Specifications
40
Table 45 — 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)—DmdLimit
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)thatwillbeineffectbasedonthe
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 valueisusedtodeterminethe
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)thatwillbeineffectbasedon
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 46. 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 (Te m-
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 –HeadPressureSetPoint
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
=12mA
DML.M
= 20mA
DEM.L
= 100%
DEM.L
= 90%
DEM.L
=80%