Johnson Controls A350A/B Data Sheet

FANs 930, 930.5, 125, 121

Product/Technical Bulletin A350

Issue Date 0614

System 350™

A350A/B Electronic Temperature Control

The A350A/B Series is an on/off electronic temperature control with a Single-Pole, Double-Throw (SPDT) relay output and a Light-Emitting Diode (LED) relay status indicator. Designed to operate with both heating and cooling equipment, this control includes an adjustable differential and an interchangeable temperature sensor.

As are all System 350™ products, the A350A/B is housed in a NEMA 1, high-impact plastic enclosure. The modular design provides easy, plug-together connections for quick installation and future expandability.

	Figure 1: A350 Series Electronic
	Temperature Control
Features and Benefits
 Modular Design	Enables stage, display, and power modules to
	be purchased and installed as needed
 Plug-together Connectors	Eliminates wiring between modules and
and 35 mm DIN Rail	reduces installation costs
Mounting
 Two Standard Models	Reduces inventory by encompassing
Cover Wide Setpoint	temperature ranges required to support the
Ranges	majority of Heating, Ventilation, Air
-30 to 130°F (-34 to 55°C) or	Conditioning, and Refrigeration (HVAC/R)
90 to 250°F (32 to 121°C)	applications
 Wide Adjustable Differential	Enables the user to match equipment cycle
of 1 to 30F° (0.6 to 16.7C°)	rate and/or sequencing for a given application
 Field-Selectable Mode	Operates in both heating and cooling
Jumpers	applications
 Available with Either	Helps deter accidental and unauthorized
External or Concealed	adjustments
Setpoint
 Interchangeable	Increases versatility and serviceability
Temperature Sensors

© 2014 Johnson Controls, Inc.	1
Part No. 24-7664-44, Rev. D	www.johnsoncontrols.com
Code No. LIT-930010

Application

The A350A/B Temperature Control can be used as a standalone device or in conjunction with other

System 350 plug-together modules to control single or multiple-stage HVAC or refrigeration equipment. Typical applications include:

frozen/refrigerated food cases

cooling tower control

beverage/milk coolers

chiller staging

space temperature control

A typical System 350 Temperature Control arrangement includes the following:

A350A/B Temperature Control

S350 Stage Modules

D350 Digital Temperature Sensor/Setpoint Display Module

Y350R Power Module (or Class 2 24 VAC transformer)

A99B Series Temperature Sensor

IMPORTANT: Use this A350A/B Electronic Temperature Control only as an operating control. Where failure or malfunction of the A350A/B control could lead to personal injury or property damage to the controlled equipment or other property, additional precautions must be designed into the control system. Incorporate and maintain other devices, such as supervisory or alarm systems or safety or limit controls, intended to warn of or protect against failure or malfunction of the A350A/B control.

IMPORTANT: Utiliser ce A350A/B Electronic Temperature Control uniquement en tant que dispositif de régulation. Lorsqu'une défaillance ou un dysfonctionnement du

A350A/B control risque de provoquer des blessures ou d'endommager l'équipement contrôlé ou un autre équipement, la conception du système de contrôle doit intégrer des dispositifs de protection supplémentaires. Veiller dans ce cas à intégrer de façon permanente d'autres dispositifs, tels que des systèmes de supervision ou d'alarme, ou des dispositifs de sécurité ou de limitation, ayant une fonction d'avertissement ou de protection en cas de défaillance ou de dysfonctionnement du

A350A/B control.

2 System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin

Operation

The A350A/B Temperature Control operates on

24 VAC and provides an SPDT relay output. A front panel LED lights to indicate when the relay is energized. Adjustable features include:

setpoint

differential

heating/cooling mode

IMPORTANT:	All System 350 Controls are
	designed for use only as
	operating controls. Where an
	operating control failure would
	result in personal injury and/or
	loss of property, it is the
	responsibility of the installer to
	add devices (safety, limit controls)
	that protect against, or systems
	(alarm, supervisory systems) that
	warn of, control failure.

Setpoint Adjustment

Setpoint is defined as the temperature at which the A350A/B’s relay de-energizes. Use the Setpoint Dial on the front of the A350A/B to adjust setpoint. See Figure 2.

Differential Adjustment

Differential is defined as the change in sensor temperature between energization and deenergization of the relay. Adjustment of the A350A/B differential is made using the potentiometer marked DIFF. See Figure 2 for its location. Refer to Table 5 for adjustment ranges.

24V
COM	Setpoint
VDC
	Dial
SEN
		Module
		Connector
DIFF
(Differential		Jumper Block
Potentiometer)
Relay		Position
		Heating
LED Indicator	Relay
		Cooling

NC NO

Figure 2: A350A/B Board Layout and

Terminal Locations

Heating/Cooling Mode Adjustment

With Heating mode selected, the differential is below setpoint. The relay and LED indicator will de-energize as the temperature rises to the setpoint. As the temperature drops to the setpoint minus the differential setting, the relay will energize and the LED illuminates. Refer to Figure 6.

With Cooling mode selected, the differential is above setpoint. The relay and LED indicator will de-energize as the temperature drops to setpoint. As the temperature rises to the setpoint plus differential setting, the relay will energize and the LED illuminates.

As shipped from the factory, the heating/cooling jumper blocks are installed in the horizontal (cooling) position. See Figure 2.

System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin 3