Best Single Phase Overload Relay Options for Control Panels
Single-phase overload relays protect motors and equipment from overheating and phase faults. This guide highlights five reliable options suited for different applications, from compact HVAC controls to industrial motor starters. Best for replacement in TeSys D or CJX-style panels, these relays help ensure safe, automatic protection and straightforward wiring. The top picks cover simple thermal overloads, voltage monitoring, and solid-state alternatives. Use the buyer tips below to match your needs to the right product.
| Product | Type / Best For | Key Benefit |
|---|---|---|
| Square D Overload Relay LRD21 | Single-phase protection | Sensitive trip range 12A–18A |
| Square D LRD07 Overload Relay | Compact motor protection | TeSys D compatible, 1.6–2.5A |
| GEYA GRV8-01 Single Phase Voltage Relay | Voltage monitoring | True RMS, adjustable operation |
| Schneider Electric DPER07 Easy TeSys Thermal Relay | HVAC/industrial motors | Manual/Auto reset, 690V/4000Hz rated |
| CGELE SSR-40AA Solid State Relay | Solid-state relay option | 70-250VAC input, 24-480VAC output |
Square D Overload Relay LRD21
The Square D LRD21 overload relay provides single-phase protection with a defined trip range. Best for small to mid-size motor circuits using TeSys D contactors. It targets applications where a precise trip current is required to prevent motor burnouts in light industrial setups.
Best for: technicians seeking a straightforward, compatible relay for TeSys D systems with predictable trip behavior. Why selected: widely used in standard control panels, easy to source, and designed for single-phase protection. Limitation: verify compatibility with your contactor frame and terminal layout before ordering.
Square D LRD07 Overload Relay
The LRD07 model is a compact overload relay designed for single-phase protection with a 1.6A to 2.5A trip class. It fits neatly under compact motor starters and is suitable for tighter control panels or limited mounting space.
Best for: space-constrained panels needing reliable, quick-install protection. Why selected: small footprint, easy integration with TeSys D contactors. Caution: ensure the contactor frame size matches the relay’s current range to avoid mis-sizing.
GEYA GRV8-01 Single Phase Voltage Relay
The GEYA GRV8-01 is a single-phase voltage relay with true RMS voltage measurement and adjustable operation mode. It is ideal for circuits where monitoring supply voltage is critical to protect motors from undervoltage or overvoltage conditions.
Best for: applications needing active voltage supervision alongside motor protection. Why selected: precise voltage sensing and user-adjustable thresholds. Caution: verify the voltage range and control wiring for your system to ensure reliable operation.
Schneider Electric DPER07 Easy TeSys Thermal Relay
The DPER07 thermal overload relay offers a compact, modular design for space-conscious installations. It is suited for 3-phase motor protection in HVAC, pumps, and compressors when paired with appropriate contactors. It supports manual or automatic reset and a broad insulation rating.
Best for: space-limited panels needing a modular, configurable overload solution. Why selected: durability and easy field wiring for HVAC and industrial applications. Caution: confirm compatibility with your chosen contactor and mounting base to ensure proper fit.
CGELE SSR-40AA Solid State Relay
The CGELE SSR-40AA is a solid-state relay suitable for AC-to-AC control with a broad input and output range (70-250VAC input, 24-480VAC output) and a 40A rating. This option reduces mechanical wear and can provide fast switching in motor control circuits.
Best for: upgrades to solid-state switching in motor circuits with limited maintenance. Why selected: eliminates mechanical contacts and offers fast, silent operation. Caution: SSRs generate different heat profiles; ensure adequate cooling and proper heat sinking in your panel.
Buying Guide: Key Considerations For Single-Phase Overload Relays
- Protection target: Decide whether you need pure overload protection, voltage monitoring, or a combined approach. Voltage-relay options help prevent damage from undervoltage or overvoltage, while thermal relays protect against overheating.
- Contactor compatibility: Check the relay’s frame size and mounting compatibility with your current contactor model (for example, TeSys D or CJX-series) to ensure a proper fit.
- Current and trip settings: For thermal relays, confirm the adjustable current range matches your motor’s full-load current. For voltage relays, verify the adjustable thresholds suit the supply in your facility.
- Rated voltage and insulation: Review insulation voltage ratings to ensure compatibility with your system’s voltage class (AC 110–240V, 690V, etc.).
- Mounting and space: If panel space is tight, prioritize compact, modular designs that fit under existing contactors or DIN rails.
- Maintenance and resets: Decide between manual and automatic reset options. Manual reset provides deliberate restart control, while automatic reset offers faster recovery after a fault (consider safety implications).
- Heat management: For solid-state relays, ensure adequate cooling as they can generate heat at higher currents. Include heat sinks if necessary in the enclosure.
- Diagnostics and indicators: Choose relays with clear trip indicators or test functions to simplify commissioning and troubleshooting.
Frequently Asked Questions
- What is a single-phase overload relay used for?
It protects motors and equipment by disconnecting power when the motor draws excess current or experiences overload conditions. - When should I choose a voltage relay over a thermal overload relay?
Use a voltage relay when supply voltage fluctuations threaten motor health; opt for a thermal overload relay for direct motor current protection. - Are solid-state relays compatible with all motors?
SSRs are compatible with many motors but require proper heat management and compatible control signals; always verify the load current and heat dissipation needs. - How do I verify relay compatibility with my contactor?
Check the relay’s current rating, mounting style, and the contactor’s coil and terminal layout to confirm fit. - Can these relays protect three-phase motors as well?
Some relays are designed for single-phase protection; others support three-phase configurations. Verify the product’s documentation for phase compatibility. - Do these relays come with installation accessories?
Some listings include mounting hardware or connectors; refer to the product page for included items and consider purchasing a compatible base or DIN rail if needed.