Johnson Controls System 350 P352AB Series User manual

System 350 Product Guide 930

Basic Controls Section

Product/Technical Bulletin P352AB

Issue Date 0200

Part No. 24-7664-1903, Rev. — www.johnsoncontrols.com

Code No. LIT-930038

System 350





P352AB Electronic Pressure Control Series

The P352AB controls are On/Off electronic pressure

controls with Single-Pole, Double-Throw (SPDT) relay

output and Light-Emitting Diode (LED) indication. The

P352AB controls are designed with Reverse or Direct

Acting mode of operation, adjustable differential, and

an interchangeable pressure transducer. The P352AB

control will accept S352A Stage Modules to control

stages of Heating, Ventilating, and Air Conditioning

(HVAC) and/or refrigeration equipment.

Three models cover the ranges of 0-100 psi,

90-250 psi, and 240-600 psi, covering most common

refrigeration and air conditioning applications.

As are all System 350™ products, the P352AB control

is housed in a NEMA 1 high-impact thermoplastic

enclosure. The modular design provides easy,

snap-together connections for quick installation and

future expandability.

Figure 1: P352AB Electronic Pressure Control

Features and Benefits

❑Modular Design Provides the flexibility to add S352A Stage

Modules, D352 Display Module, and Y350R

Power Module

❑Plug-together Connectors

and 35 mm DIN Rail

Mounting

Eliminates wiring between modules and

reduces installation costs

❑Three Models Available

with Adjustable Setpoint

Ranges of 0-100 psi,

90-250 psi, and 240-600 psi

Handles pressures required for most fan

cycling and compressor unloading

applications

❑Models Available with

Adjustable Differential from

2-50 psi and 10-100 psi

Enables user to match the equipment cycle

rate and/or sequencing for a given application

❑Field-selectable Direct or

Reverse Acting Mode

Energizes relay output on either an increase

or a decrease in pressure

❑Interchangeable Pressure

Transducer

Increases versatility and serviceability

2 Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin

Application

The P352AB Electronic Pressure Control can be used

as a standalone device or in conjunction with

System 350 plug-together accessory modules for

single or multiple stage refrigeration and HVAC

pressure control applications. Typical applications

include:

●condenser fan cycling

●compressor cycling and unloading

IMPORTANT: The System 350 controls are

intended to control equipment under

normal operating conditions. Where

failure or malfunction of the

System 350 controls 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 systems) intended to

warn of, or protect against, failure or

malfunction of the System 350

controls must be incorporated into

and maintained as part of the control

system.

A typical System 350 pressure control setup includes

the following:

●P352AB Electronic Pressure Control

●S352A Stage Modules

●D352 Digital Display Module

●Y350R Power Module (or 24 VAC transformer)

●P399 Electronic Pressure Transducer

Operation

The P352AB Electronic Pressure Control operates on

24 VAC and has an SPDT relay output. A front panel

LED lights to indicate when the relay is energized.

The P352AB controls are used with the P399

Electronic Pressure Transducers, which are available

in several pressure ranges, and provide a ratiometric

analog signal (0.5 to 4.5 VDC), based on the sensed

pressure.

IMPORTANT: The P352AB controls use an input

signal from the P399 Electronic

Pressure Transducer to determine

pressure in psi (pounds per square

inch). The P399 transducer uses a

sealed-reference of one atmosphere

to determine 0 psi. For more

information on interpreting control

pressure readings, refer to the

P399 Electronic Pressure Transducer

Product/Technical Bulletin,

LIT-125515.

Setpoint

Setpoint is defined as the pressure at which the relay

de-energizes. The setpoint is adjustable between

0 to 100, 90 to 250, and 240 to 600 psi, depending on

the model ordered. (See Table 1.)

Table 1: Setpoint Adjustment Range

P352AB Model No. Setpoint Range

P352AB-2 0 to 100 psi

P352AB-3 90 to 250 psi

P352AB-4 240 to 600 psi

Differential

Differential is defined as the difference in pressure

between energization and de-energization of the

output relay. The differential is adjustable between

2 to 50 and 10 to 100 psi, depending on the control

model. (See Table 2.)

