Future Design MCT-CM, User Manual

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MCT-CM
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minutes in order to activate defrost. Setting the field to zero allows the user to disable defrost operation for
testing purposes or to prevent it from operating if its use is not required.
The
Fan Delay field is used to adjust the fan delay. The time can be set from 0-999 seconds.
Pressing
Defrost while programmed for timed defrost will activate a single defrost cycle. If defrost is configured
for timed process, defrost will only activate if the OEM configured loop SP or monitor point PV is below the
enable set point that is entered in the MCT configurator.
9.1.1 Defrost Description of Operation
The defrost interval timer is activated when the OEM configured defrost enable output(s) are on for timed
defrost. In order for the interval timer to be activated when defrost is configured for timed process, the OEM
configured loop set point or monitor point value must also be below the enable set point. If at any time the
enable outputs are turned off, or the loop or monitor point rises above the enable set point, the interval timer
will be reset.
NOTE: When a loop is selected as the enable point, the loop set point must be equal to or below the defrost
enable set point. When a monitor point is selected as the enable point, the process value must be
equal to or below the defrost enable set point.
Once the user set interval has elapsed, the defrost cycle begins. When the defrost cycle starts, the OEM
configured output defeats will be activated. This will turn off all outputs configured for defeat regardless of any
other settings. If a digital output is configured as a Defrost Output, the output will be turned on for the duration
of the defrost cycle. Once the user set defrost duration has elapsed, the defrost cycle will be terminated and
the fan delay will be activated.
During the fan delay period, the defrost output defeats are removed and the OEM configured precool output
defeats are activated. If a digital output is configured as a Defrost Precool Output, the output will be turned on
for the fan delay period. Once the fan delay period has expired, the precool output defeats are removed allowing
all outputs to return to normal function.
The system will continue to run normally until the interval timer elapses once more, and the cycle begins again.
If at any time the user presses the Demand Defrost button, the interval timer will be reset and a single defrost
cycle will be initiated. Note that if defrost is configured for timed process, pressing the Demand Defrost button
will only initiate a defrost cycle if the OEM configured loop or monitor point is also below the enable set point
that is entered in the MCT configurator.
NOTE: If redundant systems are also configured, consult the following section 9.2 Redundancy for additional
information on defrost operation in conjunction with redundant system operation.
9.2 Redundancy
The MCT can be configured by the OEM to operate redundant systems.
These ‘systems’ could be pump
stations, refrigeration units, etc. This feature would be typically used when two identical systems share a
common process and the failure of one system would turn on the back-up system so that the process can
continue operation with interruption. The MCT allows the systems to be configured for alternate or concurrent
modes
operation. Alternate and concurrent mode operation both provide “equal” run time switching for each
system when a redundancy alarm (high/low alarm, system failure) does not exist.