Littelfuse HRDI421 - The HRDI Series combines an electromechanical relay output with microcontroller timing circuitry. It offers 12 to 230V operation in five ranges and factory fixed, external, or onboard adjustable time delays with a repeat accuracy of ±0.5%. The output contact rating allows for direct operation of heavy loads, such as compressors, pumps, blower motors, heaters, etc. This series is ideal for OEM applications where cost is a factor. Operation (Interval): Upon application of input voltage, the time delay begins. The output relay is energized during the time delay. At the end of the time delay, the output de-energizes and remains de-energized until input voltage is removed. Reset: Removing input voltage resets the time delay and the output.
Littelfuse

HRDI421

Alternate Item Number: HRDI421

UPC: 079458993851

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Overview

The Littelfuse HRDI421 is a cost-effective electromechanical time delay relay designed for OEM applications, featuring integrated microcontroller timing circuitry for precise control. This versatile relay operates across a wide voltage range of 12 to 230V AC/DC, supporting five distinct ranges for global compatibility. The HRDI421 offers flexible timing adjustments, including factory-fixed, external adjustment via the panel-mountable Versa-Pot (P1004-95), or onboard potentiometer control. All timing options deliver exceptional repeat accuracy of ±0.5%. Its robust, isolated 30A SPDT normally open output contact rating allows for direct switching of heavy industrial loads such as compressors, pumps, blower motors, and heaters, eliminating the need for additional contactors or relays. The encapsulated design provides superior protection against shock, vibration, and humidity, ensuring reliable operation in harsh industrial environments. Factory calibration ensures ±2% accuracy, while the microcontroller-based timing guarantees consistent performance across temperature variations. The HRDI421 operates in an interval mode: upon application of input voltage, the time delay begins, and the output relay energizes. At the end of the programmed delay, the output de-energizes and remains so until input voltage is removed. Removing input voltage also resets the time delay and the output. Ideal for OEM applications where cost efficiency and space are critical, the HRDI421 measures approximately 2.25" x 1.5" x 1.25" (57.2mm x 38.1mm x 31.8mm) and is easily mountable on DIN rails or via optional mounting brackets (P1023-6). Available accessories include the Versa-Knob (P0700-7) for manual adjustment, female quick-connect terminals (P1015-13/P1015-64) with strain relief, and quick-connect to screw adapters (P1015-18) for enhanced wiring flexibility. Built on the reliable 380-series heritage, the HRDI421 provides dependable, accurate timing for industrial automation.
  • Microcontroller-based timing with ±0.5% repeat accuracy
  • 12 to 230V operation across five ranges
  • Isolated 30A SPDT, NO output contacts for heavy loads
  • Encapsulated design for shock, vibration, and humidity protection
  • Compact, low-cost design ideal for OEM applications

Specifications

Brand Name
Littelfuse
Mounting
Surface mount with one #10 (M5 x 0.8) screw Mount
Number Of Poles
Surface mount with one #10 (M5 x 0.8) screw
Operating Temperature
-40 to 60 F
Operating Temperature, Maximum
60 F
Operating Temperature, Minimum
-40 F
Special Features
10Y WARR
Standard
CE/UR/CSA
Sub Brand
SSAC

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Frequently Asked Questions

What technical support resources does Littelfuse offer?

Littelfuse offers a Techline with technical experts who can provide product cross references, general technical information, engineering drawings, and application assistance. They can be contacted at 1-800-TEC-FUSE or [email protected].

How can distributors access Littelfuse product information?

Distributors can access product information through the Littelfuse Business Center website, which provides product availability, pricing, order placement, order status, special pricing agreements, literature ordering, and technical resources.

What technical support resources does Littelfuse offer?

Littelfuse offers a Techline with technical experts who can provide product cross references, technical information, engineering drawings, and application assistance. They can be contacted at 1-800-TEC-FUSE or [email protected].

What types of industrial protection products does Littelfuse offer?

Littelfuse provides a comprehensive range of industrial protection products including fuses, fuse holders, protection relays, voltage monitors, motor protection devices, ground-fault protection relays, and arc-flash protection relays.

What marketing support does Littelfuse provide to distributors?

Littelfuse offers a Marketing to Marketing program that includes co-branded email campaigns, content sharing, marketing tool training, product launch support, and website linking. The program is free and aims to help distributors grow sales.

What training resources are available for Littelfuse products?

Littelfuse University provides in-depth training courses ranging from 3 to 20 minutes, covering basic to expert levels across various product focus areas. Courses can be accessed at LittelfuseUniversity.com.

How can I access Littelfuse product information and sales tools?

Littelfuse provides multiple digital resources including Littelfuse University for training, a digital asset portal for marketing materials, RepFiles mobile app for product information, and the Littelfuse Business Center website for product availability, pricing, and ordering.

What types of digital marketing assets does Littelfuse provide?

Littelfuse offers a digital asset portal with online sales tools, product and application images, video files, sales presentations, webcast recordings, and product literature that can be downloaded.

