### Serial Number Sourcing

The model number CRJ3-0300-PVF for the Heil central air conditioner refers to the compressor, produced by Copeland Compressors, a division of Emerson Electric. Copeland manufactures compressors used in almost all major brands of central heating and cooling systems, including Heil. The model number helps to identify the size of the compressor. The size of the compressor is important, as it determines the capacity if the air conditioner.

### Capacity Size Units

The British Thermal Unit -- BTU -- is a measure commonly used today in the cooling and heating industry. One BTU is the amount of heat required to raise the temperature of a pound of water one degree. One air-conditioning ton is equal to 12,000 BTUs. For example, an air conditioner that's rated at 18,000 BTUs is a 1.5-ton system.

### Heil Compressor Ratings

The CRJ3-0300-PVF compressor in a Heil air conditioner is rated at 37,900 BTUs. Converting the BTU rating to tons, you find that this unit has a cooling capacity of nearly 3.2 tons.

### Alternative Models

A similar compressor is model number CRG3-0250-PFV. This model has a cooling capacity of 32,700 BTUs, or about 2.7 tons. An air conditioner with this compressor is considered a 2.5-ton unit. The three-digit number inside the model number specifies the ton rating that the manufacturer has given it. So even though the CRJ3-0300-PVF compressor has a cooling capacity of nearly 3.2 tons, it's rated at 3 tons. You can decode the capacity of your air conditioner from the model number.