Overview
What are Control Relays?
Control relays are electromagnetic switches used to manage the flow of electrical energy in low-power applications or to provide logic signals within an automated system. Unlike contactors, which handle high-power motor loads, control relays are primarily used to switch auxiliary circuits, pilot lights, or to provide isolation between a high-voltage system and a low-voltage controller like a PLC. These components are essential for creating interlocks, safety circuits, and signal amplification in industrial environments.
Main Manufacturers
Palm Parts Solution stocks a comprehensive range of control relays from industry-leading manufacturers, ensuring compatibility with both legacy and modern control architectures:
- Allen-Bradley: Specializing in rugged industrial relays for NEMA and IEC applications.
- ABB: Known for the NF and AF line of contactor relays with wide-range electronic coils.
- Siemens: Offering high-reliability SIRIUS 3RH series for synchronized switching.
- Schneider Electric: Featuring the versatile TeSys CA series and Zelio plug-in relays.
- Omron: A leader in high-density G2R and MY series plug-in relays.
- GE Fanuc: Providing integrated relay solutions for CNC and PLC logic.
- Bosch Rexroth: High-performance relays for hydraulic and motion control interfaces.
Popular Product Families
We supply specific series designed for high-cycle industrial use, including:
- Allen-Bradley 700-Series: Including the 700-CF, 700-HA, and 700-HL terminal block relays.
- Siemens SIRIUS 3RH: Specifically the 3RH21 series designed for high-density DIN-rail mounting.
- Schneider Electric TeSys CA2/CA3: Renowned for their reliability in global control standards.
- ABB NF Series: Featuring 4-pole and 8-pole configurations with AC/DC compatibility.
- Omron MY and G2R: The industry standard for plug-in blade and PCB-mount applications.
Selection Guide
Selecting the correct control relay involves four primary technical criteria:
- Coil Voltage: Verify if your control signal is 24VDC, 120VAC, or 240VAC.
- Contact Configuration: Determine the number of Normally Open (NO) and Normally Closed (NC) poles required.
- Current Rating: Ensure the contact rating (typically 5A to 10A) exceeds the connected load.
- Mounting Type: Choose between DIN-rail mount (fixed) or plug-in (socket-based) for easier maintenance and replacement.
Replacement & Compatibility
When migrating from legacy systems, cross-brand compatibility is often possible. For instance, many Allen-Bradley 700-HL terminal block relays are functionally identical to Schneider Electric Zelio RSL or Phoenix Contact PLC-RSC units. When replacing obsolete GE or older ABB series, it is critical to verify the physical dimensions, as modern IEC relays often have a much smaller footprint than vintage NEMA designs.
1 product · GE Fanuc
Frequently asked questions
What is the difference between a control relay and a contactor?
A control relay handles low-current signals (typically under 10A) to switch logic or small loads, whereas a contactor is designed for high-power switching of motors and heavy inductive loads (often exceeding 600V and hundreds of amps). Control relays lack arc suppression features found in contactors.
What are the standard coil voltages for industrial control relays?
Most industrial control relays operate on 24VDC, 120VAC, or 230VAC. The 24VDC standard is most common in modern PLC-based systems like Allen-Bradley ControlLogix or Siemens S7-1500 to ensure safety and reduced electrical noise.
Can I add more contacts to an existing control relay?
Yes, many relays allow for the addition of auxiliary contact blocks (top or side mount) to increase the number of NO (Normally Open) or NC (Normally Closed) poles without replacing the entire unit. For example, the Schneider Electric TeSys CA2K series supports such expansions.
How do I find a replacement for an obsolete control relay?
To replace an obsolete relay, you must match the coil voltage, contact rating (Amps), and the mounting style (DIN rail or plug-in). Many Allen-Bradley 700-series relays can be cross-referenced to Schneider TeSys or ABB NF series, provided the physical footprint and contact configuration are compatible.
When should I use a Solid State Relay instead of an electromechanical relay?
An electromechanical relay (EMR) uses a physical coil and moving contacts, offering high voltage isolation and versatility. A Solid State Relay (SSR) uses semiconductors, which allow for high-speed switching and a longer lifespan due to the lack of moving parts, though they generate more heat.