Littelfuse KRDM121 - The KRDM Series is a compact time delay relay measuring only 2 in. (50.8 mm) square. Its solid-state timing circuit provides excellent repeat accuracy and stability. Encapsulation protects against shock, vibration, and humidity. The KRDM Series is a cost effective approach for OEM applications that require small size, isolation, reliability, and long life. Operation (Delay-on-Make): Upon application of input voltage, the time delay begins. The output is de-energized before and during the time delay. At the end of the time delay, the output relay energizes and remains energized until input voltage is removed. Reset: Removing input voltage resets the time delay and output.
Littelfuse

KRDM121

Alternate Item Number: KRDM121

UPC: 079458994759

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Overview

The Littelfuse KRDM121 is a compact, microcontroller-based time delay relay designed for OEM applications requiring precise timing and space efficiency. Measuring a mere 2 inches (50.8 mm) square, this relay offers a cost-effective solution without compromising reliability or longevity. Its solid-state timing circuit delivers exceptional repeat accuracy of +/- 0.5%, ensuring consistent performance across demanding industrial environments. The KRDM121 features a delay-on-make operation: upon application of input voltage (12VDC for the KRDM121 model), the time delay commences, and the output relay remains de-energized. Only after the set delay period (adjustable from 1 to 100 seconds via an onboard knob) does the output relay energize, staying active until the input voltage is removed. This reset mechanism ensures predictable operation. Encapsulation protects the internal components against shock, vibration, and humidity, further enhancing its suitability for challenging conditions. The isolated, 10A, SPDT output contacts allow for control of both AC and DC loads. Optional accessories like the P1004-95 Versa-Pot and P1023-6 mounting bracket are available for enhanced functionality and installation flexibility. The KRDM121 is an ideal choice for applications where small size, isolation, and reliable, adjustable time delays are critical.
  • Compact 2 in. (50.8 mm) square design for space-constrained OEM applications.
  • Solid-state timing circuit with +/- 0.5% repeat accuracy.
  • Delay-on-make operation with adjustable time delay from 1 to 100 seconds.
  • Encapsulated construction protects against shock, vibration, and humidity.
  • Isolated 10A, SPDT output contacts for AC/DC load control.

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
-20 to 60 F
Operating Temperature, Maximum
60 F
Operating Temperature, Minimum
-20 F
Series
KRDM
Size
2 in. (50.8 mm) square
Special Features
10Y WARR
Standard
CE/UR/CSA
Sub Brand
SSAC
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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.