Heatcraft Refrigeration Products H-IM-79B - Manual (Page 17)

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Defrost
DEFROST TIMING
When power is first applied to the system, its timer starts counting time. If 4 defrost are
programmed, it will initiate a defrost every 6 hours from when power was first applied.
Beacon II does not have a real time clock. Beacon II does provide the ability to delay the
starting of the first defrost.
DEFROST DELAY START TIME
Example: The system is first powered up at 8:00 AM and is programmed for 4 defrost per
day. The user would like the first defrost at 10:00 AM. To accomplish this, use the
“PROGRAM REVIEW” button to scroll to dFS . Use the “SELECTOR” switch to select 2
hours delay start, then press “ENTER” . The 1 st defrost will now occur at 10:00 AM and
then a defrost will occur every 6 hours thereafter.
DEFROST SCHEDULE IN MEMORY
Beacon II does not have a real time clock but it keeps track of the time that has elapsed in
its memory. It also keeps in memory the number of defrosts scheduled and how much time
has elapsed between defrosts. If a power failure occurs, when power is restored Beacon II
remembers how many defrosts are scheduled and it remembers how much time was left
until the next defrost. It will then defrost based on this timing. So, if the power failure lasted
15 minutes, the defrost schedule will be off by 15 minutes.
RESETTING DEFROST SCHEDULE
When a power interruption causes a severe lag in the defrost schedule, the defrost
schedule can be reset in the following manner. First, press the reset time button on the
board to zero out the internal counters. Then, program the appropriate defrost delay start
time for the next desired defrost period. The defrost schedule will be correct until you have
another power outage.
ELECTRIC DEFROST MODE
When a defrost is initiated, the EEV closes, the compressor is allowed to pumpdown and
shut off. The evaporator fans are cycled off and the defrost heaters are energized.
On multiple evaporator systems, all controllers must terminate their defrost, either on
temperature or fail-safe time, before the master controller will end the defrost cycle.
Pumpdown / Defrost
Service Mode
A single pole, single throw switch (SPST) is supplied in each condensing unit for shutting
off the system. Closing the “Service” switch in the condensing unit will cause the system to
pumpdown and shut off. “Ser” will be displayed on the Beacon board LED and “SERVIC” is
displayed on the Smart Controller LCD display. The Evaporator Fan and Heaters will be de-
energized in the Service Mode.
The system will not restart until the SPST switch is
placed in the “NORMAL” or “OFF” position.
or
A remote “Service” switch can be added to the Beacon II board across the “Ser” and “C”
connections of the terminal block. It will operate in the same manner as the switch above.
or
The system can be pumped down by pressing the “SERVICE” button twice. To restart the
system, press the “CLEAR” button.
or
The system can be pumpdown for service by closing the Liquid line service valve in the
condensing unit, then closing the suction line service valve when the system trips on the
low pressure switch.
In order for air defrost evaporator fan motors to cycle off during “Service” mode, the fan
motors must be wired through the fan relay on the Beacon II board.