Table 2: Differential Adjustment Range

P352AB Model No. Differential Range

P352AB-2 2 to 50 psi

P352AB-3 10 to 100 psi

P352AB-4 10 to 100 psi

Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin 3

Direct/Reverse Acting Mode

The P352AB controls utilize jumpers (at Jumper

Terminal J1) to select the operation mode. (See

Adjustments (P352AB Control) section and Figure 3.)

When in Direct Acting (DA) mode, the relay

de-energizes when the pressure drops below the

setpoint. When the pressure rises above the setpoint

plus the differential, the relay energizes and the “ON”

LED illuminates.

When in Reverse Acting (RA) mode, the relay

de-energizes when the sensed pressure rises above

the setpoint. When the pressure drops below the

setpoint minus the differential, the relay energizes and

the “ON” LED illuminates.

Note: The P352AB controls are configured for DA

mode at the factory.

Refer to Figure 5 for an example of a typical Direct

Acting/Reverse Acting application.

Dimensions

1-3/16

2-3/8

(61)

7/16

(11)

1-1/2

(40)

1/8 (4)

DIN Rail

Mount

7/8 (22) Conduit

Hole

Mounting Slots

For No. 6 Screws

5 (127)

2-15/16 (75)

2-3/8 (61)

7/8 (22)

2-1/4 (57)

(2.0 m)

13 ft

(4.0 m)

Wiring Harness

6-1/2 ft

P399 Transducer

CONTROLS

JOHNSON

P352

Figure 2: P352AB Control Dimensions, in. (mm)

Mounting

The P352AB Electronic Pressure Control is housed in

a compact NEMA 1 plastic enclosure designed for

standard 35 mm DIN-rail mounting. Four key-slot

mounting holes on the back of the control case are

provided for surface mounting. (See Figure 2.)

Note: When mounting the P352AB control (or any

System 350 Module) to rigid conduit, attach

the hub to the conduit before securing the hub

to the control enclosure.

4 Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin

Adjustments (P352AB Control)

Perform the following steps to adjust the P352AB

control settings. (See Figure 3.) Refer to Figure 5 for

an example of the P352AB control in a typical Direct

Acting/Reverse Acting application.

WARNING: Risk of Electrical Shock.

Disconnect power supply to

avoid possible electrical shock or

equipment damage. More than

one disconnect may be required

to completely de-energize

equipment.

1. Ensure all power to system is off.

2. Remove the P352AB control cover by loosening

the four captive cover screws.

3. Set the mode of operation by positioning the

jumpers (at Jumper Terminal J1) horizontally for

Direct Acting or vertically for Reverse Acting.

Note: The P352AB controls are configured in the

DA mode at the factory.

4. Adjust the differential using the potentiometer

marked DIFF ADJUST to the desired setting.

Clockwise rotation increases the differential.

5. Adjust the setpoint using the setpoint adjustment

dial to the desired setting.

After power is applied to the control, a more

accurate setting of the setpoint can be made by

utilizing the D352A Pressure Display Module.

6. Replace the cover on the control and fasten in

place with screws.

7. Restore power to system.

Module

Connector

Concealed Setpoint

Adjustment Dial

Differential

Potentiometer

N.C.

Relay

N.O.

Terminals

COM

Output

Relay Energized

LED Indicator

Jumper

Position at J1

Reverse Acting

Direct Acting

Cover Screw

(One of Four)

24V

COM

VDC

SEN

Wire

Terminal

Block

Relay

Figure 3: Interior View and Typical Wiring of the P352AB Control

Add-On Modules

The Y350R Power Module, D352 Digital Pressure

Display, and S352A Stage Modules snap together and

plug into the P352AB Electronic Pressure Control via

connectors on both sides of each add-on module.

Y350R Power Module

The Y350R Power Module provides a convenient

method of powering System 350 modules from a

120 or 240 VAC power source.

The Y350R Power Module can be plugged into the

right side of the P352AB controls or any of the add-on

modules. The Y350R Power Module is capable of

providing power to a P352AB control, a D352 Display

Module, and up to five S352A Stage Modules. (Refer

to the System 350TM Y350R Power Module

Product/Technical Bulletin, LIT-930090, for more

information.)

Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin 5

D352 Digital Pressure Display Module

The D352 Display Module receives power, sensor, and

setpoint information from the P352AB control. A

three digit Liquid Crystal Display (LCD) gives a

continuous readout of the sensed pressure. Pushing

the PRESS FOR SETPOINT button displays the

setpoint of the adjoining P352AB control. The button

must be pressed for approximately three seconds.

