19
Table 14 — Part Load Data Percent Displacement, Standard Units
*Minimum Load Valve energized. Minimum load valve will only be
energized with decreasing capacity. Minimum load valve cannot be
enabled with digital compressor operation on 30MP020-045 units.
NOTE: The capacity steps listed for the 30MP055-071 may vary
from what is depicted due to the different size compressors used in
the circuit.
Ramp Loading — Ramp loading (Configuration
SLCT
CRMP) limits the rate of change of leaving fluid tem-
perature. If the unit is in a Cooling mode and configured for
Ramp Loading, the control makes 2 comparisons before decid-
ing to change stages of capacity. The control calculates a tem-
perature difference between the control point and leaving fluid
temperature. If the difference is greater than 4° F (2.2° C) and
the rate of change (°F or °C per minute) is more than the con-
figured Cooling Ramp Loading value (CRMP), the control
does not allow any changes to the current stage of capacity.
Low Entering Fluid Temperature Unloading
— When the
entering fluid temperature is below the control point, the
control will attempt to remove 25% of the current stages being
used. If exactly 25% cannot be removed, the control removes
an amount greater than 25% but no more than necessary. The
lowest stage will not be removed.
Minimum Load Control
— If equipped, the minimum load
control is energized only when one compressor is running on
the circuit and capacity is decreasing.
Cooler Freeze Protection
— The control will try to prevent
shutting the chiller down on a Cooler Freeze Protection alarm
by removing stages of capacity. If the cooler fluid selected
is Water, the freeze point is 34 F (1.1 C). If the cooler fluid
selected is Brine, the freeze point is the Brine Freeze Point (Set
Points
FRZ
BR.FZ). This alarm condition (A207) only
references leaving fluid temperature and NOT Brine Freeze
point. If the cooler leaving fluid temperature is less than the
freeze point plus 2.0° F (1.1° C), the control will immediately
remove one stage of capacity. This can be repeated once every
30 seconds.
Low Saturated Suction Protection
— The control will try to
prevent shutting a circuit down due to low saturated suction
conditions by removing stages of capacity. The circuit alert
condition (T116) compares saturated suction temperature to the
configured Brine Freeze Point (Set Points
FRZ
BR.FZ).
The Brine Freeze point is a user-configurable value that must
be left at 34 F (1.1 C) for fresh water systems. A lower value
may be entered for systems with brine solutions, but this value
should be set according to the freeze protection level of the
brine mixture. Failure to properly set this brine freeze point val-
ue may permanently damage the brazed plate heat exchanger.
The control will initiate Mode 7 (Circuit A) to indicate a
30MP UNIT SIZE
CONTROL STAGE
(Run StatusVIEWSTGE)
CAPACITY
(% Displacement)
WITHOUT MINIMUM LOAD VALVE
CAPACITY
(% Displacement)
WITH MINIMUM LOAD VALVE
015
1 50 50/18*
2 100 100
020
1 50 50/25*
2 100 100
030
1 50 50/34*
2 100 100
040
1 33 33/21*
267 67
3 100 100
045
1 33 33/22*
267 67
3 100 100
050
1 50 50/40*
2 100 100
055
1 44 44/35*
2 100 100
060
1 42 42/33*
2 100 100
065
1 38 38/31*
2 100 100
071
1 44 44/33*
2 100 100
47
46
45
44
43
42
41
0 200 400 600 800 1000
TIME (SECONDS)
2 STARTS
3 STARTS
DEADBAND EXAMPLE
LWT (F)
MODIFIED
DEADBAND
STANDARD
DEADBAND
8
7
6
5
LWT (C)
LEGEND
LWT — Leaving Water Temperature
Fig. 14 — Deadband Multiplier
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