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Demand Limit Control
The term demand limit control refers to the restriction of the
machine’s mechanical cooling capacity to control the amount
of power that a machine may use.
Demand limiting is possible via two means:
Two discrete inputs tied to demand limit set point percentages.
OR
A 4 to 20 mA input that can reduce or limit capacity linearly to
a set point percentage.
In either case, it will be necessary to install a CEM. The control
interfaces to a switch input at TB202-10 and TB202-11.
DEMAND LIMIT DISCRETE INPUTS
First, set DM.L.S in Configuration
DMD.L to 1 (2 switches).
When Inputs
GEN.I
DL.S1 (Demand Switch no. 1) is OFF,
the control will not set any limit to the capacity, and when ON,
the control sets a capacity limit to the Configuration
DMD.L
D.L.S1 set point.
Likewise, when Inputs
GEN.I
DL.S2 (Demand Switch no. 2)
is OFF, the control will not set any limit to the capacity, and when
ON, the control sets a capacity limit to the Configuration
DMD.L
D.L.S2 set point.
If both switches are ON, Inputs
GEN.I
DL.S2 is used as the
limiter of capacity.
Under Configuration
SW.LG, set the logic state appropriate-
ly for the action desired. Set the DL1.L and DL2.L configura-
tions. They can be set normally open or normally closed. For
example, if DL1.L is set to OPEN, the user will need to close
the switch to cause the control to limit capacity to the demand
limit 1 set point. Likewise, if DL1.L is set to CLSE (closed),
the user will need to open the switch to cause the control to
limit capacity to the demand limit 1 set point.
DEMAND LIMIT 4 TO 20 mA INPUT
Under Configuration
DMD.L, set configuration DM.L.S to 2
(2 = 4 to 20 mA control). Under the same menu, set D.L.20 to a
value from 0 to 100 to set the demand limit range. For exam-
ple, with D.L.20 set to 50, a 4 mA signal will result in no limit
to the capacity and 20 mA signal will result in a 50% reduction
in capacity.
Economizer/Outdoor Air Damper Control
There are multiple methods for externally controlling the econ-
omizer damper.
IAQ DISCRETE INPUT CONFIGURATION
The IAQ (indoor air quality) discrete input configuration requires
a CEM module (optional) to be installed and an interface to a
switch input at TB202-12 and TB202-13. The state of the input on
the display can be found at Inputs
AIR.Q
IAQ.I.
Before configuring the switch functionality, first determine
how the switch will be read. A closed switch can indicate ei-
ther a low IAQ condition or a high IAQ condition. This is set at
Configuration
SW.LG
IAQ.L. The user can set what a low
reading would mean based on the type of switch being used.
Setting IAQ.L to OPEN means that when the switch is open
the input will read LOW. When the switch is closed, the input
will read HIGH. Setting IAQ.L to CLSE (closed) means that
when the switch is closed the input will read LOW, and there-
fore, when the switch is open the switch will read HIGH.
There are two possible configurations for the IAQ discrete input.
Select item Configuration
IAQ
AQ.CF
IQ.I.C and config-
ure for either 1 (IAQ Discrete) or 2 (IAQ Discrete Override).
IQ.I.C = 1 (IAQ Discrete)
If the user sets IQ.I.C to 1 (IAQ Discrete), and the switch logic
(Configuration
SW.LG
IAQ.L) is set to OPEN, then an
open switch reads low and a closed switch reads high.
If the switch is open, the economizer will be commanded to the
IAQ Demand Vent Minimum Position. If the outdoor flow sta-
tion is installed and outdoor air cfm can be read, the economiz-
er will move to the IAQ Demand Vent Minimum Flow CFM
control setting.
These settings may be adjusted and are located here:
Configuration
IAQ
DCV.C
IAQ.M
Configuration
IAQ
DCV.C
O.C.MN
If the switch is closed, the IAQ reading will be high and the
economizer will be commanded to the Economizer Minimum
Position. If the outdoor airflow station is installed and outdoor
air cfm can be read, the economizer will move to the Econo-
mizer Minimum Flow CFM control setting.
These settings may be adjusted and are located here:
Configuration
IAQ
DCV.C
EC.MN
Configuration
IAQ
DCV.C
O.C.MX
IQ.I.C = 2 (IAQ Discrete Override)
If the user sets IQ.I.C to 2 (IAQ Discrete Override), and Con-
figuration
SW.LG
IAQ.L is set to OPEN, then an open
switch reads low and a closed switch reads high.
If the switch reads low, no action will be taken. If the switch reads
high, the economizer will immediately be commanded to the IAQ
Economizer Override Position. This can be set from 0 to 100%
and can be found at Configuration
IAQ
AQ.SP
IQ.O.P.
FAN CONTROL FOR THE IAQ DISCRETE INPUT
Under Configuration
IAQ
AQ.CF, the IQ.I.F (IAQ Dis-
crete Input Fan Configuration) must also be set. There are three
configurations for IQ.I.F. Select the configuration that will be
used for fan operation. This configuration allows the user to
decide whether the IAQ discrete switch will start the fan (if the
supply fan is not already running), and in which state of occu-
pancy the fan will start.
IAQ ANALOG INPUT CONFIGURATION
This input is an analog input located on the main base board
(MBB). There are 4 different functions for this input. The loca-
tion of this configuration is at Configuration
IAQ
AQ.CF
IQ.A.C.
The functions possible for IQ.A.C are:
• 0 = no IAQ analog input
• 1 = IAQ analog input
• 2 = IAQ analog input used to override to a set position
• 3 = 4 to 20 mA 0 to 100% economizer minimum position
control
• 4 = 0 to 10,000 ohms 0 to 100% economizer minimum po-
sition control
Options 2, 3, and 4 are dedicated for third party control.
IQ.A.C = 2 (IAQ Analog Input Used to Override)
Under Configuration
IAQ
AQ.SP, set IQ.O.P (IAQ Econ-
omizer Override Position). The IQ.O.P configuration is adjust-
able from 0 to 100%. These configurations are also used in
conjunction with Configuration
IAQ
AQ.CF
IQ.A.F
(IAQ 4 to 20 mA Fan Configuration). There are three configu-
rations for IQ.A.F and they follow the same logic as for the
discrete input. This configuration allows the user to decide (if
the supply fan is not already running), if the IAQ Analog Mini-
mum Position Override input will start the fan, and in which
state of occupancy the fan will start.
IQ.I.F = 0 Minimum Position Override Switch input will
not start fan
IQ.I.F = 1 Minimum Position Override Switch input will
start fan in occupied mode only
IQ.I.F = 2 Minimum Position Override Switch input will
start fan in both occupied and unoccupied
modes
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