(Refer to the System 350TM Display Modules

Product/Technical Bulletin, LIT-930070, for more

information.)

S352A Pressure Stage Modules

The S352A Stage Modules receive power, setpoint,

and sensor input from the P352AB controls. As many

as five S352A Stage Modules can plug into the

P352AB controls when powered by the Y350R Power

Module. When powered by an external transformer,

the P352AB controls can use up to nine S352A Stage

Modules. (Refer to the System 350TM S350A

Temperature, S351A Humidity, and S352A Pressure

Stage Modules Product/Technical Bulletin,

LIT-930080, for more information.)

Note: When using an external transformer, the

Y65 Series or other 40 VA Class 2

transformers are recommended.

CAUTION: Verify that the jumpers are in the

proper position before powering

System 350 components. If the

jumpers on the P352AB control

or the S352A Stage Module are

in the wrong position, the device

will activate the relay in response

to the opposite signal. The

DA/RA relay will remain

energized until the error is

corrected.

Adjustments (S352A Stage Module)

Perform the following steps to adjust the S352A stage

module settings. (See Figure 4.) Refer to Figure 5 for

an illustration of the S352A Stage Modules in a typical

Direct Acting/Reverse Acting application.

WARNING: Risk of Electrical Shock.

Disconnect power supply to

avoid possible electrical shock or

equipment damage. More than

one disconnect may be required

to completely de-energize

equipment.

1. Ensure all power to system is off.

Each stage module may be receiving separate

power sources. Make sure all power sources to

each stage module are off.

2. Remove the stage module cover by loosening the

four captive cover screws.

3. Set the mode of operation by positioning the

jumpers (at Jumper Terminal J2) horizontally for

Direct Acting or vertically for Reverse Acting.

4. Adjust the differential using the potentiometer

marked DIFF to the desired setting.

5. Adjust the offset using the potentiometer marked

OFFSET to the desired pressure from the P352AB

control setpoint at which the stage relay will

de-energize (above setpoint with Direct Acting

mode selected or below setpoint with Reverse

Acting mode selected).

6. Replace the S352A stage module cover and

tighten the captive cover screws.

7. Restore power to system.

Module

Connector

Relay Energized

LED Indicator

Offset

Potentiometer

Differential

Potentiometer

Module

Connector

Jumper

Position at J2

Reverse Acting

Direct Acting

N.C.

Relay

N.O.

Terminals

COM

Output

Cover Screw

(One of Four)

Relay

Figure 4: Interior View and Typical Wiring

of the S352A Stage Module

6 Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin

Setpoint

Pressure

Higher

Pressure

S352A

Stage

S352A

Stage

P352AB

Stage

Direct Reverse

OFF

ON = Energized

OFF = De-energized

Differential

Lower

Pressure

OFFSET

Figure 5: Typical Direct Acting/Reverse Acting Application

Using One P352AB Control and Three S352A Stage Modules

Wiring

Refer to the following guidelines and wiring diagrams

for proper wiring and terminal designations.

(See Table 3 and Figures 6 and 7.)

WARNING: Risk of Electrical Shock.

Disconnect power supply before

making electrical connections to

avoid possible electrical shock or

equipment damage. More than

one disconnect may be required

to completely de-energize

equipment.

IMPORTANT: Make all wiring connections in

accordance with the National

Electrical Code and all local

regulations. Use copper

conductors only. Do not exceed

the control’s electrical ratings.

Transducer Wiring

The P352AB control supplies 5 VDC power to the

P399 Electronic Pressure Transducer. The transducer

is wired to three of the four connectors at the terminal

block, located at the upper left of the circuit board.

(See Figures 6 and 7.)

The transducer wiring harness has a shielded cable.

Any additional length of cable should also be shielded

cable. Connect the cable shield to the COM terminal

on the P352AB control. Do not connect the other end

of the cable shield.

Table 3: Connecting the Transducer

to the P352AB Control

P352AB Control

Terminal

Designations

P399 Electronic

Pressure Transducer

Wire Colors

COM Black (Common and Shield)

SEN White (Output Signal)

VDC Red (5 VDC Supply)

Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin 7

P352AB D352AS352A

VAC

Wiring Harness P399 Transducer

LoadLoad

N.O.

