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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

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