If you live in San Diego, there are a number of benefits in knowing how to use your heating system’s serial number. First, it tells you in what year the furnace was manufactured, so you can supply that information when you need furnace repair or maintenance. Knowing your system’s age is important because it can tell you a lot about whether you might be able to get by with furnace repairs; or be forced to completely replace the heating system with a new one.

The most popular furnaces that have many years in the field include Carrier, Bryant, Lennox, Rheem and Goodman/Amana. Each of these brands have their own methods of identifying system age from serial numbers.

Most furnaces have a useful and “safe” life between 15 and 20 years. Knowing your furnace system’s age is also important when it comes to the issue of connecting it to an air conditioning system. Most people don’t know that if you want to add air conditioning to your home, your furnace has to be compatible with the new air conditioning system. There are two components to an air conditioning system: the cooling coil or “indoor” component, and the big gray or green outdoor unit, called a condenser.  If you have an older furnace, it most likely won’t be compatible with the newer coil, and subsequently, the newer outdoor air conditioning condenser.  Today’s air conditioning systems provide super high energy efficiency  – but they won’t deliver these kinds of energy savings when paired with furnaces that use older and outdated technologies.

Finding the serial number on your furnace may differ from these general guidelines, but be patient – it might take a little foraging to find it. Try these tips first:

Remove the metal door on the exterior of your furnace.  You’ll usually find this along the bottom part attached to  the front of the unit. Inspect the interior of the metal door – you might see a a label or tag with the furnace’s serial number. If you’re lucky, it could also show the actual date of manufacturer.

If you can’t find the serial number or date of manufacture, switch off the furnace’s power and view the fan and its blades. If you have an older furnace, they sometimes had serial numbers stamped into the metal of the fan itself.

Where to find a Lennox Serial Number on your Furnace in San Diego

The model and serial numbers for Lennox Furnaces can be found by unfastening the top-front service panel.  Look down the left side of the interior furnace housing, or on the top of the blower deck. The efficiency rating – whether your system is an 80% or 90% AFUE, plus whether the furnace is a horizontal or vertical unit, will also determine where you will find the serial number.

Lennox furnace efficiency affects serial number placement







Where to locate a serial number on a Rheem Furnace or Air Conditioner

On Rheem furnace and air conditioning systems, there’s always a letter in the middle of the serial number.  Look at the first two digits after the letter. The first two numbers are the week that it was manufactured. The next two numbers – the  third and fourth numbers after the letter – are the year the system was manufactured. You can also cross check the serial number info with a month and year shown here the upper right part of the data plate. Therefore, “G0994” in the serial number pictured here, means the unit was manufactured during the 9th week of 1994.

How to find a rheem serial number on your furnace or AC





How to Determine System Age on Carrier, Bryant and Goodman/Amana furnaces

Other furnaces made by Carrier, Bryant, Goodman and Amana have their own methods of determining system age. Here are some useful links to their sites where you can find info on system age for many different manufacturing years:

Carrier – http://building-center.org/carrier-hvac-age/

Bryant – http://building-center.org/bryant-hvac-age/

Goodman – http://building-center.org/goodman-hvac-age/