Operating instructions

48
operating modes. See Table 37 for a list of overrides. See the
Operating Modes section on page 68 for more information re-
garding operating modes.
Override #1: Cooler Freeze Protection
— This override at-
tempts to avoid the freeze protection alarm. If the Leaving
Water Temperature is less than Brine Freeze Set Point (Brine
Freeze Setpoint, LOSP) + 2.0° F (1.1º C) then a stage of
capacity is removed.
NOTE: The freeze set point is 34 F (1.1 C) for fresh water
systems (Cooler Fluid Type, FLUD=1). The freeze set point
is Brine Freeze Set Point (Brine Freeze Setpoint, LOSP), for
Medium Temperature Brine systems (Cooler Fluid Type,
FLUD=2).
Override #2: Circuit A Low Saturated Suction Temperature
in Cooling
Override #3: Circuit B Low Saturated Suction Temperature
in Cooling
Override #4: Circuit C Low Saturated Suction Temperature
in Cooling — These overrides attempt to avoid the low suction
temperature alarms and are active only when the compressor is
running beyond the fully unloaded level. The slide valve in the
affected circuit will be decreased in position if the Saturated
Suction Temperature is less than Brine Freeze Set Point (Brine
Freeze Setpoint, LOSP) –18.0 F (–10 C) for 90 seconds, or the
Saturated Suction Temperature is less than –4 F (–20 C).
Override #5: Low Temperature Cooling and High Tempera-
ture Heating — This override decreases capacity when the dif-
ference between the Control Point (Control Point, CTPT) and
the Leaving Water Temperature (Cooler Leaving Fluid, LWT)
reaches a predetermined limit and the rate of change of the wa-
ter is 0º F per minute or still decreasing.
Override #6: Low Temperature Cooling and High Temperature
Heating — This override decreases capacity (approximately
5% of circuit capacity) when the Entering Water Temperature
(Cooler Entering Fluid, EWT) is less than the Control Point
(Control Point, CTPT).
Override #7: Ramp Loading
— No capacity stage increase
will be made if the unit is configured for ramp loading (Ramp
Loading Select, RL.S=ENBL) and the difference between the
Leaving Water Temperature and the Control Point is greater
than 4º F (2.2º C) and the rate of change of the leaving water is
greater than Cool Ramp Loading Rate (Cooling Ramp Load-
ing, CRMP). Operating mode 5 (MD05) will be in effect.
Override #8: Service Manual Test Override
— This over-
ride mode places the unit into Service Test mode. The user can
then use Service Test functions to test the unit. All safeties and
higher priority overrides are monitored and acted upon.
Override # 9: Demand Limit
— This override mode is active
when a command to limit the capacity is received. If the
current unit capacity is greater than the active capacity limit
value, a stage is removed. If the current capacity is lower than
the capacity limit value, the control will not add a stage that
will result in the new capacity being greater then the capacity
limit value. Operating mode 4 (MD04) will be in effect.
Override #10: Cooler Interlock Override
— This override
prohibits compressor operation until the Cooler Interlock
(Cooler Flow Switch, LOCK) is closed.
Override #11: High Temperature Cooling and Low Temper-
ature Heating — This override algorithm runs once when the
unit is switched to ON. If the difference between the Leaving
Water Temperature (Cooler Leaving Fluid, LWT) and the
Control Point (Control Point, CTPT) exceeds a calculated
value and the rate of change of the water temperature is greater
than –0.1º F/min, a stage will be added.
Table 37 — Capacity Control Overrides
CAPACITY CONTROL OVERRIDES
1 Cooler Freeze Protection
2 Circuit A Low Saturated Suction Temperature in Cooling
3 Circuit B Low Saturated Suction Temperature in Cooling
4 Circuit C Low Saturated Suction Temperature in Cooling
5 Low Temperature Cooling and High Temperature Heating (LWT)
6 Low Temperature Cooling and High Temperature Heating (EWT)
7 Ramp Loading
8 Service Manual Test Override
9 Demand Limit
10 Cooler Interlock Override
11 High Temperature Cooling and Low Temperature Heating
12 High Temperature Cooling and Low Temperature Heating
(minimum load control in effect)
13 Minimum On/Off and Off/On Time Delay
14 Slow Change Override
15 System Manager Capacity Control
16 Circuit A High Pressure Override
17 Circuit B High Pressure Override
18 Circuit C High Pressure Override
19 Standby Mode
20 —
21 —
22 Minimum On Time Delay
23 Circuit A Low Saturated Suction Temperature in Cooling
24 Circuit B Low Saturated Suction Temperature in Cooling
25 Circuit C Low Saturated Suction Temperature in Cooling
26 Circuit A High Discharge Gas Override
27 Circuit B High Discharge Gas Override
28 Circuit C High Discharge Gas Override
29 —
30 —
31 —
32 —
33 —
34 Circuit A Low Refrigerant Charge
35 Circuit B Low Refrigerant Charge
36 Circuit C Low Refrigerant Charge
37 —
38 —
39 —
40 —
41 Circuit A High Current Override
42 Circuit B High Current Override
43 Circuit C High Current Override
44 Circuit A High Suction Superheat at Part Load
45 Circuit B High Suction Superheat at Part Load
46 Circuit C High Suction Superheat at Part Load
47 —
48 —
49 —
50
Circuit A MCHX MOP Control
51 Circuit B MCHX MOP Control
52 Circuit C MCHX MOP Control
53 Circuit A Delay for Unloading the Slide Valve
54 Circuit B Delay for Unloading the Slide Valve
55 Circuit C Delay for Unloading the Slide Valve
56 Circuit A Delay for Refrigeration Isolation Valve to Open
57 Circuit B Delay for Refrigeration Isolation Valve to Open
58 Circuit C Delay for Refrigeration Isolation Valve to Open
59 Circuit A Low Oil Level
60 Circuit B Low Oil Level
61 Circuit C Low Oil Level
62 Circuit A High Motor Temperature Override
63 Circuit B High Motor Temperature Override
64 Circuit C High Motor Temperature Override
77 Boostload Function