LG PQDSBC1 Owner's Manual

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Dry Contact with Economizer Interface

This manual describes how to install and configure the Dry Contact with Economizer Interface, Model PQDSBC1. The dry contact is used with  

LG Electronics’ Variable Refrigerant Flow (VRF) Systems. The Economizer is an indoor unit (IDU) that allows or prevents outside air entering conditioned 

spaces through the air ducts of the VRF system. To economically help satisfy conditioned zones that call for cooling, the Economizer routes cool outside 

air through the ducted system to these zones. For zones that call for heating, the dry contact control prevents the Economizer from routing outside air to 

those spaces. The dry contact controls Economizer operation according to its internal control settings and external control signals. 

 

Other Dry Contact Functions

In addition to controlling an Economizer, the dry contact can be configured to interface with other types of indoor units such as high and low 

static ducted units and vertical air handlers. Configure the dry contact as necessary for your system.

Component Parts

Figure 1 shows dry contact components. The dry contact is composed of a plastic 

case, an internal printed circuit board (PCB), a communications cable (not shown), 

and mounting hardware (not shown). Table 1 lists and describes the connectors 

and controls on the internal PCB. These components are connected and config-

ured during the installation procedure.

Dry Contact Assembly

Top

Bottom

1

CN_INDOOR

Connector for the included dry contact to indoor unit cable.

2

CN_PI485

PI485 connector. Used only with PI485 PCB (additional component, not included)

3

CHANGE_OVER_SW

Must be set to match voltage applied to input terminals A, B, and common.

4

CN_CONTROL

Terminals for two contact closure input signals: A, B, and common.

5

CONTROL_MODE_SW Rotary switch. Selects dry contact unit function.

6

SETTING_SW

DIP switch. Set as necessary for your system.

7

TEMP_SETTING

Rotary switch. Selects temperature setpoint for the connected indoor unit.

8*

CN_OUT (O1, O2)

Two terminal connections. In mode E (economizer), outputs Cooling Thermal Mode On signal when cooling is 

demanded. In all other modes, if indoor unit is operating, contact closes and outputs an indoor unit ON status signal.

9*

CN_OUT (E3, E4)

Two terminal connections. Not used in operating mode E (economizer). In all other operating modes, if the indoor 

unit has an operational error, contact closes and outputs a signal.

10

DISPLAY_LED

LED that displays the operational and communication status of the dry contact.

11

RESET_SW

Pushbutton reset switch.

Table 1:  PCB Connectors and Controls

Figure 1:  Dry Contact Components

* Outputs function differently depending on configured mode.

Printed Circuit Board

NOT

USED

e

CN_OUT

CHANG

E

OVER_S

W

VOLT

NON
VOLT

TEMP

SETTING

COM A B

O1 O2 E3 E4