How do I find out what size AC unit I have?
Confusing equipment labels and a lack of documentation make it difficult to know what you are looking at or what size AC unit you actually have. Without clear specifications, people cannot figure out whether a 12k BTU capacity is enough or if an 18k unit is required for hot summer conditions.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Reading the model number or specifications on the outdoor unit labelDid this help you?
- 2Checking the installation booklet left at the indoor air handlerDid this help you?
- 3Posting photos online for professionals to identifyDid this help you?
- 4Estimating based on supply and return air temperaturesDid this help you?
- 5Getting manual J calculations done by different HVAC companiesDid this help you?
- 6Consulting with more experienced installers for their opinionDid this help you?
- 7Relying on historical performance of the existing system on hot daysDid this help you?
- 8Charging by subcooling and superheat rather than a flat numberDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“I’m mainly trying to figure out whether 12k BTU is enough or if 18k would be more appropriate for Arizona summers.”source ↗
“I've got an existing 3.5 Ton single-speed condenser/compressor. I'm looking to replace this with a multi-speed/two-speed Trane, but the options are 3 Ton or 4 Ton, no 3.5 Ton.”source ↗
“Some a/c companies tell me I should go 3 Ton two-speed some tell me I should go 4 Ton and the compressor won't run flat out all the time during the summer.”source ↗
“Let me know if any of you have faced this delimma and which way I should go.”source ↗
“Can anybody clarify for a 3 ton outside unit, why different brands have different refrigerant capacity?”source ↗
“I can’t seem to find out what size unit I have.”source ↗
“I have but I don’t really know what I’m looking for.”source ↗
Where this came up
People with this problem also raised
- 2Can you pair a larger air handler with a smaller condenser?
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- 7How to cool a house without ducts or ugly wall units
- 3How to cool down a house when the AC breaks during a heatwave
- 94Landlord built a fence around the AC and it broke
- 16How to know if my HVAC air filter is the right size?