Sub-Zero SZ-7552-P User Manual

Amongst others features, an important one is that
Incase one compressor is not capable of handling the
load, the second compressor will activate and both
compressors will cutout at the lowest set point.
SZ-7552 is two compressor controller with separate
setpoints, differentials and time delays for each
compressor.
The controller features cycling of compressors so that
there is no overload on one compressor.
They are specifically designed for air conditioning
applications wherein the compressor cuts off at setpoint
and is restarted at a temperature of setpoint plus
differential.
Instruction for SZ-7552-P
General Description
1
2
INDEX
4
Parameter
Setting
Press and hold
PRG(prg) key
for 2 seconds.
prg
Display will show ‘P2’ and flash.
To go to other parameters. Use
UP / DOWN keys.
3
Set Point
Function : To set the cutout point
of the controller.
Press & hold
SET key for 2
Seconds.
R1 will flash along with respective
setpoint1 for compressor 1.
The setpoint1 value can now be
changed by using the UP/DOWN
keys. After achieving the desired
value, press the set key and
you will see “- - -” which confirms
that the set point has been stored
in memory.
R2 will flash along with
respective set point 2 for
compressor 2. In the similar
manner use UP/DOWN key to
set the desired value and press
set key to confirm the settings.
Display will change to set point 1
and flash
Set Point 1 & 2
Min Max Fac
O
1.0 C
Set Point 1 & 2
Min Max Fac
O
1 C
O
P2-1 C
rS = 0
rS = 1
rS = Resolution
Set Parameter
P3
O
+1.0 C
P2
O
-1.0 C
O
P3+1 C
SZ-7552-P
www.pvrcontrols.com
INDIA
OPERATING
INSTRUCTIONS
DescriptionParameter Page
Set Point1 and set point 2.
To Set other parameters.
Controller for heating or cooling.
Max. High Temp Limit.
Min. Low Temp. Limit.
Differential.
Probe Calibration.
Time Delay.
To Start 2nd Comp. incase 1st Comp.
Min. Off time between two Comp.
Avoid over loading of Comp.
Keypad Lock.
Relay status on Probe Failure.
To set controller Resolution.
Factory set parameter.
End Programming.
Operating messages.
Technical data.
Suggested Wiring diagram.
Panel cutout & Dimensions.
P1
P2
P3
P4
P5
P6
t2
t3
t4
LP
E1
rS
FS
EP
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22-23

Sub-Zero SZ-7552-P Specifications

General

Type	Temperature Controller
Temperature Range	-58 to 302°F (-50 to 150°C)
Display	LED
Width	72 mm
Resolution	0.1°F
Input Type	Thermocouple (Type K)
Output Type	Relay (SPDT)
Height	2.83 inches (72 mm)

Summary

SZ-7552-P Controller General Description

General Description

Introduces the SZ-7552-P as a dual-compressor controller with separate setpoints, differentials, and time delays.

Setting the Cutout Point

Set Point Configuration

Details how to set the cutout point for compressor 1 and compressor 2 using the SET key and UP/DOWN keys.

Controller Parameter Configuration

P1 Parameter: Heating or Cooling Mode

Sets the controller for heating (1) or cooling (0) mode. T2 parameter is active only in cooling mode.

P2 Parameter: Maximum High Temperature Limit

Sets the maximum allowable high temperature limit, preventing set points from exceeding this value.

P3 Parameter: Minimum Low Temperature Limit

Sets the minimum allowable low temperature limit, preventing set points from dropping below this value.

P4 Parameter: Differential Settings

Configures the differential for set point 1 and set point 2 for compressor cycling.

P5 Parameter: Probe Calibration

Allows calibration of the temperature probe to compensate for potential offsets.

P6 Parameter: Time Delay Between Relays

Sets the time delay between the restart of compressor 1 and compressor 2 to prevent simultaneous startups.

t2 Parameter: Second Compressor Activation Delay

To start the second compressor if the first cannot achieve the set point within a specified time.

t3 Parameter: Minimum Off Time Between Compressors

Sets the minimum off-time delay between switching off both compressors to avoid simultaneous shutdowns.

t4 Parameter: Compressor Load Balancing

Avoids overloading of either compressor by interchanging their roles based on time.

E1 Parameter: Relay Status on Probe Failure

Defines the relay behavior when a probe failure is detected.

LP Parameter: Keypad Lock

Locks the keypad to prevent tampering, allowing only viewing of parameters.

rS Parameter: Controller Resolution

Sets the controller's temperature resolution to either 0.1°C or 1°C.

FS Parameter: Restore Factory Defaults

Restores all parameters to their programmed factory default values.

EP Parameter: End Programming

Exits the programming mode and returns the controller to normal operation.

Operating Information and Technical Data

Operating Messages and Icon Status

Explains various display messages (Ht, Lt, PP) and icon statuses (R1, R2, LP).

Technical Data

Provides specifications such as housing, dimensions, power input, operating temperature, and accuracy.

Installation and Safety Guidelines

Suggested Wiring Diagram

Illustrates the wiring connections for the controller, compressors, and NTC probe.

Panel Cutout and Installation

Details panel cutout dimensions, mounting, and installation procedures for IP65 rating.

Controller Placement and Probe Installation

Guidelines for installing the controller and probe in suitable environments to ensure accurate readings.

Wiring and Maintenance Cautions

Provides crucial cautions for wiring, warnings against improper handling, and maintenance instructions.