User Guide

Operation
Condensing unit installation, operation, and
maintenance determine the overall capability of
maintaining a satisfactory pressure by means of fan
speed control. Within the operating range, the P66
control provides air delivery in direct proportion to heat
rejection requirements. This allows the refrigeration
system to perform efficiently in very low ambient
temperatures.
The P66 pressure transducer provides direct response
to changes in condenser pressure, regardless of the
variations in fan delivery curves. The dual input
models select the pressure input from the transducer
sensing the highest pressure.
See Figure 6 for a typical operational sequence for a
P66 control.
97%
90%
10% to 40%
of Line
(model specific)
No fan operation
in this
pressure range.
0
psig
Operating Range
(190/250 psig)
Operating Range
Plus 20 or 30 psi*
*20 psi for 30 psi Effective Throttling Range (ETR)
30 psi for 60 psi Effective Throttling Range (ETR)
350 psig
Motor Voltage
Pressure Input
P66_OP_CHART
Figure 6: Operation Chart for the P66 Fan Speed Control
Table 1: P66 Control Operation
Pressure Input Motor Voltage (VAC, true RMS)
Pressure is between 0 psig and the low end of the
operating range.
0 to 5 volts
Pressure is at the low end of the operating range.
Start voltage (10% to 40% of line - model specific)
Pressure is in the operating range.
Motor voltage varies directly with system pressure from start
voltage to 90% of line voltage.
Pressure is above the operating range.
A further pressure increase of 20 to 30 psi will increase
motor voltage to 97% of the applied voltage.
P66 Series Electronic Fan Speed Controls Installation Instructions 5