This is the first in a series of posts that I am going to make on how to read the serial numbers for the more popular units in my area. I am going to start with Goodman heating and cooling products out of Houston, TX. These are very common to see throughout the south and here in the Middle Tennessee area. One of the questions that I get asked quite frequently by real estate agents and home owners alike is what the age of the unit and will it adequately cool my house? As inadequate tonnage and older units can lead to considerable expense for the potential home owner, I tell them the approximate tonnage and the approximate age.

Different manufactures have their own system for identifying the age, tonnage, and where the unit was manufactured. But I will start with Goodman since their identification system is fairly standard.

Let’s start with the model number for the compressor units. Package units will differ slightly. The model number usually contains the tonnage of the unit for most manufacturers. Disregard the first three letters as they are not used. The next number 36 is significant as this tells the tonnage. To determine tonnage, take this number (36) and divide by 12. The result is 3. This is the tonnage of the unit. If the number was 30 or 42, the tonnage would be 2.5 or 3.5 respectively. To determine adequacy, the rule-of-thumb is to take the square footage of the property and divide by 650. EX: a 2000 sq. ft property divided by 650 BTU/H = approximately 3 tons of cooling. There are other determining factors such as age of the property, amount of windows, insulation etc. which factor in, but I will not get into this.

The age of the unit is found in the serial number. In this example, the first two digits 02 indicate that this unit was built in 2002. The 09 indicates that it was built in September. Hence September 2002.

As I mentioned earlier, package units, which house both the heating and cooling sections for the property, will differ from compressor units. In this example, the model number contains both the tonnage and the approximate BTU/H for the compressor and the furnace sections. The 024/12 = 2 tons of cooling capacity while the 075 = the approximate heating capacity in BTU per hour. In this case, it would be 75,000 BTU/Hour. Once again, the serial number indicates the age of the unit where the first two digits 01 give the year, and the next two digits 12 give the month of manufacture.

Most other manufactures follow this numbering convention, but there are a few that do their own thing. York is one of the exceptions to this rule. I will post other serial numbers and Manufactures in later posts.

I hope that you have found this information to be helpful. If you have, let me know.

This posting and the contents written here are the intellectual property of Michael Thornton of Complete Home Inspections, Inc. providing home inspections for Brentwood, Nashville, Davidson and Williamson Counties of Middle Tennessee. The views and opinions expressed are just that - views and opinions of Michael Thornton and those who comment. This post is a contribution to the ActiveRain Real Estate Network.