Carrier 48AJ Operating And Service Manual page 46

ITEM
DMD.L DEMAND LIMIT CONFIG.
DM.L.S Demand Limit Select
D.L.20 Demand Limit at 20 ma
SH.NM Loadshed Group Number
SH.DL Loadshed Demand Delta
SH.TM Maximum Loadshed Time
D.L.S1 Demand Limit Sw.1 Setpt.
D.L.S2 Demand Limit Sw.2 Setpt.
Two-Switch Demand Limiting (DM.L.S = 1) — This type of
demand limiting utilizes two discrete inputs:
Demand Limit Switch 1 Setpoint (D.L.S1) — Dmd Limit
Switch Setpoint 1 (0-100% total capacity)
Demand Limit 2 Setpoint (D.L.S2) — Dmd Limit Switch
Setpoint 2 (0-100% total capacity)
The state of the discrete switch inputs can be found at the lo-
cal display:
→ →
Inputs GEN.I DL.S1
→ →
Inputs GEN.I DL.S2
The following table illustrates the demand limiting (Run
→ →
Status COOL DEM.L) that will be in effect based on the
logic of the applied switches:
Switch Status
→ →
Inputs GEN.I DL.S1 = OFF
→ →
Inputs GEN.I DL.S2 = OFF
→ →
Inputs GEN.I DL.S1= ON
→ →
Inputs GEN.I DL.S2 = OFF
→ →
Inputs GEN.I DL.S1= ON
→ →
Inputs GEN.I DL.S2 = ON
→ →
Inputs GEN.I DL.S1= OFF
→ →
Inputs GEN.I DL.S2 = ON
4-20 mA Demand Limiting (DM.L.S = 2) — If the unit has
been configured for 4 to 20 mA demand limiting, then the
→ →
Inputs 4-20 DML.M value is used to determine the
amount of demand limiting in effect (Run Status
DEM.L). The Demand Limit at 20 mA (D.L.20) configuration
must be set. This is the configured demand limit correspond-
ing to a 20 mA input (0 to 100%).
The value of percentage reset is determined by a linear
interpolation from 0% to "D.L.20"% based on the Inputs
→
4-20 DML.M input value.
The following examples illustrate the demand limiting
→ →
(Run Status COOL DEM.L) that will be in effect based on
amount of current seen at the 4 to 20 mA input, DML.M.
D.L.20 = 80% D.L.20 = 80%
DML.M = 4mA DML.M = 12 mA
DEM.L = 100% DEM.L = 90%
CCN Loadshed Demand Limiting (DM.L.S = 3) — If the unit
has been configured for CCN Loadshed Demand Limiting,
then the demand limiting variable (Run Status
DEM.L) is controlled via CCN commands.
The relevant configurations for this type of demand limiting
are:
Loadshed Group Number (SH.NM) — CCN Loadshed Group
number
Loadshed Demand Delta (SH.DL) — CCN Loadshed
Demand Delta
Table 57 — Demand Limit Configuration
EXPANSION
→ →
Run Status COOL DEM.L = 1
100%
→ →
Configuration DMD.L D.L.S1
→ →
Configuration DMD.L D.L.S2
→ →
Configuration DMD.L D.L.S2
→ →
COOL
D.L.20 = 80%
DML.M = 20mA
DEM.L = 80%
→
COOL
RANGE UNITS
0 - 3
0 - 100 %
0 - 99
0 - 60 %
0 - 120 min
0 - 100 %
0 - 100 %
Maximum Loadshed Time (SH.TM) — CCN Maximum
Loadshed time
The Loadshed Group Number (SH.NM) corresponds to
the loadshed supervisory device that resides elsewhere on
the CCN network and broadcasts loadshed and redline
commands to its associated equipment parts. The SH.NM
variable will default to zero which is an invalid group num-
ber. This allows the loadshed function to be disabled until
configured.
Upon reception of a redline command, the machine will be
prevented from starting if it is not running. If it is running,
then DEM.L is set equal to the current running cooling capac-
→
ity (Run Status
Upon reception of a loadshed command, the DEM.L vari-
able is set to the current running cooling capacity (Run Status
→ →
COOL C.CAP) minus the configured Loadshed Demand
Delta (SH.DL).
A redline command or loadshed command will stay in
effect until a Cancel redline or Cancel loadshed command is
received, or until the configurable Maximum Loadshed time
(SH.TM) has elapsed.
HEAD PRESSURE CONTROL — Condenser head pressure
control for the 48/50A series rooftops is controlled directly by
the unit, except when the unit is equipped and configured for
Motormaster® V control. See Table 58. If the unit is equipped
with the accessory Motormaster V control, the Motormaster
Installed configuration (Configuration
be set to YES if the unit size (Configuration
is 60 tons. This is because condenser fan relay A must be ener-
gized to enable Motormaster V control. The size 60 unit offers
3 stages of head pressure control and is the one case where con-
denser fan relay A may be requested off during head pressure
→
control operation. By configuring M.M. to YES, the control is
instructed not to turn off the relay to attempt 3 stages of head
pressure control.
The saturated condensing temperature (SCT) sensors (Tem-
→
peratures REF.T
to the condenser coils in circuit A and B, are used to measure
the saturated condensing temperature and may be used to con-
trol head pressure. The equivalent refrigerant pressure values
can be viewed under Pressures
There are two configurations provided for head pressure
control that can be found at the local display:
→
• Configuration
• Configuration
There are two condenser fan relays used to control head
pressure:
→
• Outputs FANS
→
• Outputs FANS
46
CCN POINT
DMD_CTRL 0
DMT20MA 100
SHED_NUM 0
SHED_DEL 0
SHED_TIM 60
DLSWSP1 80
DLSWSP2 50
→
COOL C.CAP).
→
COOL
→
→
SCT.A and SCT.B), which are connected
→ →
REF.P DP.A and DP.B.
→ →
COOL M.M. – Motormaster Control?
→ →
COOL HPSP – Head Pressure Set Point
→
CD.F.A - Condenser Fan A
→
CD.F.B - Condenser Fan B
DEFAULT
→
M.M.) must
→
UNIT SIZE)