The Matched Coil Is Critical

May 22, 2006
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When it comes to higher-efficiency unitary products, is coil matching as critical as it has been in the past? The answer is an unqualified yes!

When it comes to coil matching, don't cut corners. If a replacement air conditioner or heat pump needs to be installed, it's as important as ever to make sure the indoor coil and outdoor coil are matched. You can't leave the old indoor coil and install a new outdoor unit; performance and longevity will suffer.

In some cases, the new air conditioning system your company is installing will be larger than the old one, and that goes for the indoor coil as well. How you find room for the new indoor coil may require a little extra thought, but with proper planning and customer communication, it can be done, as we explained in earlier Tech Tips.

The most crucial thing is to explain the importance of the matched coil to your customers. You might draw an analogy to clothing: If someone is buying a larger suit, what are the chances that all he or she needs is a new jacket? Zero to none. If the top no longer fits, neither does the bottom. The matched suit is the customer's best option. Likewise, matched indoor and outdoor coils are the best choice - but the long-term ramifications could be much more costly for not matching this outfit.

The Airflow Connection

One of the largest issues affecting system operation is inadequate airflow on the indoor side. But will your customers understand that coils are involved with air?

Probably not. They can visualize refrigerant moving inside the coils, but may not immediately imagine the air moving around them. Chances are, you will need to spell it out. Coil surfaces exchange heat at different points of the system. Air moving around those coils gives its heat to the refrigerant in the coils, and the refrigerant carries it away. This is how the customer's home is cooled.

If there isn't enough air circulating around those indoor coils, the system won't exchange enough heat to the refrigerant, through the coils. There can be many causes for this, including having an indoor coil that is not matched with the rest of the system, or a poorly designed duct system. In addition to comfort concerns, it can cause operational problems.

During heat pump heating operation, correct airflow is especially critical. If the airflow is not correct, it skews the refrigeration system's operation, and this will have an adverse effect on the refrigeration side. It may look like a refrigerant problem, but it's really an airflow problem.

Dealing With It

The first thing to do is make sure your employees understand the ramifications of not matching the coils. It's almost instinctive for them to want to do their best by the customer, so they may want to give them the cheapest solution for their replacement needs. In this case, however, the cheapest solution is not the most cost effective.

Another consideration is time. Changing the indoor coil, as we have mentioned in earlier Tech Tips, may involve freeing up more space for those coils. This is especially true for indoor coils that were installed in a closet or attic. In order to make sure airflow is adequate, enough air must be able to circulate around those coils. Some new framing might be needed in the space, or an electrician might need to be called in, depending on your local codes.

This amount of time might look rather daunting for contractors installing replacement systems during the busy cooling season. You might want to have some repaired window units on hand to keep customers comfortable while the work is completed. Or, you might schedule it so that you can go back and put in a matched coil later, when it's not so busy; but don't wait too long. Make sure you have a good follow-up system in place to make sure these customers don't fall through the cracks.

For more information, click on the Emerson Climate Technologies logo above.

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