Application Note P35
Issue Date November 18, 2002
P35 Pressure Transducer and VFD66 Control
Application
IMPORTANT: The P35 Pressure Transducer is
intended to provide an input to equipment under
normal operating conditions. Where failure or
malfunction of a P35 Pressure Transducer could
lead to an abnormal operating condition that could
cause personal injury or damage to the equipment
or other property, other devices (limit or safety
controls), or systems (alarm or supervisory)
intended to warn of, or protect against, failure of
the P35 Pressure Transducer must be
incorporated into and maintained as part of the
control system.
The P35 Pressure Transducer provides a control
signal to the VFD66 Series Condenser Fan Speed
Control. The P35 transducer and VFD66 control
work together to vary the speed of the condenser
fan based on refrigerant pressure and to provide the
optimum head pressure for the given load demand
on the refrigeration or air conditioning system.
Installation
Dimensions
Side View
3-3/4 (97)
2-1/8
(54)
Two Mounting Holes
Along Back Side
2-15/16
(74)
1-1/16
(27)
Top View
Range Adjustment Screw
1 (25)
Turn range adjustment screw
clockwise to raise Setpoint.
Turn range adjustment screw
counterclockwise to lower Setpoint.
Figure 2: Dimensions of the P35 Pressure
Transducer, in. (mm)
Figure 1: P35 Pressure Transducer
© 2002 Johnson Controls, Inc.
Code No. LIT-121418
Part No. 24-7664-1792, Rev. C
1
www.johnsoncontrols.com
Holes for Attaching
to P35 Transducer
A
B
Connect the P35 transducer to the VFD66 control using
three 16-22 gauge wires, each less than 50 ft (15 m) in
length. Insert the wires through the terminal block
housing and connect the wires to the terminal block.
Wiring the P35 Transducer
Terminal
Block
P35
Transducer
1/2 (13)
Terminal
Block Housing
Fastening
Screw
2-3/8 (60)
Holes for Surface Mount
1-5/16 in.
33 mm
Figure 3: Dimensions of the Mounting Bracket,
in. (mm)
Mounting
IMPORTANT: Improper mounting of the P35
transducer can result in malfunction of or damage
to the transducer. Mount the transducer upright
and level. Locate pressure tap points on the top
side of the refrigerant lines. Mount the transducer
where it is not exposed to rain or other moisture.
IMPORTANT: If the P35 pressure transducer is
installed on equipment that contains hazardous or
regulated materials, such as refrigerants or
lubricants, the installer and user should observe all
regulations governing the handling and
containment of those materials.
The P35 transducer has an integral Schrader
depressor and mounts directly to a 1/4 in. SAE male
flare fitting. Mount the P35 transducer downstream
from the coil, away from severe pressure pulsation
and mechanical vibrations, which can occur near the
compressor discharge.
Use the holes in the mounting bracket to attach the
transducer to a flat surface. See Figure 3. Use only
the screws provided to mount the transducer and
mounting bracket.
Wiring
!
WARNING: Risk of Electrical Shock.
Disconnect power supply before making electrical
connections to avoid possible electrical shock.
2
Small
Slot
2
1
Metal Spacer
Threaded
Bushing
3
Front
Rubber Grommet
Insert Wires
Figure 4: Terminal Block Assembly
Use the following instructions when assembling and
wiring the terminal block assembly: (See Figure 4.)
1. Remove the fastening screw.
2. Locate the small slot on the side of the terminal
block and use a small standard screwdriver or
similar tool to carefully remove the terminal block.
3. Remove the threaded bushing and insert the wires
through the bushing, spacer, grommet, and terminal
block housing as shown in Figure 4.
4. Connect the wires to the terminal block. Note the
numbering sequence molded into the front of the
terminal block, shown in Figure 4.
5. Insert the terminal block into the housing, and
secure both to the P35 transducer with the fastening
screw.
6. Tighten the threaded bushing.
Wiring the VFD66 Control
Refer to Table 1 and Figure 5 for proper wiring
configuration for single or dual-transducer applications.
For further information, refer to Wiring in the VFD66
Series Condenser Fan Speed Controls
Product/Technical Bulletin (LIT-125467).
P35 Pressure Transducer and VFD66 Control Application Note
Table 1: Connecting the P35 Transducer to the
VFD66 Control
Input Device
Input Device
Terminal
P35AG-9200R
Transducer
1
1
2
2 (or 3)*
3
4
*
VFD66 Control
TB3 Terminal
P35 Transducer
When used with a VFD66 control, the P35 transducer
setpoint is the pressure required to operate the
condenser fan motor at full speed. Reducing the sensed
pressure at the transducer below setpoint reduces the
fan motor speed.
2
3
IMPORTANT: After adjusting control settings and
before leaving installation, cycle the controlled system
at least three times at normal operating conditions
using reliable pressure gauges to verify proper
transducer operation and settings.
Standard Input mode is the most commonly used mode.
The majority of input devices compatible with the VFD66
controls are used with this mode. The input device
determines the setpoint and proportional band.
Use Terminal 3 for input from a second input
device.
1
Setup and Adjustments
TB3
1 234
The setpoint is factory set at 232 psi (1600 kPa) but may
be adjusted between 203 and 350 psi (1400 to 2314 kPa).
