Nomenclature and How to Use It

Nomenclature on HVAC/R equipment is a sequence of numbers and letters a manufacturer uses to speak directly to the technician. Lots of initial upfront information is handed to the technician by the manufacturer the moment the technician reads the nomenclature in the model and serial numbers.

So how do we make sense of these seemingly random sequences of alphabetical/numerical characters? Every manufacturer has developed its own “language” of sorts when it comes to their equipment. Let’s take a look at several different examples.





Now let’s take a look at all the different information these model numbers can give us. Across the manufacturers listed as examples, we can find information about Product Series, Type of Equipment, SEER, Cooling/Heating Capacity, Grille Variations, Voltage, Configuration, Cabinet Dimensions, Type of Motor, Airflow Capacity, Refrigerant Type, Efficiency, etc.

Understanding the importance of the information in model numbers is essential, and can save a lot of time in diagnosis and installation. Serial numbers, too contain valuable information. Most manufacturers don’t publish the nomenclature for serial numbers, because it’s mostly used for warehouse and warranty tracking, but a few helpful tips per manufacturer are:


Carrier: The first 2 numbers in the serial number indicate the week of the year the equipment was manufactured. The 3rd and 4th numbers indicate the year of manufacturing. 

Goodman: The first 2 numbers in the serial number indicate the year of manufacturing. The 3rd and 4th numbers indicate the week of the year it was manufactured.

Trane: Typically has the year of manufacturing printed elsewhere on the data tag

Mitsubishi: The first number in the serial number indicates the year of manufacturing. The decade must be assumed. (an “8” could mean the equipment was manufactured in 2008, or 2018)


Bottom Line 


Always take a moment to familiarize yourself with the manufacturer model/serial number nomenclature. The information you find will help you understand the system more fully and can help speed up the diagnosis/installation process.



Wide, Narrow, Wide Diagnosis

When you walk up to a piece of equipment you want to follow a process to ensure that you accomplish five things.

#1 – You diagnose the fault correctly

#2 – If possible you find the “why” of the failure

#3 – Find any other problems or potential problems with the system that can cause inefficiency, low capacity, failure, safety or indoor air quality issues

#4 – Communicate clearly with the customer and and office about these issues via paperwork and / or verbal communication

#5 – Execute and repair the issues in an efficient and workmanlike manner

In order to accomplish this I recommend looking at the equipment with a wide, narrow, wide mindset

First, speak with the customer, read the call history, understand any concerns the customer may have and any past failures. Look at the equipment, look for any obvious signs of issues like oil stains, corrosion, rubbing wires, bloated capacitors etc…

Then go narrow and FIND THE CURRENT PROBLEM. The difference between a “Sales Tech” and a real service tech is the ability to quickly and accurately diagnose the problem at hand as well as find the likely causes of the failure.

Finally, once you find THE problem, go wide again and look for any other problems BEFORE communicating with the customer. Look at coils, contactors, capacitors, filters, belts, wire connections and potential rub outs, check coils and accumulator for oil stains etc…

When looking wide take the mindest that..

– The system was likely installed poorly / incorrectly to begin with

– Every other repair made to the unit was done improperly

This will put you in the mindset to double-check everything.

Now you are ready to talk to the customer and make repairs with confidence.

— Bryan


To continue you need to agree to our terms.

en English