Getting the Right Coils

To an extent, every HVAC installation is a custom installation. We use off the shelf parts, but the exact configuration is always going to depend on the installation site and the end user. The budget, electrical connections, desired efficiency, and so much more all decide what the end system will be. Every part has a role to play, and any mismatched parts will cause problems across the system.


Matching Your Coils

Your evaporator and condenser coils need to match. Every coil has a different set of ratings, different capacities, and different applications. You couldn’t use a condenser coil from a residential unit in an industrial system. Sure, we can make it fit with a ton of adapters, but the pressures and flow rates would probably make it blow up. The same issues exist at all scales, but with varying consequences.


Why Wouldn’t They Match?

Your contractor will examine your facility and determine the appropriate rating. You might need a four, five, or even ten ton unit. That all depends on the circumstances of the installation. This is also where contractors and manufacturers disagree about how a cooling system should be designed. This disagreement can lead to significant consequences for your business.

The official position of most, if not all manufacturers is that coils need to match. If your facility needs a 5 ton condenser, then it needs a 5 ton evaporator. The numbers need to match across the board. Their explanation is that the only way to get maximum efficiency is for the capacity of the coils to be the same. In all other circumstances, one coil will work harder than the other to keep up with the load. Ultimately, this will tax the system and lead to extended running times.

Some contractors will mismatch the coils to alter the system’s performance. There is some belief that certain combinations will yield better performance, better dehumidification, or better efficiency. There is some evidence that this may be the case. Simulation programs used to assist in designing HVAC systems can demonstrate the altered performance, but will not cover the impact on the hardware lifetime or fully cover all the effects.


Accidental Mismatches

During repairs, coils may also be easily mismatched. The evaporator coil may fail, but at least the condenser is still working. Your repair technician comes in, unloads a ‘matching’ coil from the truck, the system fires up an hour later, and all is well. Unfortunately, there are some complications here. The $600 repair bill may be a cancer, waiting to bring you more bills in the months to come.

The HVAC Industry isn’t stagnant. There are new things coming out all the time, new designs and better systems. That fifteen year old evaporator coil may be rated at 5 tons, but its other capacities and efficiencies will be different. Perhaps your Thermal Expansion Valve won’t quite match up to it anymore or some art of the system won’t fall in-spec. with the new part.

To an extent, we can see this problem in every industry. New technology means that while we can make two things fit together, we shouldn’t necessarily do that. We can fit a Blu Ray disc in a CD Player, but we’re not going to hear anything coherent. It is often recommended to replace both the Condenser and Evaporator coil at the same time to avoid this issue. Truth be told, if one coil has failed, the other can’t be far behind anyway.



As an end-user, contractors and small business owners are free to do as they wish with their system designs. If they want to buy an odd part, all the power to them, but there are some consequences for these actions. Outside the less predictable nature of these HVAC Installations, manufacturers will not provide warranty coverage to any system with mismatched parts or parts not specifically approved to work together.

This is a standard practice in near every industry. Products are designed with a specific application in mind. We build an engine to produce a specific horsepower and perform a certain way on the road. Using that engine for a tractor pull, at redline, is going to void the warranty. Manufacturers design and test their systems for particular setups, matching ones. Outside the performance and efficiency impacts, these odd configurations risk your warranty.



As always, we welcome your feedback and suggestions. Let us know what you want us to cover next.


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