135
Operating Modes —
Operating Modes are capacity
overrides that override the normal operation of the unit control.
See Table 62.
D.OIL
(Digital Oil Recover Mode) — When this mode is
active (
Operating Modes
o
MODE
o
D.OIL=
YES
) the unit is
ON and the digital compressor has been operating at less than
the standard Maximum A1 Unload Time (
Configura-
tion
o
UNIT
o
MAX.T
) for more than 30 minutes of cumula-
tive time without an increase in circuit capacity. During this oil
recovery mode, the compressor will load fully for 30 seconds.
The unit capacity may exceed system requirements. For more
information, contact your Carrier representative.
L.OUT
(OAT Below Lockout Temp) — When this mode is
active (
Operating Modes
o
MODE
o
L.OUT=
YES
) the unit is
ON and the ambient temperature is below the field pro-
grammed OAT Lockout Temperature. See Low Ambient
Lockout on page 128 for additional details.
MD05
(Ramp Load Limited) — When this mode is active
(
Operating Modes
o
MODE
o
MD05=
YES
) the unit capacity
is limited. See Ramp Loading on page 128 for details.
MD06
(Timed Override in Effect) — When this mode is
active (
Operating Modes
o
MODE
o
MD06=
YES
) the unit is
operating under normal capacity control during a scheduled
unoccupied time. See Timed Override on page 63 for addi-
tional information.
MD09
(Slow Change Override) — When this mode is active
(
Operating Modes
o
MODE
o
MD09=
YES
) the supply air
temperature is close to and is moving toward the Control Point
(
Run Status
o
VIEW
o
CTPT
). While this mode is active, the
control is prohibited from making capacity stage changes.
MD10
(Minimum Off Time Active) — When this mode is
active (
Operating Modes
o
MODE
o
MD10=
YES
) the unit
is prohibited from starting by Minutes Off Time
(
Configuration
o
OPT2
o
DELY
). See Minutes Off Time on
page 128 for additional information.
MD14
(Temperature Reset) — When this mode is active
(
Operating Modes
o
MODE
o
MD14=
YES
) Temperature
Reset is in effect. In this mode, unit is using Temperature Reset
to adjust Active Set Point (
Run Status
o
VIEW
o
SETP
) and
is currently controlling to the modified set point, (
Run Sta-
tus
o
VIEW
o
CTPT
). The set point can be modified based on
outdoor air temperature, space temperature, or a 4 to 20 mA
signal. See Temperature Reset on page 129 for additional
information.
MD15
(Demand Limited) — When this mode is active
(
Operating Modes
o
MODE
o
MD15=
YES
) Demand Limit is
in effect. This indicates that the capacity of the unit is being
limited by the demand limit control option. Because of this
limitation, the unit may not be able to produce the desired sup-
ply air temperature. Demand limit can be controlled by switch
inputs or a 4 to 20 mA signal. See Demand Limit on page 115
for additional information.
MD17
(Low Temperature Cooling) — When this mode is
active (
Operating Modes
o
MODE
o
MD17=
YES
) unit is ON
and the rate of change of the supply air temperature is negative
and decreasing faster than –0.5° F (0.5° C) per minute. Error
between Supply Air Temperature (
Run Status
o
VIEW
o
SAT
)
and Control Point (
Run Status
o
VIEW
o
CTPT
) exceeds
fixed amount. Control will automatically unload the unit if
necessary.
MD18
(High Temperature Cooling) — When this mode is
active (
Operating Modes
o
MODE
o
MD18=
YES
) unit is ON
and the rate of change of the supply air temperature is positive
and increasing. Error between Supply Air Temperature (
Run
Status
o
VIEW
o
SAT
) and Control Point (
Run Sta-
tus
o
VIEW
o
CTPT
) exceeds fixed amount. Control will
automatically load the unit if necessary to better match the
increasing load.
MD21
(High SCT Circuit A),
MD22
(High SCT Circuit B)
— When these modes are active (
Operating Modes
o
MODE
o
MD21=
YES
and/or
MD22=
YES
) unit is ON and
the saturated condensing temperature (SCT) of the circuit is
greater than the calculated maximum limit. No additional
stages of capacity will be added. Unit capacity may be reduced
if SCT continues to rise to avoid high-pressure switch trips by
reducing condensing temperature. If this condition is encoun-
tered, check items listed for alerts T122 – Circuit A High Pres-
sure Trip and T123 – Circuit B High Pressure Trip on
page 170.
MD23
(Minimum Comp On Time) — When this mode is
active (
Operating Modes
o
MODE
o
MD23=
YES
) the unit is
ON, a compressor has just started, and the Minimum Com-
pressor On Time timer of 60 seconds is active. Although the
cooling load may be satisfied, control continues to operate
compressor to ensure proper oil return. This may be an indica-
tion of oversized application or low airflow.
MD25
(Low Sound Mode) — This mode is not supported.
MDTG
(Time Guard Active) — When this mode is active
(
Operating Modes
o
MODE
o
MDTG=
YES
) at least one
compressor is affected by a Time Guard timer. Any time a
compressor is started, it must remain on for 120 seconds. If a
compressor is shut off, it must remain off for 180 seconds.
Unit capacity or compressor staging sequence may be affected
if this mode is active. This is part of the compressor protection
algorithm to prevent rapid cycling of a compressor.
