look for the label "M/N", "MODEL" or "MOD". "S/N" is the serial — unique to your box and useless for fitment. There is usually also an AHRI number, a gas input rating and a bar code. Photograph the whole plate: the serial dates the unit, which matters when a model had a running change.
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Gas furnace: inside the burner door, on the divider
Open the lower door. The plate is on the sheet-metal divider inside — often on the left, facing you, or up on the roof of the compartment where you have to look up to see it. Some manufacturers put a duplicate on the outside of the blower door.
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AC or heat pump: on the outdoor cabinet, near the line set
It is a foil sticker on the side of the outdoor unit, usually the face where the refrigerant lines enter, low down. That is the corner that collects grass clippings and weathers hardest, so wipe it before you decide it is unreadable.
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Water heater: the front, under the branding wrap
Usually a paper or foil label on the front of the jacket, above or below the gas valve, frequently under the decorative wrap. Tank heaters print the model, the capacity and the first-hour rating together — the model is the one with letters in it.
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Type the WHOLE number, including the suffix
The trailing characters are not decoration. "GMS80804BN" and "GMS80804CN" are different cabinet revisions with different parts, and the letters at the end are frequently the whole difference. If the plate is genuinely gone, the serial number will usually get us there — send us a photo and we will look it up rather than guess.