Littelfuse 021802.5MXP Glass Cartridge Fuse 2.5A 250VAC 5x20mm Equivalent & Substitute Parts

Part Overview

The Littelfuse 021802.5MXP is a 2.5 A, 250 V AC/DC slow-blow glass cartridge fuse in 5mm x 20mm form factor. This fuse requires a holder for installation and is designed for general-purpose circuit protection applications. The part is active in production with 11,400 units in stock. Equivalent and substitute parts are necessary when the primary part is unavailable, when alternative certifications are required for specific markets, or when different breaking capacity specifications are needed for application-specific requirements.

Key Parameters

Parameter	Value
Current Rating	2.5 A
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Package / Case	5mm x 20mm
Fuse Type	Cartridge, Glass
Mounting Type	Requires Holder
Operating Temperature Range	-55°C ~ 125°C
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the 021802.5MXP is determined by strict equivalence across the following parameters: current rating (2.5 A), voltage rating (250 V AC), response time (slow blow), physical package (5mm x 20mm), and fuse type (cartridge glass). Parts are grouped into three categories:

Direct Manufacturer Equivalents (Littelfuse Series 218): Parts 021802.5HXP and 021802.5TXP share identical electrical characteristics, breaking capacity, melting I²t, and thermal specifications with the main part. These differ only in packaging designation or minor certification variations.

Parametric Equivalents (Littelfuse Series 213 & 219XA, Series 239): Parts 021302.5MXP, 021902.5MXAP, 023902.5MXP, and 023902.5HXP maintain the core electrical parameters (2.5 A, 250 V, slow blow, 5x20mm) but differ in breaking capacity, melting I²t, or approval agency certifications. These are suitable where application requirements permit variation in these secondary parameters.

Cross-Manufacturer Equivalents (Bel Fuse, Eaton, SCHURTER): Parts 5ST 2.5-R, BK/S506-2.5-R, 0034.3780, and 0034.5621.11 maintain the core electrical and physical specifications but originate from different manufacturers. Substitution is valid where cross-manufacturer sourcing is acceptable and certifications align with application requirements.

Parameter Comparison

Part Number	Manufacturer	Series	Current (A)	Voltage (V AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	Inventory (Pcs)
021802.5MXP	Littelfuse Inc.	218	2.5	250	Slow Blow	5x20mm	35	23.25	0.0219	Active	11,400
021802.5HXP	Littelfuse	218	2.5	250	Slow Blow	5x20mm	35	23.25	0.0219	Active	21,272
021802.5TXP	Littelfuse Inc.	218	2.5	250	Slow Blow	5x20mm	35	23.25	0.0219	Active	880
021302.5MXP	Littelfuse Inc.	213	2.5	250	Slow Blow	5x20mm	35	138	0.0305	Active	1,732
021902.5MXAP	Littelfuse	219XA	2.5	250	Slow Blow	5x20mm	150	138	0.0305	Active	1,000
023902.5MXP	Littelfuse	239	2.5	250	Slow Blow	5x20mm	100	79.705	0.0583	Active	3,140
023902.5HXP	Littelfuse	239	2.5	250	Slow Blow	5x20mm	100	79.705	0.0583	Active	2,200
5ST 2.5-R	Bel Fuse Inc.	5ST	2.5	250	Slow Blow	5x20mm	35	20	0.02	Active	6,019
BK/S506-2.5-R	Eaton - Electronics Division	S506	2.5	250	Slow Blow	5x20mm	35	59.4	0.0255	Active	3,012
0034.3780	SCHURTER Inc.	FSL 5x20	2.5	250	Slow Blow	5x20mm	100	9.45	—	Active	1,752
0034.5621.11	SCHURTER Inc.	SMD-FST	2.5	250	Slow Blow	5x20mm	35	21.9	—	Active	1,013

Engineering Selection Recommendations

Tier 1 - Direct Substitutes (Preferred): 021802.5HXP and 021802.5TXP are direct equivalents within the Littelfuse 218 series. Both maintain identical electrical performance, breaking capacity (35 A), and melting I²t (23.25). Selection between these and the main part should be based on inventory availability and packaging designation requirements. All three carry comprehensive certifications (CCC, CE, CSA, K-MARK, PSE, SEMKO, UL, VDE).

