Best Solid State Overload Relays for Industrial Control and Refrigeration
Solid state overload relays protect three-phase motors from damage due to overcurrent, overheating, and startup surges without the need for traditional heater elements. This guide highlights five top options, covering adjustable trip classes, frame sizes, and 3-phase compatibility. Explore how these relays balance reliability, ease of use, and performance in demanding environments.
Summary of Selected Products
| Product | Brand | Key Feature | Trip Classes |
|---|---|---|---|
| Siemens 3UB81234EW2 | Siemens | Solid State Electronic Overload, DIP-switch trip class selection | 5/10/20/30 |
| Supco PRO41 | Supco | Push-On Relay and Overload Combination | Single class selectable by model |
| BlueStars RCO210 | BlueStars | 3-in-1 hard-start with relay and overload | Not specified on listing |
| Siemens 3UB81234DW2 | Siemens | Solid State Overload with adjustable trip classes | 5/10/20/30 |
| Siemens 3UB81334GW2 | Siemens | High current solid state overload, adjustable via DIP | 5/10/20/30 |
Siemens 3UB81234EW2 Solid State Overload Relay
Siemens MLFB 3UB81234EW2 (Catalog No. 48ATE3S00) targets 10 to 40A with frame size A1 for 3-phase systems. It features selectable trip classes of 5, 10, 20, or 30 via DIP-switches and uses a solid-state electronic overload, eliminating the need for heaters. This design supports automatic or manual reset, enabling flexible protection schemes in industrial drives and motor control centers. Its compact form suits tight installations while maintaining robust protection across common motor ratings. Compatible with MES/ESP200 configurations, this relay is designed for applications where rapid, reliable trip signaling matters.
Siemens 3UB81234DW2 Solid State Overload Relay
The Siemens 3UB81234DW2 (Catalog No. 48ATD3S00) covers 5.5 to 22A with a frame size A1 for 3-phase systems. It supports configurable trip classes via DIP-switches and employs a solid-state overload that eliminates the need for heater elements. The device provides manual or automatic reset options for versatile protection in motor drives, compressors, and pump systems. This option is suitable where compact, scalable protection is needed and where electric motor startups demand precise current limitation.
Siemens 3UB81334GW2 Solid State Overload Relay
The Siemens 3UB81334GW2 (Catalog No. 48BTG3S00) is designed for 25 to 100A with a 3-phase setup and a frame size B. It offers adjustable trip classes (5/10/20/30) via DIP-switches and a solid-state overload without heaters, plus manual/automatic reset. This unit is well-suited for higher-current applications needing tight protection and dependable shutdown behavior when overcurrent or overheating is detected in industrial motors and drives.
BlueStars RCO210 3-in-1 Hard Start Capacitor Replacement
The RCO210 combines a solid state relay overload with a start capacitor in a 3-in-1 module for refrigeration and other frequently-started motors. It includes a 243 to 292 MFD start capacitor and a maximum continuous running load of about 13.3A, operating at 115V. Quick-connect mounting and compatibility with 110-125VAC appliances make it suitable for replacing multiple components in one step, potentially reducing electrical clutter and installation effort. This unit supports auxiliary start boost for improved cold-weather or high-load starts.
Poweka 2 Pack RCO210 3-in-1 Solution
Poweka offers a two-pack of the RCO210 3-in-1 hard-start relay, overload, and start capacitor combination. Compatible with 1/12 hp to 1/2 hp compressors and designed for 120V operation, these units help extend compressor life and improve efficiency by aiding startup. The 3-in-1 design simplifies installations by replacing separate relays, overloads, and start capacitors in many refrigeration and HVAC systems, with emphasis on improving startup reliability and energy efficiency.
Buying Guide: Key Considerations For Solid State Overload Relays
- Current rating and frame size: Ensure the relay supports the motor current and fits the control panel layout. Higher current units may require larger enclosures and proper heat management.
- Trip class options: Look for adjustable trip classes (5/10/20/30) to tailor protection to motor characteristics and startup surges. DIP-switch or software configuration can affect installation time.
- Reset behavior: Manual vs. automatic reset modes affect restart procedures after trips. Automatic reset may restore operation sooner but could mask underlying faults if not monitored.
- Solid-state vs. thermal overload: Solid-state relays eliminate heater elements and provide faster responses but may require proper heat dissipation and EMI considerations in noisy electrical environments.
- Compatibility: Verify 3-phase compatibility, voltage range (e.g., 115V to 230V), and any required control interfaces with existing drives or contactors.
- Installation and wiring: Check mounting options, lead lengths, and whether a 3-in-1 module (relay, overload, and capacitor) is appropriate for simplifying the wiring in refrigeration or HVAC circuits.
- Reliability and diagnostics: Consider relays with status indicators or fault signaling to simplify maintenance and fault isolation in industrial settings.
- Manufacturer support and documentation: Access to catalogs, part numbers, and installation guides helps ensure correct selection and troubleshooting.