Right Ways To Defrost Evaporators

March 31, 2005
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A common refrigeration equipment service problem occurs when an evaporator or its drain pan becomes completely engulfed in ice, and the technician needs to de-ice them. Normally this is a relatively easy but time-consuming task. However, the tech needs to be patient; it can become a nightmare if care is not taken.

Never use an ice pick, screwdriver, or similar device to remove ice from a coil. This is just asking for serious trouble. It doesn't take much force to puncture one or more of the tubes within an evaporator, and the relatively simple repair turns into a major one. The technician now has to repair the original problem as well as repair the puncture in the evaporator if possible; sometimes the entire evaporator must be replaced.

This is definitely not a situation a technician wants to present to his manager or to the customer.

Using an open flame or torch to de-ice a coil is likewise not good practice. This method is very unsafe and could cause damage to surrounding components, such as any electrical wiring or plastic housing.

Better Options

If the system has a defrost cycle, such as those found in a freezer, the technician can simply initiate one or more defrost cycles. If the defrost system is working, it will defrost the evaporator, but will take time.

Another similar option is to shut down the refrigeration system and leave the evaporator fan running. This will also defrost the evaporator, but it's a rather slow process.

Many times, however, either the defrost system is not working properly or the technician doesn't have the time to wait for the system's defrost cycle (or evaporator fan) to de-ice the coil. In these cases the technician will need to manually de-ice the coil - the right way.

A quick method for manually de-icing an evaporator and its drain pan is to use water. Water is an excellent heat source. It can de-ice an evaporator rather quickly and efficiently. However, it is not always practical and many times it cannot be used.

In order to use water, there must be a means to drain both the melted ice and the added water away without causing damage to any product or to the building structure. If this is not possible, water cannot be used.

A heat gun offers a very efficient means of defrosting a coil without using water. A heat gun provides a sufficient amount of controlled heat, enabling a technician to safely defrost a coil and drain pan.

The tech then only needs to be concerned about water run-off from the melted ice, which still could present a problem. The technician may need to catch or drain the water runoff with a bucket or shop vacuum before it can cause any damage. It's best to try to de-ice the drain line first so the remaining water can be carried away through the system's own drain line.

Whatever method a technician uses for system de-icing, patience is a must. Without it, a technician can easily make a serious mistake and cost his company and the owner of the equipment an unnecessary expense.

Joe Marchese is owner of Coldtronics, Pittsburgh. He can be reached at 412-734-4433, www.coldtronics.com, or joe@rhvactools.com.

Publication date: 04/04/2005

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