Considerations for Using Anti-Sweat Heaters in Refrigerated Food Merchandisers

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Anti-Sweat Heaters installed in food display merchandiser equipment are designed to heat surfaces at external locations where the case surface temperature may be lower than the ambient air Dew-point; in so doing, they prevent moisture from condensing on that surface.

A typical supermarket merchandiser is designed, to operate in ambient air conditions of 75°F Dry Bulb (DB) and 55% Relative Humidity (RH) or lower. This yields a Dew-Point of 58°F. If the surface of the case drops below 58°F), moisture in the air can condense on that surface. Hence, anti-sweat heaters are installed to keep case surface temperatures above the Dew-point.

Note: Moisture on any surface is never a good thing. This moisture can cause premature oxidation of the surface in the form of rust, and/or loss of paint luster as well as a place for mold or mildew to form, and, if it winds up on the floor, it is now a trip hazard. Plus, few consumers like handling food products that are wet.

The anti-sweat heater that is predominately used in most merchandisers is a design that uses a simple wire with an electric current passed through it; the current generates heat. Generally, the wire is attached to a thin piece of aluminum foil (other materials could be used) or it is wrapped with a cloth.. These heaters are sometimes referred to as ‘mullion heaters’ or ‘strip heaters’. They are also used on or in, glass or solid doors to prevent the formation of condensation on the inside and outside surfaces of the display doors, frames and mullions.

The anti-sweat heater is a resistive load typically requiring 120 AC voltage and will vary in amperage depending on manufacturer, merchandiser design, and application.

Figure 1:  Typical power (watts) draw per case design

Case Design	Watt Range	Watt Range w/doors
12 ft. Single Depth Coffin	120 – 160 w	48 – 72 w
12ft. Back to Back Coffin	312 – 480 w	218 – 285 w
12 ft. Multi Deck Low Temp	270 – 450 w	—
Glass Doors Reach-In Low Temperature (per door)	100 – 140 w	—
Glass Doors Reach-In Medium Temperature (per door)	24 – 40 w	—
12 ft. Service Case for Meat/Deli	179 – 240 w	—

Anti-Sweat Heaters installed in food display merchandiser equipment are designed to heat surfaces at external locations where the case surface temperature may be lower than the ambient air Dew-point; in so doing, they prevent moisture from condensing on that surface.

A typical supermarket merchandiser is designed, to operate in ambient air conditions of 75°F Dry Bulb (DB) and 55% Relative Humidity (RH) or lower. This yields a Dew-Point of 58°F. If the surface of the case drops below 58°F), moisture in the air can condense on that surface. Hence, anti-sweat heaters are installed to keep case surface temperatures above the Dew-point.

Note: Moisture on any surface is never a good thing. This moisture can cause premature oxidation of the surface in the form of rust, and/or loss of paint luster as well as a place for mold or mildew to form, and, if it winds up on the floor, it is now a trip hazard. Plus, few consumers like handling food products that are wet.

The anti-sweat heater that is predominately used in most merchandisers is a design that uses a simple wire with an electric current passed through it; the current generates heat. Generally, the wire is attached to a thin piece of aluminum foil (other materials could be used) or it is wrapped with a cloth.. These heaters are sometimes referred to as ‘mullion heaters’ or ‘strip heaters’. They are also used on or in, glass or solid doors to prevent the formation of condensation on the inside and outside surfaces of the display doors, frames and mullions.

The anti-sweat heater is a resistive load typically requiring 120 AC voltage and will vary in amperage depending on manufacturer, merchandiser design, and application.

It is the storeowner’s responsibility to be cautious when turning the HVAC system thermostat up in the summer or down in the winter to “save energy”. It is possible that these supposed savings will generate more electrical usage by the anti-sweat heaters or may cause external surfaces of food merchandisers to condense moisture. Remember, the performance of the merchandisers is based on a DB temperature of 75° F and an RH of 55%; even when the store is closed!.

For more complete information, go to the ACCA website and download the Technical Bulletin “An Overview on the Types and Functions of Anti-Sweat Heaters Used in Refrigerated Food Merchandizers.”

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Posted In: ACCA Now, Technical Tips