Terminals

COM

Output

N.C.

Relay

Wire

Terminal

Block

24V

COM

VDC

SEN

White-SEN

Black-COM

Red-VDC

Shield (Connect

only to COM on P352AB)

Isolate and tape. Do not ground

this end of cable shield.

120 VAC

Figure 6: System 350 Powered by an External Transformer Using 120 VAC Power Supply

120 VAC

P352AB Y350R S352A S352A D352A

S352A

Load Load Load Load

Isolate and tape. Do not ground

this end of cable shield.

P399 Transducer

Wiring Harness

White-SEN

Red-VDC

Black-COM

Wire

Terminal

Block

24V

COM

VDC

SEN

N.O.

Terminals

COM

Output

N.C.

Relay

Shield (Connect

only to COM on P352AB)

Figure 7: System 350 Powered by a Y350R Power Module Using 120 VAC Power Supply

8 Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin

Checkout Procedure

Before applying power, make sure installation and

wiring connections are according to job specifications.

After necessary adjustments and electrical

connections have been made, put the system in

operation and observe at least three complete

operating cycles before leaving the installation.

Troubleshooting

If the System 350 control modules do not appear to

function properly, verify that the proper mode (DA or

RA) has been selected on each control module. Then

perform the following procedures to determine the

problem.

IMPORTANT: The control and the controlled

equipment must be powered and

operating at a stable pressure to

perform many of the following

procedures.

Equipment Needed:

•A reliable pressure gauge connected near the

transducer.

•A reliable and accurate Digital Voltmeter (DVM)

capable of measuring AC voltage and DC voltages

down to ± 0.1 VDC in the 0 to 10 VDC range.

WARNING: Risk of Electrical Shock.

To perform the following

procedures it is necessary to

power the control and the

controlled equipment while the

control cover is removed. Do not

touch any exposed metal

components with anything other

than properly insulated tools or

insulated probes of the digital

voltage meter. Failure to use

properly insulated tools and

probes can result in severe

electrical shock if live line voltage

parts are contacted.

1. Check for proper supply voltage to the Control.

a. Before powering control and equipment, check

that all of the wiring is correct and all of the

connections are tight.

b. Apply power to the control.

c. With the DVM, check the voltage between the

24V and the COM terminals on the terminal

block on the upper left side of the control.

If an external 24 VAC transformer powers

the control, select AC volts on the DVM. The

voltage must be between 20 and 30 VAC.

If a Y350R Power Module powers the

control, select DC volts on the DVM. The

voltage must be between 16 and 38 VDC.

d. If the DVM reading is within the indicated

voltage range, proceed to Step 2.

e. If the DVM reading is not within the indicated

voltage ranges, replace the external

transformer or the Y350R Power Module, and

recheck for proper supply voltage.

2. Check for proper supply voltage to the

pressure transducer.

a. Select DC volts on the DVM and measure the

voltage (VDCS) between VDC and the COM

terminals on the terminal block on the upper

left side of the control.

The voltage must be 5.0 VDC (± 0.1 VDC).

If the voltage is in this range proceed to

Step 3.

b. If the voltage is out of this range, power down

the controlled equipment and disconnect it

from the control. Disconnect the transducer

from the control. With the control powered,

measure the voltage (VDCS) between VDC

and the COM terminals on the terminal block

on the upper left side of the control.

The voltage must be 5.0 VDC (± 0.1 VDC).

If the voltage is in this range, replace the

transducer. If the voltage is out of range,

replace the control.

3. Check pressure transducer for proper output

signal voltage.

a. Measure and record the voltage (Vo) between

the SEN and the COM terminals on the control

terminal block.

b. At the same time, observe and record the

pressure reading (psiT) on the gauge.

Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin 9

c. The transducer output signal voltage (Vo)

increases proportionally to an increase in the

pressure at the transducer (psiT). Use the

graph in Figure 8 to compare the measured

signal voltage to the measured pressure or

use the formula below to compare the voltage

and pressure values.

psi =

( )

VDC

max

1.25 x

VDC

psiT= Pressure measured at transducer

Vo= Transducer output signal voltage (VDC)

VDCS=Supply voltage to the transducer

(measured in step 2a).

