Johnson Controls VFD66 Series Product/Technical Bulletin page 10

Electronic Pressure Transducer Input Mode
IMPORTANT: Minimum motor speed and motor
action at minimum speed cannot be set in this mode.
The VFD66 controls work with most 0-5 VDC or
0-10 VDC electronic pressure transducers. For best
results, use 0-5 VDC, ratiometric P499 Electronic
Pressure Transducers. Ratiometric transducers vary
the signal voltage from 10-90% of the 5 VDC supply
power as the pressure goes from minimum to
maximum of the transducer rating.
Note: Non-ratiometric transducers generate more
error than ratiometric transducers. 0-10 VDC P499
transducers are not ratiometric.
The J7 jumper position sets the input signal voltage
range. Install the J7 jumper when using a 0-5 VDC
transducer. Remove the J7 jumper when using a
0-10 VDC transducer.
Note: Applications using 0-10 VDC transducers
require a separate 15 VDC power supply.
The J3 jumper position establishes the low or high
pressure range of P1 (Table 9).
P1 adjusts the pressure setpoint and establishes the
pressure value at which the VFD66 controls drive the
fan motor at maximum speed.
10 VFD66 Series Condenser Fan Speed Controls Product/Technical Bulletin
P2 adjusts the proportional band over which fan motor
speed is controlled.
Figure 13 illustrates J3, P1, and P2 settings in
Electronic Pressure Transducer Input mode with a
P499 transducer (0-500 psi). If the jumper on J3 is in
the removed position, P1 adjusts the setpoint between
200-350 psi. The fan motor starts when pressure
reaches 200 psi (Setpoint – Proportional Band) and
maximum motor speed (100% RPM) is reached at
250 psi (Setpoint).
RPM
100%
50%
(200 psi)
Figure 13: Electronic Pressure Transducer Input
Mode, 0-500 psi P499 Transducer
(250 psi)
Pressure
Proportional Band
Set by P2
Setpoint
25–100 psi
Set by P1 and J3
(50 psi)