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What is Condensation?

Condensation is the fog that suddenly appears in cold weather on the glass of merchandisers. Often times it blocks out the view of product, drips on the floor, freezes on the doors ...it's annoying. It's natural to blame the unit ...but you shoudn't jump to conclusions....

What Causes Condensation In Refrigeration Equipment?

Glass door condensation is the result of excess humidity in your building. The glass only provides a cold surface on which humidity can visibly condense. The fog on your glass is a form of condensation; so is the water that forms on the outside of a glass of iced tea in the summer and on the bathroom mirrors and walls after someone takes a hot shower. Condensation usually occurs first on the doors because glass surfaces have the lowest temperature of any of the interior surfaces of the building. When the warm moist air comes into contact with the cooler glass surfaces, the moisture condenses.

The important thing to recognize is this; your foggy glass and excessive flooding is trying to tell you something. It is important to reduce indoor humidity before it causes hidden, costly problems elsewhere. Problems like peeling paint, rotting wood, buckling floors, insulation deterioration, mildew, even moisture spots on ceilings and walls.

*FOGGY GLASS ON MERCHANDISERS IS A WARNING SIGN THAT HUMIDITY COULD BE DAMAGING YOUR UNIT

How Can My Unit Have Indoor Humidity?

Humidity is water vapor, or moisture, in the air. All air contains a certain amount of moisture, even indoors.

Where Does the Moisture Come From?

*MORE WATER VAPOR IN THE AIR MEANS A HIGHER INDOOR HUMIDITY. HIGH INDOOR HUMIDITY = CONDENSATION

How Does Humidity Effect Refrigeration Equipment?

I have had customers complain about condensation build up on their merchandiser and thought it may be time to blog some information regarding these concerns. For starters, all refrigeration equipment can and is immediately effected by its working environment.

Typically, the complaint of condensation comes from customers who do not have air condition facilities and are trying to utilize refrigeration equipment in less than desirable environments. (green house, in direct sun light, in garages, barns, etc.) I remind people constantly; be wary of the environment you plan to have you refrigeration equipment operate.

*IF OBJECTIONABLE CONDENSATION OCCURS ON THE INSIDE SURFACE OF THE GLASS OF YOUR UNIT, THE HUMIDITY LEVEL IS TOO HIGH.

To avoid excessive condensation, the following humidities are recommended in the equipment's environment:

Outside Temperature Inside Relative Humidity
-20°F 15 to 20%
-10°F 15 to 20%
0°F 20 to 25%
+10°F 25 to 30%
+20°F 30 to 35%

Will Reducing The Humidity In Our Environment Help Control Condensation?

Yes, by eliminating excessive humidity, you will eliminate most ...possibly all ...of the condensation...

How Can I Release The Humidity In Our Environment?

First and foremost we must control the sources of moisture while increasing ventilation. For example, an air conditioned facility will help tremendously. In fact, most manufacturers include the statement in the owner’s manual that reads: “this unit is to be placed in an air conditioned facility maintained at 75* F or cooler.” If air conditioning is absolutely impossible, I recommend a de-humidifier to be placed near the merchandiser. I also strongly recommend and encourage exhaust fans to remove excessive heat and to maintain a “fresh” air flow. Please keep in mind; refrigeration is the science of making cold air by removing heat (super heat). If we are unable to remove the heat from a refrigeration system into its environment, the refrigeration components will strain under the abnormal stress, boil the oil in the compressor, and thus loose its ability to lubricate properly.

Avoid environments where there is watering such as green houses, barns, garages, slaughter houses, etc. The addition of moisture increases humidity levels.

Opening the windows in the facility for a brief time each day (mornings) will go far toward allowing humid air to escape and drier air to enter. Heat loss will be minimal in the winter. Installation of storm windows will often relieve condensation on the prime windows by keeping the interior glass warmer.

Does Condensation Occur More Often In Particular Climates?

Absolutely! Condensation is more apt to occur in climates where the average January temperature is 35°F or colder because there will be greater extremes between indoor and outdoor temperatures affecting the glass (window or door) surfaces.

DURING THE SUMMER AND FALL, ALL PARTS OF A BUILDING PICK UP MOISTURE FROM DAMP AIR. IN THE FALL, WHEN THE WINDOWS ARE CLOSED AND HEAT IS TURNED ON, THIS MOISTURE WILL PASS INTO THE AIR OF THE BUILDING AND FOR A WEEK OR TWO THERE IS LIKELY TO BE CONDENSATION.

During the first year after construction or remodeling, it is likely a structure will have more condensation present because of the massive amount of moisture in the building materials themselves. Building materials need about one year to dry out, so excessive condensation can be expected in the first heating season. Even after the first year, if the humidity level is too high, condensation may still be a problem because today's structures are much "tighter" (in the interests of energy efficiency) than older buildings. Unfortunately, some of these newer materials and techniques used in newer construction such as; weather-stripping, insulation, vapor barriers, etc., are intended to keep out cold air ultimately lock moisture inside. As a result, moisture created by wash areas, restrooms, kitchens, laundries and occupants no longer flows to the outside as they should. Additional mechanical ventilation is needed and required.

Are There Cases Where Glass Condensation Is Only Temporary?

Yes, there are primarily three.

  1. New construction or remodeling
  2. The beginning of each heating season
  3. Quick changes in temperature

Wood, plaster, cement, and other building materials used in new construction and remodeling produce a great deal of moisture. During the heating season, there may be a certain amount of temporary condensation. During the humid summer months, structures will have absorbed some moisture. After the first few weeks of heating it will dry out, and you'll have fewer condensation troubles.

Sharp, quick drops in temperature can also create temporary condensation problems during the heating season.

Why, If My Old Unit Did Not Have Condensation Issues Does My New Unit Have It Now?

One of the reasons you probably replaced your old unit was because of its inefficiency. The old unit may have had bad door gaskets, poor seals, and was drafty. Those slight leaks allow the excessive humidity within your building to effect the unit. Now that your newer unit is tightly sealed, that excess humidity that is in your building is unable to escape, and therefore, it is showing itself on the glass. This is your first indication that you have too much humidity in your building. Most people think the problem is with the unit when in fact it is the environment the unit is placed in.

You Said I Should Have Less Humidity; But I Have Been Told That More Humidity is Healthier

At one time it was believed that humidifiers helped people stay healthy during the winter months. Recent tests have shown that for usually healthy people, this is not the case. In fact, humidifiers may actually cause health problems.

Does The Amount of Condensation Depend on The Type Of The Unit?

Sometimes.

Most glass door merchandisers now-a-days are triple pane insulated for energy efficiency and to increase heat deflection. Open case merchandisers for example, do not have doors and are “open to the air” so they may condensate for other reasons….

Besides High Humidity Levels, What Else Can Cause/Create Condensation?

As mentioned earlier; a ripped or torn door gasket can create massive amounts of condensation. I have witnessed bad door hinges that prevent the door from closing properly which has allowed air escape and massive amounts of condensation.

Hands down, the largest contributor of excessive condensation is the lack of maintenance. A dirty condenser is a major contributor of condensation. I have also witnessed units with food particles and such plugging the evaporator drain tube. This will cause a backup (dam like) of water in the evaporator area that can freeze, expand, melt, and create major condensation issue. Another common troublesome area may the temperature control. Often times when the temperature control fails, it fails in the continuously open position. This makes the compressor run constantly as it attempts to make “colder”. The compressor works triple time never shutting off and thus creates massive amounts of condensation.