Murphy A20 Series Magnetic Switch, Pre-Alarm Using A20/A25TABS, Typical Internal Wiring Diagrams

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Magnetic Switch

INDUCTIVE AND HIGH CURRENT LOADS REQUIRE THE USE OF A MAGNETIC SWITCH. The SWICHGAGE® contacts are for light-duty elec- trical switching to operate alarms or control devices. Murphy manufactures the Magnetic Switch for protection of the pilot-duty SWICHGAGE® limit contacts.

TATTLETALE® Magnetic Switches show the cause of shutdown for applica- tions that include: capacitor discharge or magneto ignitions, battery systems and electric motor driven equipment. Typical wiring diagrams are shown below.

A20T Temperature

117 Magnetic Switch

SWICHGAGE®

 

 

 

 

HIGH

C

S

B

C

N. O.

 

 

 

Energized To Run Devices

 

_

+

 

Battery

A20P Pressure

A20T Temperature

518PH TATTLETALE®

 

SWICHGAGE®

 

SWICHGAGE®

 

 

 

 

 

 

R

LOW

 

 

HIGH

G NC SW1 SW2 B

 

 

 

 

 

 

N.O. SWICHGAGE®

 

 

N. C.

C

instruments

C

N. O.

 

 

 

 

_

+

Energized To Run Devices

Battery

N.C. switches option

 

 

Pre-Alarm Using A20/A25TABS

The A20TABS and A25TABS features a standard limit contact for equipment shutdown on high temperature. It also has an internal SPDT snap-switch to sig- nal an alarm before shutting down. When the snap-switch trips (preset point), on rising temperature, the switch completes a circuit to activate an alarm. If the temperature continues to increase, the face-adjustable pointer contact will make

and the shutdown circuit will be completed (see the typical diagram below for reference). The front contact shutdown limit setting (which is adjustable) and the snap-switch are preset at the factory. Refer to “Temperature Ranges and Factory Settings” table on opposite page for settings. For alternative alarm before shutdown, see Magnetic Switch model 760A or 761APH.

Alarm Before

 

A20TABS

 

Shutdown

 

®

 

SWICHGAGE

MINI-SIREN®

 

 

 

 

 

 

 

 

G

ABS

 

HIGH

 

N. C.

C

N. O.

 

Shutdown Device

 

Opens circuit to

or Ignition Circuit

 

shutdown engine.

518PH

TATTLETALE®

R

NC SW1 SW2 B

_

+

 

Battery

Typical Internal Wiring Diagrams

Pointer shown in the shelf position. Pointer type contact rating: pilot-duty 2 A @ 30 VAC/VDC resistive.

Snap-acting switch rating: 3 A @ 30 VDC inductive. 4 A @ 125 VAC inductive.

A20T

A20T-HL

A20TABS

A20TE

HIGH

LOW

HIGH

ABS

HIGHRESET

SET

N. C. C N. O.

N. C. C

N. O.

N. C. C N. O.

N. C. C N. O.

A25T

A25T-HL

A25TABS

A25TABS-HL

A25TE

N. C. C

N. O.

N. C. C

N. O.

N. C. C

RESET

N. O.

N. C.

SET

RESET

C

N. O.

N. C. C

N. O.

 

SET

RESET

SET

 

 

HIGH

LOW

 

 

HIGH

 

HIGH

LOW

 

 

HIGH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L

P

H

L

P

H

L

P

H

L

P

H

L

P

H

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Contents Coolant or Oil Temperature Cylinder Head TemperatureGage-Only Models Maximum Temperature DimensionsTemperature Ranges and Factory Settings Temperature Accuracy ChartMagnetic Switch Pre-Alarm Using A20/A25TABSTypical Internal Wiring Diagrams Warranty How to Order

A25 Series, A20 Series specifications

The Murphy A20 Series and A25 Series are two advanced engine control and monitoring systems designed to optimize performance and enhance the productivity of various applications. Both series are recognized for their robust construction, user-friendly interfaces, and comprehensive functionalities, making them ideal choices for demanding industrial environments.

The A20 Series is particularly notable for its affordability and flexibility. This system is engineered to integrate seamlessly with various engine types and monitoring setups. It features a lightweight design, making it perfect for applications where space is a premium. Key characteristics include customizable screens, allowing operators to configure display parameters according to specific needs. The A20 Series is equipped with a wide range of sensors that monitor critical engine functions like oil pressure, temperature, fuel level, and engine RPM. With advanced alarm capabilities, it enables users to respond promptly to potential issues, thus safeguarding the engine and prolonging its operational lifespan.

On the other hand, the Murphy A25 Series offers enhanced capabilities tailored for more complex applications. It boasts a more extensive display, providing a clearer interface for monitoring multiple parameters simultaneously. The A25 Series also supports robust data logging features, which are invaluable for maintenance and analysis purposes. Users can access historical data to identify trends and troubleshoot issues effectively. The A25's built-in communication protocols allow for easy integration with existing control systems, thereby enhancing flexibility and ease of use.

Both series incorporate cutting-edge technologies to improve reliability and performance. Engineered with high-quality materials and advanced electronics, they operate effectively in challenging environments. These systems are designed to function in varying temperatures and humidity levels, ensuring consistent performance under fluctuating conditions.

In conclusion, the Murphy A20 and A25 Series represent a significant advancement in engine monitoring technology. While the A20 Series is ideal for simpler applications requiring flexibility and ease of use, the A25 Series caters to those needing advanced monitoring and data logging capabilities. Together, these systems provide powerful tools for enhancing engine efficiency, safety, and operational longevity, making them essential components in modern industrial applications. Whether for construction, agriculture, or other heavy-duty landscapes, Murphy's innovative solutions stand out for their reliability and performance.
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