Future Design MCT-CM, Руководство пользователя

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MCT-CM
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9.1 Defrost
The MCT defrost function was designed for use with refrigeration or other types of cooling systems that may
accumulate ice on cooling surfaces such as finned coils, and provide a means of pausing operation at preset
intervals in order to remove the build-up of ice to restore efficient operation.
NOTE: While the defrost function was intended for refrigeration systems, it may also be used as an interval
timer to perform a specific operation at preset intervals. Consult you OEM configuration regarding
the use and operation of defrost.
Defrost cycles are intended to keep ice from accumulating excessively on an evaporator coil. Ice accumulation
reduces the capacity of the refrigeration system and lowers the evaporator coil’s operating temperature. This
causes more ice to form and if not controlled, allows liquid refrigerant to flow back to the compressor which can
cause permanent damage and failure of the compressor. The control of ice accumulation is the primary function
of the defrost operation.
The second goal is to minimize excess use of energy from too frequent defrost cycles. The heat put into the
system during the defrost operation must be removed by the refrigeration system to bring the system back to
its operating temperature. The shortest defrost period and the minimum number of defrost cycles provides the
most efficient operation. These goals are accomplished by the proper setting of the first two parameters (defrost
interval and defrost duration).
The third goal is to minimize the increase in temperature during and after the defrost cycle. This is controlled
by the fan delay. The fan delay feature allows the refrigeration system to pre-cool the cooling coil before the
fan is turned on after a defrost cycle. This is adjusted to give a minimum amount of temperature rise after the
defrost cycle has completed.
The defrost settings allow the user to set the interval, duration and fan delay time for timed defrost sequences.
If the MCT is configured for timed defrost only, defrost cycles will take place at the interval set by the user. If
the defrost function is configured for ‘timed process’, the defrost interval for defrost will only be active when the
OEM configured loop or monitor point is below the defrost enable set point that is entered in the MCT
configurator. Consult your OEM configuration for the defrost type your system uses.
The
Status field displays the current status of defrost operation; Inactive, Active or Fan Delay Active.
The defrost
Interval field is used to set the defrost interval. The time can be entered in hours from 0-
999. If ‘0’
is entered for the defrost interval, defrost will not be initiated automatically. The defrost interval must be set
from 1-999 hours to activate defrost. Setting the field to zero allows the user to disable automatic defrost
operation for testing purposes or to require manual activation only via the demand ‘Defrost’ button.
The defrost
Duration field is used to set the defrost duration. The time can be entered in minutes from 0-999.
If ‘0’ is entered for the defrost duration, defrost will not operate. The defrost duration must be set from 1-999