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46
Table 57 — Demand Limit Configuration
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:
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
→
COOL
→
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
.
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
→
COOL
→
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
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
→
COOL
→
C.CAP
).
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
→
COOL
→
M.M.
) must
be set to YES if the unit size (
Configuration
→
UNIT
→
SIZE
)
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
→
SCT.A
and
SCT.B
)
, which are connected
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
→
REF.P
→
DP.A
and
DP.B
.
There are two configurations provided for head pressure
control that can be found at the local display:
•
Configuration
→
COOL
→
M.M.
– Motormaster Control?
•
Configuration
→
COOL
→
HPSP
– Head Pressure Set Point
There are two condenser fan relays used to control head
pressure:
•
Outputs
→
FANS
→
CD.F.A
-
Condenser Fan A
•
Outputs
→
FANS
→
CD.F.B
-
Condenser Fan B
ITEM
EXPANSION
RANGE
UNITS
CCN POINT
DEFAULT
DMD.L
DEMAND LIMIT CONFIG.
DM.L.S
Demand Limit Select
0 - 3
DMD_CTRL
0
D.L.20
Demand Limit at 20 ma
0 - 100
%
DMT20MA
100
SH.NM
Loadshed Group Number
0 - 99
SHED_NUM
0
SH.DL
Loadshed Demand Delta
0 - 60
%
SHED_DEL
0
SH.TM
Maximum Loadshed Time
0 - 120
min
SHED_TIM
60
D.L.S1
Demand Limit Sw.1 Setpt.
0 - 100
%
DLSWSP1
80
D.L.S2
Demand Limit Sw.2 Setpt.
0 - 100
%
DLSWSP2
50
Switch Status
Run Status
→
COOL
→
DEM.L = 1
Inputs
→
GEN.I
→
DL.S1
= OFF
Inputs
→
GEN.I
→
DL.S2
= OFF
100%
Inputs
→
GEN.I
→
DL.S1
= ON
Inputs
→
GEN.I
→
DL.S2
= OFF
Configuration
→
DMD.L
→
D.L.S1
Inputs
→
GEN.I
→
DL.S1
= ON
Inputs
→
GEN.I
→
DL.S2
= ON
Configuration
→
DMD.L
→
D.L.S2
Inputs
→
GEN.I
→
DL.S1
= OFF
Inputs
→
GEN.I
→
DL.S2
= ON
Configuration
→
DMD.L
→
D.L.S2
D.L.20
= 80%
D.L.20
= 80%
D.L.20
= 80%
DML.M
= 4mA
DML.M
= 12 mA
DML.M
= 20mA
DEM.L
= 100%
DEM.L
= 90%
DEM.L
= 80%
Summary of Contents for WEATHERMAKER 48AJ020
Page 95: ...95 Fig 13 Typical Main Control Box Wiring Schematic A48 7787 ...
Page 96: ...96 TO NEXT PAGE Fig 14 Auxiliary Control Box Wiring Schematic A48 7294 ...
Page 98: ...98 Fig 15 Typical 2 Stage Gas Heat Wiring Schematic Size 051 and 060 Units Shown A48 6866 ...
Page 102: ...102 TO NEXT PAGE Fig 18 Typical Power Schematic Size 051 and 060 Units Shown A48 7298 ...
Page 104: ...104 Fig 19 Controls Option Wiring Schematic A48 7810 ...
Page 105: ...105 Fig 20 Small Chassis Component Location Size 020 035 Units A48 7301 ...
Page 106: ...106 Fig 21 Large Chassis Component Locations Size 036 060 Units A48 7302 ...