How Can I Tell If My Mobile Home Air Conditioner Is The Right Size?


So the old saying “bigger is better” can be true for lots of things, but for the size of your central HVAC unit, not so much. In this case, “size does matter”!

The Short Answer

The data plate in your manufactured home will hold the key as to whether or not your HVAC system is the proper size for the home.

The “Data Plate” is a paper label affixed inside the home and is the size of a standard sheet of paper (8 1/2” x 11”). The Data Plate can be found:

  • In a kitchen cabinet, 
  • An electrical panel, 
  • A bedroom closet,
  • Inside the water heater closet,
  • Or the inside of a bathroom cabinet door. 

On the right side of the data plate, you will find a section called “Comfort Cooling”. In this section, there will be the factory recommended amount of BTU (British Thermal Unit) required to adequately cool the home. This BTU rating can be converted to tonnage by dividing by 12,000. The answer can then be checked against the tonnage of the actual HVAC system on the home.

Mobile Home Data Plate

The label on the HVAC system itself can give you the information needed to figure out the size of the unit.

Typical Manufactured Home HVAC System

Most mobile homes package the central air conditioning systems into one unit. This unit comprises the condenser, air handler, evaporator coils, and compressor all into one unit. This unit generally sits on the ground just outside the skirting to the home.

The HVAC unit is then connected to the ductwork system which runs below the flooring in the home. There will be HVAC registers, generally on the floor, coming up from the ductwork into each room in the home.

For further information on ductwork in a manufactured home, please see our post “How Much Does It Cost To Replace Ductwork In A Mobile Home?”

Why Is Size So Important?

Central HVAC systems to two things to the air in your mobile home. First, they dehumidify the air, (take out the moisture) and secondly they cool the air. If too large of a unit is installed on the home, then the HVAC system will cycle on and off frequently. 

Because a too-large unit will cool the air very quickly, it may not be operating a sufficient amount of time each cycle to adequately remove the humidity to an acceptable level.

If the humidity levels in the home are too high, the coldness of the freshly cooled air and cause moisture condensation to form even inside the walls of the home. This can lead to the formation of hazardous mold. Not a good thing!

The properly sized HVAC unit on the home will run a sufficient amount of time to bring the humidity down to acceptable levels.

Also, HVAC units draw the largest amount of electricity upon the first minute or so after start-up. In addition, the wear on the unit itself is higher the more frequent the start-up and shut down of each cycle. If the unit is constantly turning on and off, it is using more electricity than it might if it were running longer cycles.

Determine If Your HVAC System Is The Right Size For The Home

The data plate for the mobile home, referenced above in “The Short Answer” section is the key to properly sizing the HVAC system to the home.

Step One

On the right side of the data plate, you’ll see a section called “Comfort Cooling”. In this section, you will see the recommended BTU (British Thermal Units) needed for efficient and effective cooling and dehumidifying of the house. For giggles, let’s just assume that it says 21,000 BTUs are needed.

Step Two

Now to figure out the optimum sized unit for the home. HVAC systems are measured in tonnage, so we need to convert the BTUs into tonnage. One ton is equal to 12,000 BTU. So, if the recommended BTU is 37,500 we do the following:

BTU Needed 37,500

Conversion Factor 12,000

Optimum tonnage Size 3.00 tons

Step Three

Go outside to the unit on the home and check the label. Unfortunately, the labels can be tricky to understand and they are no all the same. Some labels will list the BTUs, maybe 60,000. If your unit lists the BTU size, then do the same as above and divide by 12,000 for the tonnage size.

In our experience, it seems more often than not, neither the BTUs or the tonnage is listed on the unit’s label. If not you have to go to step four.

HVAC Unit Label

Step Four

Take the make and serial number, call a local HVAC company and they should be able to look up your unit and tell you the size. If you are replacing your unit, it is wise to go with the properly sized unit for maximum efficiency.

But My Data Plate Is Missing

Not to worry. This happens quite often with older mobile homes. The U.S. Department of Energy has a program called “Energy Star”. This has been around for years and you may have heard of it. They have an excellent PDF file that is downloadable

Just follow this link to download your copy – “Manufactured Home Cooling Equipment Sizing Guidelines”.

Beyond Sizing What Else Do I Need To Be Concerned About?

Inadequate Charging

Studies indicate that more than 60 percent of existing HVAC units to not have adequate coolant charging upon installation. During installation, the contractor will need to adjust for the length of piping between the indoor and outdoor parts of the unit if it is a split system.

Air Leaks

It is also estimated that the average residential ductwork system will lose about 30% of the conditioned air to leaks in the ductwork, usually into attic space above or the crawl space underneath the home. It is a wise idea to check the ductwork system at least annually to look for potential leaks.

Related Questions

“What Is The HUD Tag And Where Do I Find It On A Mobile Home?”

The HUD tag, required to be attached to a manufactured home, is important for may reasons. We have purchased, been given, or acquired “somehow” many older mobile homes that we have renovated and flipped. In order to sell these homes, we have to have a title, a VIN number and often are required to reference the HUD tag as well as the home’s data plate. So where can all this be found? And … what does any of it mean?

The tag, issued by HUD (Department of Housing and Urban Development) is a 2” by 4” plate made of metal that is attached to an exterior wall of each section of a mobile home. A single wide has one tag, and a double-wide will have two tags. In general, people will refer to this as the HUD label.

This metal tag generally should be attached to the rear of the home, usually about a foot from the side and a foot up from the bottom. This has been required by HUD on every manufactured home built since June of 1976.

How Can I Get Rid Of Dampness And Mold In My Mobile Home?

Water and humidity in any home, site-built, modular, or manufactured can cause problems for any homeowner. In fact, water remediation (restoration) is a $210 BILLION dollar business in the United States. In case you’re wondering, that is A LOT!

When water gets trapped in spaces such as attics, walls, crawl spaces, carpets, wood subfloors, etc. mold can develop. Mold is a common health hazard and causes all types of respiratory issues.

Remember the old saying “an ounce of prevention is worth a pound of cure”? That is absolutely the case when it comes to getting rid of dampness and mold inside of a mobile home.

Most folks think that water damage inside of a home comes either from leaking plumbing or a leaky roof. While those are both true, that is only the beginning. Sealing out moisture, whether from the roof, windows, doors, floor, skirting or ground is necessary to prevent the buildup of dampness and mold. Keeping the moisture away to begin with is the ultimate weapon against buildup of dampness and mold.

Chuck O'Dell

Chuck has been renovating and flipping properties since 2003. At this point he has over 100 properties under his belt. Chuck says that rehabbing homes is the most fun part of his real estate career. He helps clients get their homes ready to sale, helps his buyers with after-purchase remodeling; often very substantial renovations including full kitchens and bathrooms. Chuck started investing in, buying, renovating, selling, and flipping manufactured homes both in parks and on their own fee-simple lots. He says that one of the most satisfying part of renovating the mobile homes is creating beautiful, affordable housing that people are proud to own, and call home!

Recent Posts

This site is protected by