The fixed throttling range is 46 psi (317 kPa). At 46 psi
below setpoint, the fan motor shuts off.
Figure 5: Wiring P35 Transducers to the
VFD66 Control
Turn the range adjustment screw clockwise to raise the
setpoint, and counterclockwise to lower the setpoint.
Refer to Figure 2 for the location of the range adjustment
screw and Figure 6 for graphical representation of
throttling and setpoint ranges.
RPM
Pressure Connections
Connect the refrigerant-side flare connector to the
appropriate high-side pressure tap point.
Follow the guidelines below when making pressure
connections:
•
Use Pressure Tap Points Located on the Top
Side of the Refrigerant Lines.
This reduces the possibility of oil, liquids, or
sediment accumulating at the pressure
connection, which could cause transducer
malfunction.
•
Do Not Overtighten Flare Nuts on Pressure
Connection Line Fittings.
Overtightening flare connections may damage
the threads on the flare nuts or flare connectors
and result in refrigerant leaks. Do not exceed
9 lb⋅ft (12 N⋅m) of torque when tightening brass
flare connections.
•
Setpoint
203 to 350 psig
(1400 to 2413 kPa)
100%
Curve A
P1=40%
P2=CCW
Curve B
P1=30%
P2=CW
50%
40%
Idle
30%
Curve C
P1=0%
P2=CCW or CW
0%
Minimum
Motor Speed
Set by P1
Pressure
Proportional Band
Fixed Throttling Range
46 psig (317 kPa)
Factory
Setpoint
232 psig
(1600 kPa)
Figure 6: Setpoint Range for the P35AG-9200R
Avoid Severe Pressure Pulsation at Pressure
Tap Points.
Install pressure connection lines to pressure tap
points away from the compressor discharge to
minimize the effects of pressure pulsation from
reciprocating compressors.
P35 Pressure Transducer and VFD66 Control Application Note
3
Table 2: Standard Input Mode
J2
Jumper
Position
J3
Jumper
Position
P1:
Minimum
Motor
Speed
Installed
Removed
Can be set
at 0-50% of
maximum
motor
speed.
Repairs and Replacement
P2: Motor
Action at
Minimum
Speed
CCW:
Motor idles.
CW: Motor
shuts off.
Do not attempt to repair or recalibrate the
P35 transducer. A replacement transducer is available
through your local Johnson Controls/PENN™
representative.
Table 3: Replacement Part
Product Code Number
P35AG-9200R
P1 adjusts the minimum speed of the motor. The
minimum speed is adjustable from 0 to 50% of total
motor speed.
P2 determines whether the motor idles at minimum
speed or shuts off at minimum speed. P2 must be
set at full Counterclockwise (CCW) or full Clockwise
(CW) position; intermediate settings have no effect.
Figure 6 illustrates three possible motor speed
curves. When P2 is rotated fully CCW, the motor
idles at the minimum speed set by P1 at input values
below the end of the proportional band (Curve A in
Figure 6). When P2 is rotated fully CW, the motor
shuts off at the minimum speed set by P1 when the
input is below the bottom end of the proportional
band (Curve B in Figure 6).
In Curve C, the minimum motor speed (P1) is set at
0% of maximum motor speed, and the position of
P2 has no effect.
For applications with a single input, install the
supplied jumper on both pins of Terminal J8 on the
VFD66 control. For dual input applications, place
jumper on one pin of Terminal J8. Refer to Adjusting
the Control Settings in the VFD66 Series Condenser
Fan Speed Controls Product/Technical Bulletin
(LIT-125467) for further instructions.
Operation
The VFD66 control supplies a constant 5 VDC
source to the P35 transducer. The transducer
responds to refrigerant pressure changes by varying
a proportional signal (0.5-4.5 VDC) to the
VFD66 control.
As the pressure increases, the P35 transducer
increases the DC voltage signal to the
VFD66 control. The VFD66 control responds by
increasing the condenser fan motor speed
proportionally.
Increased airflow over the condenser reduces the
refrigerant pressure. As the pressure decreases, the
P35 transducer decreases the DC voltage signal to
the VFD66 control, which slows the fan motor.
4
P35 Pressure Transducer and VFD66 Control Application Note
Description
Direct-mount pressure
transducer
Technical Specifications
Product
Setpoint Range
Fixed Throttling Range
Output
Power Requirements
Operating Conditions
Ambient Storage
Conditions
Agency Compliance
P35 Pressure Transducer
203-350 psig (1400-2413 kPa)
46 psi (317 kPa)
0.5 VDC to 4.5 VDC
5 VDC from VFD66 Control
-31-131°F (-35-55°C), 0-95% RH (noncondensing)
-40-158°F (-40-70°C), 0-95% RH (noncondensing)
UL Recognized, File E29374, CCNs NKPZ2 (US), NKPZ8 (Canada)
The performance specifications are nominal and conform to acceptable industry standards. For application at conditions beyond these
specifications, consult Johnson Controls/Penn Application Engineering at (800) 275-5256. Johnson Controls, Inc. shall not be liable for
damages resulting from misapplication or misuse of its products.
Controls Group
507 E. Michigan Street
P.O. Box 423
Milwaukee, WI 53201
Printed in U.S.A.
www.johnsoncontrols.com
P35 Pressure Transducer and VFD66 Control Application Note
5