Zero Zone RVZC30, Installation And Operation Manual

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RVZC30 (and BB/T/TBB/WA), RVZP30 (and BB/T/TBB/WA), RVC24
27
0407
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 mainte-
nance and ambient temperature and humidity. More frost
requires a longer defrost. A lower defrost heater voltage
extends the defrost period.
Alternate Termination: If it is not possible to terminate the de-
frost cycle based on a defrost termination thermostat or probe
sensing the temperature at the coil, and the only available tem-
perature probe is sensing the discharge air temperature, then
the termination temperature should be set to 65°F, zero min-
utes drip time.
Zero Zone electric defrost freezers are delivered with the de-
frost thermostat open-on-rise contacts wired in series with the
defrost heaters. Unless the installer rewires the defrost thermo-
stat, the defrost heater is de-energized when defrosting is com-
plete.
Zero Zone VZ and VZT 30” door electric defrost freezers are
also equipped with a high-limit, snap-disc thermostat that de-
energizes the defrost heater if the coil temperature exceeds
80°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 shopping or stocking.
Duration:
Hot gas defrost requires a 5 minute drip time.
Hot Gas Defrost Fail-safe Times:
Ice Cream Frozen Food
Hot Gas 1/day at 30 minutes 1/day at 30 minutes
5 minute drip 5 minute drip
Reduced 1/day at 40 minutes 1/day at 40 minutes
Temperature 5 minute drip 5 minute drip
Gas
Preferred Termination: For optimal performance, Zero Zone
recommends a temperature-terminated defrost, using a defrost
termination thermostat or probe attached to the dump line.
At ASHRAE test conditions, termination ranges from 12-22
minutes.
If the cases are so equipped, the defrost termination is 65°F.
Zero Zone provides a defrost termination thermostat unless a
control system defrost probe is requested.
DEFROSTING
General
Periodic defrosting to keep the coil free of frost is accom-
plished 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 electric defrost per day is recommended.
Time of day: Nighttime defrosting is preferred to avoid periods
of shopping or stocking.
Duration:
Electric defrost does not require any drip time because Zero
Zone provides a built-in fan delay thermostat.
Electric defrost Fail-safe Times:
Ice Cream Frozen Food
VZ 30” door 1/day at 45 minutes 1/day at 45 minutes
VZT 30” door 1/day at 55 minutes 1/day at 55 minutes
VZ 24” door & 1/day at 54 minutes 1/day at 54 minutes
WA, WB
At ASHRAE test conditions and 208 volt defrost heater opera-
tion, the typical observed VZ 30” door defrost durations are 28
minutes for ice cream and 19 minutes for frozen food. At the
same conditions, the typical observed VZT 30” door defrost
durations are 39 minutes for ice cream and 26 minutes for
frozen food. VZ 24” and WA and WB defrost durations are 43
minutes.
Preferred Termination: For optimal performance, Zero Zone
recommends a temperature-terminated defrost, using a defrost
termination thermostat or probe sensing the coil temperature.
The VZ and VZT 30” door case has the probe located at the
right hand side of the coil in the center of the bottom row of
tubes.
The VZ 24” door and WA and WB case has the probe located
at the right hand side of the coil in the top row of tubes.
If the case is so equipped, the defrost termination tempera-
ture is 50°F. Zero Zone provides a defrost termination ther-
mostat unless a control system defrost probe is requested.