What marketing support does Littelfuse provide to distributors?

Littelfuse offers a Marketing to Marketing program that includes co-branded email campaigns, content sharing, marketing tool training, product launch support, and website linking. The program is free and aims to help distributors grow sales.

How can distributors participate in Littelfuse's promotional programs?

Distributors can access Promotional Allowance Programs for demand generation campaigns, sales incentives, joint email campaigns, trade shows, and other brand awareness activities. Activities must be pre-approved at least 30 days in advance.

Frequently Asked Questions about Littelfuse

What certifications and standards do Littelfuse products comply with?

Littelfuse products are certified to multiple international standards, including UL (Underwriters Laboratories), CSA (Canadian Standards Association), CCC (China Compulsory Certification), and EAC (Eurasian Conformity). Customers can verify specific product certifications by consulting individual product datasheets on Littelfuse.com, which provide comprehensive details about standards compliance for each component.

What industries and applications are Littelfuse products used for?

Littelfuse products are critical for electrical protection and safety across multiple industrial sectors, including manufacturing, automation, power distribution, and electrical control systems. Their comprehensive product portfolio serves industries that require robust electrical protection, including motor and pump applications, solar installations, programmable logic controllers (PLCs), electrical switch panels, and critical infrastructure environments. Key product lines protect against overcurrent, voltage transients, ground faults, and temperature-related electrical risks, ensuring equipment safety and operational reliability.

What technical support does Littelfuse offer?

Littelfuse offers comprehensive technical support through multiple channels. Their Technical Hotline (800-TEC-FUSE) provides direct access to engineers who can help identify issues and recommend solutions. Additionally, Littelfuse offers extensive online Technical Resources at Littelfuse.com, including datasheets, product manuals, whitepapers, application guides, and online design tools. Their experienced product and application engineers also provide step-by-step support from design to installation.

What are the main product lines offered by Littelfuse?

Littelfuse offers comprehensive industrial protection and control product lines, including fuses, fuse holders, protection relays, temperature sensors, and electrical safety components. Their key product categories span surge protective devices, custom OEM products, electrical switch panels, medium voltage fuses, ground-fault protection relays, motor and pump protection devices, and temperature sensors. These products are designed to minimize electrical safety hazards, limit equipment damage, improve productivity, and safeguard personnel from electrical faults.

What are the key features of Littelfuse products?

Littelfuse products feature exceptional circuit protection technologies with key characteristics including UL/IEC safety standard compliance, low internal resistance, and advanced protective capabilities across multiple product lines. Their components provide critical protection for industrial systems, offering features like overcurrent protection, voltage transient suppression, and resettable protection devices with ultra-low resistance and compact designs. Key product lines include fuses, metal oxide varistors (MOVs), TVS diodes, PolySwitch devices, and specialized electronic protection components that enhance system reliability and safety.

What environmental ratings do Littelfuse products have?

Littelfuse products feature comprehensive environmental ratings, including NEMA Type 1, 2, 3, 3R, 4/4X, 12, and 13 certifications, as well as IP65 protection. These ratings ensure superior protection in diverse industrial environments, with an operating temperature range of -40°F to +131°F (-40°C to +55°C). Many products also include UV-stabilized materials and neoprene gaskets for enhanced durability in outdoor and challenging conditions.

What accessories are available for Littelfuse products?

Littelfuse offers several key accessories across their product lines, including fuse holders, voltage monitoring modules, and terminal connectors. Specific accessories include the LPSM003ZXID (indicating) and LPSM003Z (non-indicating) POWR-SAFE Dead Front fuse holders for Class CC and Midget-Style fuses, the VRM6048 voltage monitor accessory module, and female quick connect terminals (P1015 series) in various wire gauge sizes. These accessories are designed to enhance protection, monitoring, and connectivity for Littelfuse electrical components.

What is Littelfuse's warranty policy?

Littelfuse provides comprehensive warranty details on their official website at www.littelfuse.com/warranty. Customers should visit this page to review the specific warranty terms and conditions for their specific product lines. For direct warranty support or questions, customers can contact Littelfuse Technical Support at 1-800-TEC-FUSE or email [email protected].

What communication protocols do Littelfuse products support?

Littelfuse supports a comprehensive range of industrial communication protocols, including PROFIBUS, PROFINET, EtherNet/IP, DeviceNet, Modbus RTU, and CANopen. Our products provide flexible connectivity solutions across multiple industrial automation platforms, enabling seamless integration with various control systems and network architectures.

How are Littelfuse products typically installed?

Littelfuse products are typically installed using specialized mounting hardware like fuse holders, blocks, and panels designed for specific industrial applications. The POWR-SAFE Dead Front holders, for example, provide optimum protection for Class CC and Midget-Style fuses, supporting installations up to 600 VAC/DC. Installation often involves using precision terminals with strain relief, such as 0.25 in. female quick connect terminals, to ensure secure and safe electrical connections in industrial control systems.