Trane CVHE Troubleshooting Manual page 95

External Current Limit is an option that allows the customer to change the current limit
setpoint from a remote location. The External Current Limit Setpoint is found on Options
module terminals J7-11 and J7-12.
UCP2 accepts either a 2-10 VDC or 4-20 mA analog input to set the chillers external current
limit setpoint. 2-10 VDC and 4-20mA each correspond to a 40 to 120% RLA range.
The following equations are what UCP2 uses:
As generated from external source
As processed by UCP2
The following graph shows External Current Limit Setpoint with a 2-10 VDC input:
120
110
100
90
80
70
60
50
40
2 2.5 3
CVHE-SB-32A
External Current Limit Setpoint
VDC=.10*(%)-2.0
%=10.0*(VDC)+20.0
3.5 4 4.5 5 5.5
Volts DC
Voltage Signal
6 6.5 7 7.5 8 8.5
Current Signal
mA=.20(%)-4.0
%=5.0(mA)+20.0
% RLA
9 9.5 10
90