Overview
Electronic contactors are now replacing traditional magnetic contactors in both manufacturing and spare parts for transport refrigeration systems. This change improves reliability, simplifies wiring, and reduces common failure points.
This technical bulletin explains the key differences between magnetic and electronic contactors, the new replacement part numbers, and the wiring changes technicians must follow during installation.
Why Electronic Contactors Are Being Introduced
Electronic contactors provide several improvements over older magnetic designs.
Key benefits include:
• Higher reliability by removing mechanical wear components found in magnetic contactors
• Simplified wiring with fewer auxiliary connections required
• Direct replacement compatibility for existing systems
• Improved electrical efficiency
Unlike older magnetic contactors, the new electronic versions are polarity-sensitive, meaning the positive and ground connections must be wired correctly.
Replacement Contactors for Magnetic Versions
The following electronic contactors replace the older magnetic versions used in transport refrigeration systems.
| Contactor Description | Old Magnetic Contactor P/N | New Electronic Contactor P/N |
|---|---|---|
| C30 Contactor (Right Auxiliary) | 10-00433-00 | 10-00503-31 |
| C30 Contactor (Left Auxiliary) | 10-00433-06 | 10-00503-32 |
| C30 Contactor (Right Auxiliary + T1 T2 T3 terminals at top) | 10-00433-07 | 10-00503-31 |
| C7 Contactor (Right Auxiliary) | 10-00433-05 | 10-00503-41 |
These new electronic versions act as direct replacements for the magnetic contactors previously installed in many refrigeration units.
Important Installation Changes
When replacing a magnetic contactor with the new electronic version, technicians will notice several wiring differences.
Magnetic Contactors (Old Design)
Older magnetic contactors included:
• A B1 terminal used for the starting coil
• A black auxiliary wire connecting B1 to the auxiliary terminal
• A separate wire connecting A1 to the top auxiliary terminal
Electronic Contactors (New Design)
The new electronic contactors simplify this arrangement.
Key differences include:
• No B1 terminal
• No top or bottom auxiliary terminals
• Auxiliary black wires are no longer required
During installation, any black auxiliary wires used on the previous magnetic contactor should be removed and discarded.
This simplifies the wiring layout and reduces potential failure points in the system.
Polarity Requirements for Electronic Contactors
Unlike magnetic contactors, electronic contactors are polarity-sensitive.
This means the positive supply and ground must be connected to the correct terminals on the contactor.
Correct wiring requires:
• +12V connected to the positive terminal
• Ground connected to the ground terminal
Incorrect polarity can prevent the contactor from operating correctly and may cause system faults.
Electrical Diagram Reference
When installing the electronic contactor, technicians should follow the polarity shown in the electrical diagram.
Key diagram references:
• E = Electronic Contactor
• A1 / A2 terminals identify the correct polarity connections
• PSCON1 / PSCON2 correspond to the system contactor connections in the wiring diagram.
Always verify the correct wiring configuration before powering the system.
Technical Support
If you require assistance selecting replacement contactors or verifying compatibility with your refrigeration unit, the Myriad technical team can help.
Browse available contactor replacements or contact Myriad for further support.