Littelfuse 031801.8H Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 031801.8H is a 1.8 A, 250 V AC/DC fast-blow glass cartridge fuse in the 3AB/3AG package format (1/4" x 1-1/4" axial). This component is classified as obsolete, making equivalent substitute parts necessary for ongoing circuit protection applications. Active alternatives from the same manufacturer series maintain identical electrical and mechanical specifications while offering improved compliance and availability.

Key Parameters

Parameter	Specification
Current Rating	1.8 A
Voltage Rating (AC)	250 V
Response Time	Fast Blow
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (Axial)
Size / Dimension	0.275" Dia x 1.288" L (6.99mm x 32.72mm)
Fuse Type	Cartridge, Glass
Mounting Type	Through Hole
Melting I²t	3.85
DC Cold Resistance	0.082 Ohms

Substitute Part Grouping Explanation

Substitution for the 031801.8H is determined by strict equivalence across the following critical parameters:

Current Rating: 1.8 A (exact match required)
Voltage Rating: 250 V AC (exact match required)
Response Time: Fast Blow (exact match required)
Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (exact match required)
Physical Dimensions: 0.275" Dia x 1.288" L (exact match required)
Melting I²t: 3.85 (exact match required)

All substitute parts listed below meet these criteria. The primary distinction between the main part and substitutes is product status (obsolete vs. active) and compliance certifications.

Parameter Comparison

Parameter	031801.8H	031801.8HXP	031801.8MXP	031801.8VXP
Current Rating (Amps)	1.8 A	1.8 A	1.8 A	1.8 A
Voltage Rating - AC	250 V	250 V	250 V	250 V
Response Time	Fast Blow	Fast Blow	Fast Blow	Fast Blow
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)	3AB, 3AG, 1/4" x 1-1/4" (Axial)
Size / Dimension	0.275" Dia x 1.288" L (6.99mm x 32.72mm)	0.275" Dia x 1.288" L (6.99mm x 32.72mm)	0.275" Dia x 1.288" L (6.99mm x 32.72mm)	0.275" Dia x 1.288" L (6.99mm x 32.72mm)
Melting I²t	3.85	3.85	3.85	3.85
DC Cold Resistance	0.082 Ohms	0.0825 Ohms	0.0825 Ohms	0.0825 Ohms
Breaking Capacity @ Rated Voltage	35A	100A	100A	100A
Product Status	Obsolete	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Operating Temperature	Not specified	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Approval Agency	CSA, UL	CE, CSA, PSE, UL	CE, CSA, PSE, UL	CE, CSA, PSE, UL

Engineering Selection Recommendations

All three substitute parts (031801.8HXP, 031801.8MXP, 031801.8VXP) are direct functional equivalents to the 031801.8H. Selection among these active alternatives should be based on the following factors:

Product Status: The 031801.8H is obsolete. All substitute parts are active and currently manufactured, ensuring long-term availability and supply chain continuity.

Compliance & Certifications: Substitute parts carry expanded approval certifications (CE, CSA, PSE, UL) compared to the main part (CSA, UL). All substitutes are ROHS3 compliant, whereas the main part is non-compliant.

Electrical Performance: Substitute parts feature improved breaking capacity (100A vs. 35A at rated voltage), providing enhanced circuit protection margins. DC cold resistance is marginally higher (0.0825 Ohms vs. 0.082 Ohms), a negligible difference for circuit operation.

Operating Temperature Range: Substitute parts specify -55°C ~ 125°C operating range, whereas the main part does not specify this parameter. This defined range supports thermal design verification.

Packaging: All parts are supplied in bulk packaging for the substitute variants, supporting production and inventory management requirements.

Frequently Asked Questions (FAQ)

Q: Can 031801.8HXP, 031801.8MXP, and 031801.8VXP be used interchangeably with 031801.8H?

A: Yes. All three substitute parts maintain identical current rating (1.8 A), voltage rating (250 V AC), response time (fast blow), package format (3AB/3AG), and physical dimensions (0.275" Dia x 1.288" L). Electrical performance parameters including melting I²t (3.85) are identical.

Q: What is the difference between the three substitute parts?

A: The three substitute parts (031801.8HXP, 031801.8MXP, 031801.8VXP) are parametrically equivalent. Differences are limited to packaging designation and internal manufacturing variants. All three are active products with identical electrical and mechanical specifications.

Q: Why does the 031801.8H have a lower breaking capacity (35A) than the substitutes (100A)?

A: Breaking capacity is a design specification that may differ between product generations or manufacturing revisions. The higher breaking capacity of substitute parts provides improved circuit protection performance without affecting the fuse's primary function at the 1.8 A rated current.

Q: Is the DC cold resistance difference (0.082 Ohms vs. 0.0825 Ohms) significant?

A: No. The difference of 0.0005 Ohms is negligible for circuit operation and does not affect fuse performance or circuit behavior.

Q: Are the substitute parts RoHS compliant?

A: Yes. All substitute parts (031801.8HXP, 031801.8MXP, 031801.8VXP) are ROHS3 compliant. The main part (031801.8H) is RoHS non-compliant.

Q: What certifications do the substitute parts carry?

A: Substitute parts carry CE, CSA, PSE, and UL certifications. The main part carries CSA and UL certifications only.

Q: Can I use these fuses in applications requiring specific operating temperature ranges?

A: Substitute parts specify -55°C ~ 125°C operating range. Verify this range meets your application requirements. The main part does not specify an operating temperature range.

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