55
Two-Switch Demand Limiting
(
DM.L.S
= 1
)
This type of demand limiting utilizes 2 discrete inputs:
• Demand Limit Switch 1 Setpoint (
D.L.S1
) — Dmd Limit
Switch Setpoint 1 (0 to 100% total capacity)
• Demand Limit 2 Setpoint (
D.L.S2
) — Dmd Limit Switch
Setpoint 2 (0 to 100% total capacity)
The state of the discrete switch inputs can be found at the local
display:
Inputs
GEN.I
DL.S1
Inputs
GEN.I
DL.S2
The following table illustrates the demand limiting (
Run Sta
-
tus
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
In
-
puts
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 corresponding to a 20
mA input (0 to 100%).
The value of percentage reset is determined by a linear interpo
-
lation 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 Load
-
shed 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 number. This allows the loadshed
function to be disabled until configured.
Upon reception of a redline command, the machine will be pre
-
vented from starting if it is not running. If it is running, then
DEM.L
is set equal to the current running cooling capacity (
Run
Status
COOL
C.CAP
)
.
Upon reception of a loadshed command, the
DEM.L
variable 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 for the 48/50N Series is managed di
-
rectly by the
Comfort
Link controls. The controls are able to cy
-
cle up to 9 stages of outdoor fans to maintain acceptable head
pressure. Fan stages will be turned on or off in reaction to dis
-
charge pressure sensors with the pressure converted to the cor
-
responding saturated condensing temperature.
An option to allow fan speed control (Motormaster
®
) on the
first stage is configured by setting
Configuration
COOL
M.M
= Yes.
There are 5 configurations provided for head pressure control
that can be found at the local display:
Configuration
COOL
M.M
(Motormaster enable)
Configuration
M.PID
SCT.H
(
Maximum Condensing Temp)
Configuration
M.PID
SCT.L
(
Minimum Condensing Temp)
There are up to 5 outputs provided to control head pressure:
Outputs
FANS
CDF.1
— Condenser Fan Output 1
Outputs
FANS
CDF.2
— Condenser Fan Output 2
Outputs
FANS
CDF.3
— Condenser Fan Output 3
Outputs
FANS
CDF.4
— Condenser Fan Output 4
Outputs
FANS
CDF.5
— Condenser Fan Output 5
The specific staging sequence for a unit depends on 3 factors:
the unit size (tonnage), which refrigeration circuits are current
-
ly operating, and whether or not Motormaster control is en
-
abled. See Fig. 6-8 for fan staging sequencing.
The condenser fan output controls outdoor fan contactors and
outdoor fans for each unit tonnage as shown in Fig. 6. Each
stage of fans is also shown. The
Comfort
Link controller adds
or subtracts stages of fans based on
SCT.H
and
SCT.L
. When
the SCT rises above
SCT.H
, a fan stage will be added. The
Comfort
Link controller will continue to add a fan stage every
10 seconds thereafter if the SCT remains above
SCT.H
. If SCT
rises above 130°F, the controller will turn on the maximum fan
stages for the unit. When the SCT drops below the
SCT.L
, a
fan stage will be subtracted. The
Comfort
Link controller will
continue to drop a fan stage every 2 minutes thereafter if the
SCT remains below
SCT.L
.
When a condenser fan output is common to both refrigeration
circuits, in other words, when the fan(s) will affect both Circuit
A and Circuit B, the following logic is used: in order to add a
fan stage, the SCT of either circuit must be above
SCT.H
for
30 seconds and in order to subtract a stage, the SCT of both cir
-
cuits must be below
SCT.L
for 30 seconds.
Whenever the outdoor ambient temperature (OAT) is above
70°F, the maximum stage will always be on when the compres
-
sors are on.
On the initial start-up of a circuit, the condenser fans will start
5 seconds prior to the compressor starting in order to ensure
proper head pressure of the compressor immediately at start-
up. After the compressor starts, the normal head pressure rou
-
tine will begin 30 seconds after the condenser fan pre-start.
What stage fans starts depends on the outdoor ambient tem
-
perature. The 3 situations are:
OAT < 50°F
50 F < OAT < 70°F
OAT > 70°F
See Fig. 6-8 for what stage of fans starts for each scenario.
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
= 4 mA
DML.M
= 12 mA
DML.M
= 20 mA
DEM.L
= 100%
DEM.L
= 90%
DEM.L
= 80%
Содержание WeatherExpert 48N2
Страница 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Страница 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Страница 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Страница 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Страница 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Страница 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Страница 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Страница 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Страница 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Страница 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Страница 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Страница 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Страница 168: ...168 Fig 47 Sensor and Ignition Position Fig 48 Combustion Blower Details SENSOR DETAILS IGNITION DETAILS ...
Страница 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...