Defrosting • 15
DEFROSTING
General
Periodic defrosting to keep the coil free of frost is accomplished automatically by a time clock used in conjunction with an electric or hot gas
defrost. For best results, temperature termination of defrost is strongly recommended on Zero Zone cases.
Defrost Settings and Controls
ELECTRIC DEFROST
Frequency: One defrost per day is recommended. Time of day: Avoid defrosting during periods of heavy shopping or stocking. Drip Time:
Electric defrost does not require any drip time because Zero Zone provides a built-in fan delay thermostat.
Electric Defrost Fail-safe Times:
FROZEN FOOD
ICE CREAM
1/Day at 55 Minutes
1/Day at 55 Minutes
At ASHRAE test conditions and 208 volt defrost heater operation, the typical observed defrost durations are 30 minutes for frozen food and 40
minutes for ice cream.
Preferred Termination: For optimal performance, Zero Zone recommends a temperature-terminated defrost, using a defrost termination
thermostat or probe sensing the coil temperature. The case has the probe located at the center of the coil in the center of the bottom row of
tubes. If the case is so equipped, the defrost termination temperature is 50°F. Zero Zone provides a defrost termination thermostat unless a
control system defrost probe is requested.
Temperature termination based on coil temperature allows the length of defrost to vary depending on how much frost is on the coil and the
defrost heater voltage. Coil frost is a function of shopping patterns, stocking habits, general door maintenance and ambient temperature and
humidity. More frost requires a longer defrost. A lower defrost heater voltage extends the defrost duration.
Alternate Termination: If it is not possible to terminate the defrost cycle based on a defrost termination thermostat or probe sensing the
temperature at the coil, and the only available temperature probe is sensing the discharge air temperature, then the termination temperature
should be set to 65°F, zero minutes drip time.
Zero Zone electric defrost freezers are delivered with the defrost thermostat open-on-rise contacts wired in series with the defrost heaters.
Unless the installer rewires the defrost thermostat, the defrost heater is de-energized when defrosting is complete.
Electric defrost freezer is equipped with a high-limit, snap-disc thermostat that de-energizes the defrost heater if the coil temperature exceeds
85°F to provide a secondary safety termination.
HOT GAS DEFROST
Frequency: One hot gas defrost per day is recommended. Time of day: Nighttime defrosting is preferred to avoid periods of heavy shopping or
stocking. Drip time: Hot gas defrost requires a 5 minute drip time.
Hot Gas Defrost Fail-safe Times:
FROZEN FOOD
ICE CREAM
Hot Gas
1/Day at 30 Minutes 5 Minute Drip
1/Day at 30 Minutes 5 Minute Drip
Reduced Temp Hot Gas
1/Day at 40 Minutes 5 Minute Drip
1/Day at 40 Minutes 5 Minute Drip
Summary of Contents for CRYSTAL MERCHANDISER
Page 25: ...Illustrations Case Squareness 23 Illustrations Figure 6 Case Squareness Refer back to page 5...
Page 26: ...24 Illustrations Shim Placement Illustrations Figure 7 Shim Placement Refer back to page 5...
Page 27: ...Illustrations Shim Orientation 25 Illustrations Figure 8 Shim Orientation Refer back to page 5...
Page 29: ...Illustrations Spacer Block 27 Illustrations Figure 10 Spacer Block Refer back to page 6...
Page 34: ...32 Illustrations Drain Line Illustrations Figure 15 Drain Line Refer back to page 7...
Page 38: ...36 Illustrations Electrical Box Illustrations Figure 19 Electrical Box Refer back to page 11...
