Replacing Coils vs. Entire Unit

June 2, 2008
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Do I replace the coils or the entire unit? This is a question faced by unit owners and contractors all too often. When a system has been operating correctly and only the coils have failed, when is it justifiable to repair the system versus replacing the entire system? The answer depends on the situation and sometimes the situation may not be strictly mechanical.

An example of the latter is if the coils have been stolen. If the unit is over 20 years old, it will probably be best to replace the entire unit. Theft is most usually covered by the owner’s insurance. If it is a relatively newer system, the insurance company may only pay for the repair, which will require replacement coils.

If the coils have been vandalized or hail-damaged, a decision is subject to the insurance company. Depending upon the severity of the damage, it may be possible to straighten the fins and achieve the required capacity.

If fins have degraded to the point of impaction and restricted the airflow, you should first determine the cause of the corrosion. Was it salt air, chemical reaction, normal degradation, or something else? Without first determining the cause, replacement coils will in all likelihood fail prematurely as well. If the unit is in relatively good condition, this is a good candidate for a coil replacement.

If the coil copper tubing has become perforated in a refrigeration system, acid is the only cause. Clean and neutralize the refrigerant loop piping and replace the coils. And be aware that in all likelihood, the compressor will soon fail as well.

If the coil tubing bursts due to over-pressurization, then you have another good candidate for a coil replacement.

Another candidate for coil replacement is a situation in which fins are impacted with filth and cannot be cleaned.

OEM COILS?

The next common question is: Do I have to use OEM coils?

The simple answer is no. Other than a piece of pipe, the coils are the dumbest components in the system. All reputable coil manufacturers utilize a coil capacity program to verify the required capacity of coils they manufacture. If you provide the system parameters to these manufacturers, they will engineer a replacement coil with the same footprint as the OEM coil that will perform as required.

Now, there has been a trend with some of the major OEMs to reduce the thickness of the fin material as well as the tube wall to reduce manufacturing costs. With a coil, it’s very simple: Greater material thickness will result in a longer lasting coil. Companies that specialize in replacement coils recognize this and can provide you with a replacement coil built to the old standard of durability.

BUILT TO LAST?

And finally: How do I know if the coils are built to last? One needs to look for certain standards of construction:

Fin Thickness
0.006 minimum to 0.010

Tube Wall Thickness
3/8”: 0.014 minimum;
1/2”: 0.016 minimum;
5/8”: 0.020 minimum

Casing
G-90 Galvanized, minimum 20 gauge

Publication date: 06/02/2008

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