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8.9
Holdback
Holdback can be used to prevent the program from running ahead of the actual heating or
cooling.
The Holdback value is the amount, in degrees, by which the Program Setpoint can run ahead
of the measured temperature before Holdback operates. The value applies to a whole
program.
To set the value press page
up
or down
to set.
Holdback can be used in Rate, Time, Step and Dwell segments.
• For Rate and Time segments Holdback will operate during the segment.
• For a Step segment Holdback delays continuation to the next segment until the step target
is reached.
• For a dwell segment Holdback delays the start of the programmed dwell time, until the
Target Setpoint of the previous segment is reached.
The Holdback Type can be set as follows:
• Low - Applies to heating only
• High - Applies to cooling only
• Band - Applies to both heating and cooling
• Off - Holdback is off
To set the Holdback type press page
Holdback Type for each segment and press up
The default setting for Holdback is Off.
If a holdback value has been set (see "Programming") and the program goes into a hold state,
the red HLD indicator will flash, until the measured temperature catches up.
If while in this condition the program itself is put into hold by pressing the RUN/HLD button, the
"HLD" indicator will stop flashing and remain on with the "RUN" indicator. When the program is
started again by pressing the "RUN/HLD" button, the "HLD" indicator will flash again if the
measured temperature has not caught up with the program.
8.10
Power failure recovery
If there is a power interruption to the controller during a program, when power is restored the
controller pauses the program, then ramps the measured temperature back up to the current
Program Setpoint (PSP) before continuing the program.
• Power fail during ramp segments: The ramp rate will be that of the current ramp segment.
• Power fail during Dwell segments: The ramp rate will be that of the previous ramp segment.
If a previous ramp segment does not exist, then the dwell will continue at the current
measured temperature.
• Power fail during Time-to-target segments: The ramp rate will be that of the current
segment. The ramp rate is maintained, but the time remaining is recalculated.
If there is a power interruption while controlling to Setpoint, when power is restored the
controller automatically calls for maximum power.
MF 55-GB 1.21
twice, press scroll
twice, then press scroll
until Holdback Value appears and press
until the display shows
or down
to set.
MRF 16/22
27
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