Tier 2 - Littelfuse Series Alternatives: 021302.5MXP (Series 213), 021902.5MXAP (Series 219XA), 023902.5MXP, and 023902.5HXP (Series 239) are parametric equivalents suitable when application requirements permit higher breaking capacity or different melting I²t characteristics. The Series 219XA part (021902.5MXAP) offers 150 A breaking capacity, appropriate for high-fault-current environments. Series 239 parts provide 100 A breaking capacity. Certification coverage varies; verify alignment with target market requirements.

Tier 3 - Cross-Manufacturer Alternatives: Bel Fuse 5ST 2.5-R, Eaton BK/S506-2.5-R, and SCHURTER 0034.3780 and 0034.5621.11 maintain core electrical specifications and 5x20mm form factor. These are suitable where multi-source qualification is established and certifications meet application standards. SCHURTER 0034.3780 offers 100 A breaking capacity; SCHURTER 0034.5621.11 matches 35 A breaking capacity of the main part.

Certification Considerations: All parts are ROHS3 compliant and REACH unaffected. Littelfuse parts carry the broadest certification coverage. SCHURTER 0034.3780 is limited to cULus certification; verify adequacy for target applications. Eaton BK/S506-2.5-R includes PSE/JET certification for Japanese market applications.

Frequently Asked Questions (FAQ)

Q: Can I substitute 021802.5HXP for 021802.5MXP without any circuit modifications?

A: Yes. Both parts are Littelfuse Series 218 fuses with identical current rating (2.5 A), voltage rating (250 V), response time (slow blow), breaking capacity (35 A), melting I²t (23.25), and physical dimensions (5x20mm). No circuit modifications are required.

Q: What is the difference between the Littelfuse Series 218, 213, and 239 fuses?

A: All three series maintain the same current rating (2.5 A), voltage (250 V), response time (slow blow), and package (5x20mm). The primary differences are breaking capacity and melting I²t: Series 218 has 35 A breaking capacity and 23.25 melting I²t; Series 213 has 35 A breaking capacity but 138 melting I²t; Series 239 has 100 A breaking capacity and 79.705 melting I²t. Selection depends on application fault-current requirements.

Q: Can I use a cross-manufacturer fuse like the Bel Fuse 5ST 2.5-R or Eaton BK/S506-2.5-R as a direct replacement?

A: Cross-manufacturer parts maintain the same electrical ratings and physical package, making them mechanically and electrically compatible. However, verify that the target application and end-market certifications accept the alternative manufacturer. Bel Fuse and Eaton parts carry different certification agencies than Littelfuse; confirm alignment with your compliance requirements.

Q: Why do some substitute parts have different melting I²t values?

A: Melting I²t is a thermal characteristic that affects fuse response time under specific fault conditions. Parts with higher melting I²t (such as Series 213 at 138 or Series 239 at 79.705 versus Series 218 at 23.25) respond more slowly to thermal stress. Selection should match application requirements for nuisance-trip prevention and fault-clearing speed.

Q: Is the SCHURTER 0034.3780 suitable for all applications where the 021802.5MXP is used?

A: The SCHURTER 0034.3780 maintains the same current, voltage, response time, and package specifications. However, it is certified only by cULus, whereas the 021802.5MXP carries broader certifications (CCC, CE, CSA, K-MARK, PSE, SEMKO, UL, VDE). Substitution is valid only if cULus certification meets your application and market requirements.

Q: What does "Requires Holder" mean for these fuses?

A: All listed fuses are cartridge-type glass fuses that require a separate fuse holder for installation. The fuse itself is not self-contained; it must be inserted into a compatible 5x20mm fuse holder. Ensure your circuit design includes an appropriate holder rated for 250 V AC and 2.5 A minimum.

Q: Can I use the 021902.5MXAP (150 A breaking capacity) in place of the 021802.5MXP (35 A breaking capacity)?

A: Yes, from an electrical and mechanical standpoint. The 021902.5MXAP is rated for higher fault currents (150 A versus 35 A) and is therefore suitable for applications with higher available short-circuit current. This substitution is conservative and does not compromise circuit protection; however, verify that your application environment justifies the higher breaking capacity specification.

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