Pmax = Transducer pressure range maximum

Example:

The measured pressure at the gauge is

approximately 245 psi (psiT), the measured

transducer output voltage is 2.5 VDC (Vo), the

measured supply voltage to the transducer is

5.03 VDC (VDCS), and the transducer’s rated

range is 0 to 500 psi (Pmax). Use the formula

above to calculate the pressure you would

expect from the measured voltage.

2.5 -

(

5.03 x

)

1.25 x 500

5.03 = 248.1 psi

Since the measured pressure of 245 psi (psiT)

is close to the pressure calculated from the

measured voltage of 248.1 psi, the transducer

output voltage is considered within the desired

range.

Note: Depending on the accuracy of the

instrumentation used to measure the

actual pressure at the transducer

(psiT) and the transducer output

voltage (Vo), the actual and calculated

pressure may not exactly agree.

(10%)

(90%)

(50%)

Output Voltage

(% of Power Supply)

4.5 VDC

2.5 VDC

0.5 VDC

500 psi

P352AB-3

P399B

Pressure (psi)

P352AB Model

P399 Transducer

100 psi

P352AB-2

P399A

P352AB-2

P352AB-3

P352AB-4

Figure 8: Pressure vs. Output Voltage

4. Check the control for proper operation.

Perform Steps 1-3 first.

Note: When the LED is lit, the N.O. contacts are

closed.

a. Determine and record if the control is

in the DA or RA mode of operation.

b. Determine the differential setting.

c. Observe and record the system

pressure at the gauge.

d. If the control is in the DA mode, adjust the

setpoint setting to a value lower than the

observed gauge pressure. If the LED is not lit,

turn the setpoint adjustment knob

counterclockwise until the LED lights

e. With the LED lit, slowly turn the setpoint

adjustment knob clockwise (to increase the

setpoint setting) until the LED goes off.

Observe the gauge pressure, which should be

the same as the setpoint setting when the LED

goes off.

f. Next turn the setpoint adjustment slowly

counterclockwise until the LED lights again.

Observe the gauge pressure, which should be

equal to the differential setting plus the

setpoint setting when the LED lit.

10 Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin

g. If the control is in the RA mode, adjust the

setpoint setting to a value higher than the

observed gauge pressure. If the LED is not lit,

turn the setpoint adjustment knob clockwise

until the LED lights.

h. With the LED lit, slowly turn the setpoint

adjustment knob counterclockwise (to

decrease the setpoint setting) until the LED

goes off. Observe the gauge pressure, which

should be the same as the setpoint setting

when the LED went off.

i. Next turn the setpoint adjustment slowly

clockwise until the LED lights again. Observe

the gauge pressure, which should be equal to

the setpoint setting minus the differential

setting.

5. Check the stage modules for proper operation.

Perform Steps 1-4 first.

If stage modules are not used, proceed to Step 6.

a. Determine and record if the stage module

is in the DA or RA mode of operation.

b. Determine the differential setting.

c. Observe and record the offset setting.

d. Observe and record the system

pressure at the gauge.

e. Use the procedure outlined in Steps 4a-4i to

determine if the stage module is operating

properly. Use Table 4 to determine what the

On and Off setpoint pressure values are for

each module.

f. If a stage module LED and relay do not

perform as expected, adjust the differential

and offset potentiometers to their minimum

value and repeat the previous checks.

g. If a stage module still does not perform

properly, replace the stage module.

6. Check the display module for proper

operation.

If there is no display module in the system, skip

this step.

Perform Steps 1-5 first.

a. Check the gauge pressure (psi) at the

transducer.

b. If the display module does not display the

(approximate) pressure measured at the

gauge, replace the display module.

c. Pressing the button on the display module

should display the current setpoint setting.

If the displayed setpoint is out of the control’s

setpoint pressure range (check scale-plate at the

setpoint knob for control’s pressure range),

replace the control.

Table 4: S352A Stage Module Relay Troubleshooting

Operating Mode LED N.O. Contact

Position

Setpoint Setting Equals

Approximately…

Direct Acting (DA) On Closed (psi reading) -offset -differential

Direct Acting (DA) Off Open (psi reading) -offset

Reverse Acting (RA) On Closed (psi reading) +offset +differential

Reverse Acting (RA) Off Open (psi reading) +offset

Repairs and Replacement

Field repairs or calibration must not be made.

Replacement controls and pressure transducers are

available through your local Johnson Controls

representative.

This manual suits for next models

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