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Mersen A4J70 Class J Fast-Acting Fuse, 70A 600VAC/300VDC Blade Terminal
The Mersen A4J70 Amp-Trap Class J Fast-Acting Fuse delivers professional-grade overcurrent protection with a 70A current rating and dual voltage capability of 600VAC/300VDC. Built with a GMG body insulating material and silver-plated copper blade terminals, this fuse provides 200 kA interrupting capacity and clip mounting for secure, code-compliant installation in commercial and industrial electrical systems.
Key Features
- Ampere Rating: 70A provides precise overcurrent protection for medium-duty electrical circuits and equipment.
- Dual Voltage Rating: 600VAC/300VDC offers versatile protection for both AC and DC electrical systems.
- Fast-Acting Speed Characteristic: Delivers rapid circuit protection to minimize equipment damage during overcurrent conditions.
- 200 kA Interrupting Capacity: Delivers exceptional fault current interruption for enhanced system protection and safety.
- Blade Terminal Connection: Silver-plated copper construction ensures reliable connections with superior conductivity and corrosion resistance.
- Class J Design: Meets professional current-limiting fuse standards with rejection-style mounting.
- Clip Mounting: Enables secure, professional-grade installation.
- Durable Construction: GMG body insulating material supports reliable, long-term performance.
Certifications & Compliance
- RoHS Compliant Construction
Technical Specifications
- Body Insulating Material: GMG
- Rohs Compliant: Yes
Typical Applications
- Commercial Electrical Panels and Distribution Systems
- Industrial Motor Control Centers and Equipment Protection
- HVAC System Overcurrent Protection
- Professional Electrical Service Upgrades
- Multi-Unit Residential Electrical Systems
- Emergency Power and Generator Transfer Applications
Why Mersen?
Mersen engineers the A4J70 Amp-Trap fuse with a precision GMG insulating body and silver-plated copper blade terminals for dependable, corrosion-resistant connections. Combined with 200 kA interrupting capacity and RoHS compliant construction, this Class J fast-acting fuse delivers the reliable, code-compliant overcurrent protection professional electricians expect for demanding commercial and industrial applications.
Manufacturer Resources
Mersen Product Catalog
Product Specs
- Product Type:
- Fast-Acting Fuse
- Product Material:
- GMG
- Voltage Rating:
- 600VAC/300VDC
- Amperage Rating:
- 70A
- Connection Type:
- Blade Terminal
- Series:
- Amp-Trap
- Standards:
- RoHS Compliant
- Configuration:
- Class J
- Department:
- Electrical
- Product Group:
- Circuit Protection
- Product Subgroup:
- Fuses
- Product Length:
- 4.63 in
- Product Weight:
- 0.24 lb
Mersen A4J70 – Frequently Asked Questions
1) Will a Mersen A4J70 fit a Class J fuse block, and will it drop into a Class H or Class R holder?
The A4J70 is a Class J fuse with blade terminals and clip mounting, so it seats in a Class J block or holder of the same amp range. Class J uses rejection-style dimensions, which means it will not fit Class H, K or R holders, and a Class H or R fuse cannot be dropped into a Class J block either. If your existing block is Class J and rated for 70A at 600V, this is the right physical form.
2) Can I use the Mersen A4J70 on a DC circuit?
Yes, within limits. The A4J70 carries a dual rating of 600VAC and 300VDC, so it can protect DC circuits up to 300 volts. Above that, it is out of rating and you need a fuse specified for the higher DC voltage. On AC it can be applied at any system voltage up to 600V.
3) Is a fast-acting Class J fuse like the A4J70 the right choice for a motor circuit?
Fast-acting is the wrong characteristic for motor starting. The A4J70 clears rapidly on overcurrent, which suits feeders, panelboards, transformers and solid-state or electronic loads where inrush is minimal. A motor draws several times full-load current at start, and a fast-acting 70A fuse can open on that inrush. For motor branch circuits a time-delay fuse is the usual pick, such as the Littelfuse CCMR Series Class CC time-delay fuse in the appropriate amp size. Use the A4J70 where the load does not surge, or where you want the fastest current-limiting clearing for component protection.
4) Can a Littelfuse CCMR040 Class CC fuse be used in place of a Mersen A4J70?
No. The Mersen A4J70 is a 70A Class J fast-acting fuse rated 600VAC/300VDC with blade terminals, while the Littelfuse CCMR040 is a Class CC time-delay fuse rated 40A. The two differ in class, so the fuseholder rejection features and physical mounting are not interchangeable, and the CCMR040 is a time-delay element at a lower ampere rating rather than a 70A fast-acting one. Use the CCMR040 only where the drawing calls for a 40A Class CC time-delay fuse, such as motor branch circuits with inrush.
5) I need a fast-acting fuse but the holder is a midget clip, not a Class J block. What should I order?
The Mersen A4J70 is a Class J fuse with clip-mounted blade terminals and will not seat in a midget holder. For a midget-size opening, the Littelfuse BLF series is a midget fast-acting fuse rated 250V in a laminated tube body. Note the voltage difference: the A4J70 carries a 600VAC/300VDC rating, so the BLF is only appropriate on circuits at or below its own 250V rating.
6) What interrupting rating does the Mersen A4J70 have, and is that enough for a high fault-current service?
200 kA interrupting capacity. That covers available fault current on commercial and industrial services well beyond what most panels see, and it is what lets Class J fuses be used in series-rated and current-limiting applications where the available fault current exceeds a breaker's own rating.
7) I need a small inline or midget fuse, not a 70A panel fuse. Is the A4J70 what I want?
No. The A4J70 is a full-size 70A Class J blade-terminal fuse for panel and disconnect clip mounting. For low-amperage electronic, instrument or automotive-style protection, look at glass tube fuses such as the Littelfuse AGA and AGU Series, the Littelfuse BLF Series midget fast-acting 250V fuse, or the Square D PowerLogic energy meter fuse pack (0.5A 600V, set of three) for metering circuits.
8) What part number do I order for the 70 amp Mersen Amp-Trap Class J fuse?
Order Mersen A4J70. The A4J prefix is the Amp-Trap Class J fast-acting family and the trailing number is the ampere rating, so 70 amps here at 600VAC/300VDC.
9) Is a Littelfuse AGU or AGA glass fuse an equivalent to the Mersen A4J70?
No. The Littelfuse AGU and AGA5 are AG-style glass tube fuses used in low-voltage electronics and automotive-type circuits, with the AGA5 rated 5A. The Mersen A4J70 is a 70A Class J fuse rated 600VAC/300VDC with silver-plated copper blade terminals and clip mounting for commercial and industrial panel and motor-control work. They serve different circuits entirely and share no mounting.
10) Our metering cabinet needs the fuses for a PowerLogic meter. Does the A4J70 cover that?
No. Metering potential circuits use a small control fuse, and for a Square D PowerLogic energy meter the matching item is the PowerLogic energy meter fuse pack, a set of three rated 0.5A 600V. The Mersen A4J70 is a 70A Class J fuse for branch and feeder overcurrent protection, not for metering potential taps, though both carry a 600V AC rating.
11) What are the terminals on the Mersen A4J70 made of?
Silver-plated copper blades, with a GMG insulating body. The silver plating matters in the field because it resists oxidation at the clip contact, which is where heat builds when a fuse-to-clip joint degrades.
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Does the Mersen A4J70 come with a warranty?
Absolutely. The Mersen A4J70 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
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