Input Values Vs. External Chilled Water Setpoint - Trane RTAA-70 Installation & Maintenance Manual

R series air-cooled rotary liquid chillers

Table of Contents

Installation — Electrical

2. Isolated 2-10 VDC Voltage Source Input.

Set DIP Switch SW1-1 of Options Module 1U2 to "OFF" . Connect the voltage

source to terminals TB1-4 (+) and TB1-5 (-) on Options Module IU2. CWS is

now based on the following equation:

CW Setpoint °F = (VDC x 125) - 16.25

Sample values for CWS vs. VDC signals are shown in

Minimum setpoint = 0 F(2.0 VDC input )

Maximum setpoint = 65 F ( 9.4 VDC input )

Maximum continuous input voltage = 15 VDC

Input impedance (SW1-1 on) = 40.1 Kohms

3. Isolated 4-20 mA Current Source Input.

Set DIP Switch SW1-1 of Options Module 1U2 to "ON" . Connect the current

source to terminals TB1-4 (+) and TB1-5 (-). CWS is now based on the

following equation:

Setpoint °F = (mA x 4.0625) - 16.25

Sample values for CWS vs., mA signals are shown in

Minimum setpoint = 0F(40mA)

Maximum setpoint = 65 F (18.8 mA)

Maximum continuous input voltage = 30 mA

Input impedance (SW1-1 off) = 499 ohms

NOTE: The negative terminal TB1 -5 is referenced to the UCM chassis

ground. To assure correct operation, 2-10 VDC or 4-20 mA signals must be

isolated or "floating" with respect to the UCM chassis ground.

Table 14