Are you thinking about adding a central air conditioner to your home? Or maybe you’re ready to upgrade your current central air? If so, it’s wise to think ahead and ask what adding or upgrading means in terms of compatibility with your current furnace. The answer can depend on a number of factors. Let’s start with the basics and work our way to the more complex.
Standard HVAC Components
If you’re thinking about installing a standard, or conventional, air conditioner, then pairing with your existing furnace likely won’t be an issue. But there are a few things to consider. You’ll want to confirm that the indoor coil will fit in the space above your furnace and that the furnace has enough blower power for the AC—that is, that it can move enough air with enough pressure for effective cooling. In most cases, your control wiring should not be an issue, but is definitely something to check out. Your local HVAC pro can help you address the details.
Staged or Variable Speed AC
If you’re considering staged or variable speed/modulating AC, there are additional considerations in regard to pairing equipment. In fact, it may be critical to match the AC to the furnace. Many of the newer AC units have “communicating” controls that require both a compatible furnace and a special thermostat for communication between system components and for blower control. It's very important in air conditioning to have the right amount of airflow—either too much or too little can cause problems. When the AC is operating in low speed, the furnace must be able to automatically shift to a corresponding airflow—and that’s where appropriate communication between AC and furnace is critical.
Matching Brands and Products
Because the communication between components is so important if you’re installing staged or variable speed/modulating AC, it’s usually best to have both your furnace and AC manufactured by the same company—a Carrier furnace and a Carrier AC, for example. This will assure that the furnace will be able to match the airflow needs of the air conditioner.
In some cases—usually higher end, higher efficiency systems—it may even be necessary to pair specific products within the same brand. For example, a Carrier Infinity series AC must be paired with a Carrier Infinity or Performance furnace—it will not work with a Carrier Comfort series furnace.
What About Replacing My Furnace at the Same Time?
It’s logical for homeowners to wonder if it isn’t worth it to replace their furnace at the same time as they’re installing or replacing their air conditioning. If you want to upgrade to staging or modulating AC, then you may have to replace your furnace for the communication reasons noted above. But that may not be the only reason to consider replacement. If your furnace is over 14 years old, you can gain significant efficiency with a new unit. In fact, that may be the case even if your furnace is only 10 or 12 years old.
Your best bet is to contact your local HVAC pro and schedule an appointment to discuss the options you have and what will best fit your needs and budget.