Thermal overload heaters and relays are essential for safeguarding motors in HVAC systems, pumps, and compressors. This guide highlights five reliable options from reputable brands, focusing on overload protection, reset options, and compatibility with common electrical standards. Each product section includes key features to help compare capabilities and select the right device for reliable motor protection.
| Product | Brand |
|---|---|
| Schneider Electric DPER07 Easy TeSys Thermal Overload Relay | Schneider Electric |
| Walfront NR2-36 Electric Heat Thermal Overload Relay | Walfront |
| Schneider Electric DPER21 Easy TeSys Thermal Overload Relay | Schneider Electric |
| Schneider Electric DPER12 Easy TeSys Thermal Overload Relay | Schneider Electric |
| New Square D Thermal Overload Heater Element Unit B28 / B-28 | Square D |
Schneider Electric DPER07 Easy TeSys Overload Relay
This TeSys thermal overload relay is designed for protection of 3-phase motors in HVAC, heat pumps, compressors, and similar equipment. It supports a network frequency range up to 4000 Hz, with rated insulation at 600V cUL / 690V IEC, and a tripping class of 10. The unit features a compact, modular design that fits space-constrained installations and can be quickly configured to match a specific application. It offers a reliable, cost-effective solution to guard motors against overloads, phase failures, and phase unbalances while resisting dust and environmental exposure.
Walfront NR2-36 Thermal Overload Relay
The Walfront NR2-36 electric heat thermal overload relay is designed to protect motors effectively in 50-60 Hz circuits and supports an insulation voltage up to 690V, making it broadly compatible with many industrial and commercial motor systems. Its durable construction is intended for long-lasting performance, with a temperature-compensation mechanism to improve accuracy during overload events. This device helps prevent motor damage by accurately detecting overload conditions and cutting power before motor wear accumulates.
Schneider Electric DPER21 Easy TeSys Overload Relay
The DPER21 model from Schneider Electric provides manual or automatic reset options and a screw clamp terminal design for secure wiring. It is suitable for protecting 3‑phase motors in HVAC systems, pumps, and compressors, with a robust 0-4000 Hz network frequency compatibility and insulation ratings of 600V cUL / 690V IEC. The compact, modular form allows quick integration into tight spaces, delivering dependable overload protection while minimizing downtime and maintenance complexity.
Schneider Electric DPER12 Easy TeSys Overload Relay
This DPER12 overload relay shares the same protection philosophy as its siblings, offering a compact, modular design with manual/automatic reset and screw clamp terminals. It is designed for use with 3-phase motors in HVAC and related equipment, rated for 0-4000 Hz network frequency and insulation up to 600V cUL / 690V IEC. The unit supports quick configuration to suit various motor protection scenarios and provides reliable performance in dusty or challenging environments.
New Square D Thermal Overload Heater B-28
The Square D B-28 thermal overload heater unit is a compact solution with an emphasis on reliable motor protection. It offers a practical option for replacements or upgrades in systems using B28-rated heaters, ensuring continuity of operation for fans, pumps, and HVAC compressors. The unit’s weight and dimensions make it easy to install in existing panels or enclosures, delivering dependable performance without occupying excessive space.
Buying Guide: Key Purchase Considerations
- Motor compatibility: Confirm the relay or heater’s amperage rating, insulation voltage, and phase configuration (single vs. three-phase) to match your motor and system requirements.
- Reset behavior: Decide between manual or automatic reset based on how quickly you want the system to recover after an overload and the risk tolerance for restart cycles.
- Environmental protection: Look for compact, dust-resistant designs for harsh environments, and check enclosure ratings if the unit will be exposed to humidity or debris.
- Electrical standards: Verify insulation ratings (e.g., 600V cUL, 690V IEC) and frequency compatibility (0-4000 Hz is common for TeSys-style relays) to ensure compliance with local codes and equipment.
- Installation and wiring: Favor models with screw clamp terminals and modular designs for easier wire routing, faster installation, and future upgrades.
- Brand and support: Choose established brands (Schneider Electric, Square D, Walfront, etc.) for better tech support, documentation, and parts availability.
- Maintenance considerations: Some relays offer built-in temperature compensation, which can improve accuracy and extend motor life in fluctuating operating conditions.