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Mersen A4BY Class L Time-Delay Fuse, Blade Terminal, 600VAC/300VDC
Model: MER-A4BY
Mersen A4BY Class L Time-Delay Fuse, Blade Terminal, 600VAC/300VDCThe Mersen A4BY Class L Time-Delay Fuse delivers reliable circuit protection for high-amperage applications, rated 3000A with dual...
Mersen
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$1,881.67
Mersen A4BY Class L Time-Delay Blade Fuse, 600VAC
The Mersen Amp-Trap Series A4BY is a Class L, time-delay fuse family built for protecting service entrance equipment, feeder circuits, and circuit breakers, rated 600VAC / 300VDC with a blade terminal connection for bolted mounting. This page covers the A4BY line across its Motor FLA ratings, available from 601A through 3500A, so contractors and engineers can select the current rating that matches the application while every unit in the family shares the same voltage, interrupting, and construction specifications. As a 100% rated device, the A4BY may be applied at continuous currents up to its full ampere rating, and its 4-second minimum time delay at 500% rating lets it pass normal current surges while coordinating cleanly with ground fault relays. Silver-plated copper blade terminals and a GMG body/insulating material support a 200 kA AC interrupting rating at 50/60 Hz for demanding industrial and commercial power distribution applications.
Key Features
- Motor FLA Rating Range: Available in 601A, 700A, 900A, 1200A, 1400A, 1500A, 1600A, 1800A, 2000A, 2500A, and 3500A ratings to match specific feeder and service entrance loads.
- Fuse Class: Class L, time-delay characteristic for coordinated overcurrent protection.
- Connection/Terminal Type: Blade terminal with bolted mounting for secure, low-resistance connections.
- Terminal Material: Silver-plated copper for reliable conductivity and corrosion resistance.
- Voltage Rating: 600VAC / 300VDC for a broad range of service entrance and feeder applications.
- Interrupting Rating: 200 kA AC maximum breaking capacity for high fault-current environments.
- Frequency: Rated for 50/60 Hz power systems.
- 100% Rated Device: May be applied at continuous currents up to its full ampere rating.
- Time Delay: 4-second minimum delay at 500% rating allows normal current surges to pass and coordinates with ground fault relays.
- Body/Insulating Material: GMG construction, shared across all Motor FLA ratings in the A4BY family.
Certifications and Compliance
- RoHS Compliant
Technical Specifications
- Motor FLA Rating Options: 601A, 700A, 900A, 1200A, 1400A, 1500A, 1600A, 1800A, 2000A, 2500A, 3500A
- ROHS Compliant: Yes
- Body/Insulating Material: GMG
- Connection/Terminal Type: Blade
- Mounting: Bolted
- Connection/Terminal Material: Silver-Plated Copper
- AC Max I.R./Breaking Capacity: 200 kA
- Frequency: 50/60 Hz
- Speed/Characteristic: Time Delay
- Rated Voltage AC UL: 600 V
- Fuse Class: Class L
- Packaging: 1 EA
Typical Applications
- Service Entrance Equipment Protection
- Feeder Circuit Overcurrent Protection
- Circuit Breaker Coordination
- Ground Fault Relay Coordination
- Commercial and Industrial Power Distribution
Why Mersen?
Mersen's Amp-Trap Series A4BY combines silver-plated copper blade terminals, a GMG body, and a 200 kA interrupting rating to deliver dependable, code-compliant overcurrent protection for Class L applications across its full 601A-3500A Motor FLA range. Its 100% rated, time-delay design gives electrical contractors and engineers a trusted solution for coordinating service entrance and feeder protection on demanding 600VAC / 300VDC systems, no matter which ampere rating the job requires.
Manufacturer Resources
Mersen Product Catalog
Product Specs
- Connection Terminal Type:
- Blade
- Mounting Method:
- Bolted
- Connection/Terminal Material:
- Silver-Plated Copper
- AC Max I.R./Breaking Capacity: I1:
- 200 kA
- ROHS Compliant:
- Yes
- Frequency (Hz):
- 50/60 Hz
- Speed/Characteristic:
- Time Delay
- Rated voltage AC UL:
- 600 V
- Fuse Class:
- Class L
- Body/Insulating Material:
- GMG
- list_batch:
- MERSEN-20260825
- Department:
- Electrical
- Product Group:
- Circuit Protection
- Product Type:
- Blade Fuse
- Product Material:
- GMG
- Connection Type:
- Blade
- Voltage Rating:
- 600V
- Amperage Rating:
- 601A - 3500A
- Product Finish:
- Silver-Plated Copper
- Series:
- A4BY
- Product Subgroup:
- Fuses
Mersen A4BQ1200 – Frequently Asked Questions
1) What amp ratings does the Mersen A4BY Class L fuse come in?
The A4BY Amp-Trap family covers 601A through 3500A, with ratings of 601, 700, 900, 1200, 1400, 1500, 1600, 1800, 2000, 2500 and 3500 amps. That range is sized for service entrance and feeder work rather than branch circuits, where Class L starts at 601A by definition. Ordering codes run A4BY601, A4BY900 and A4BY1500 alongside A4BQ-prefixed numbers such as A4BQ700, A4BQ1200 and A4BQ3500.
2) Will a Class L blade fuse bolt into my existing fuse holder, or do I need clips?
These are bolt-in, not clip-in. The A4BY uses blade terminals with bolted mounting, so the gear needs Class L bolt pads on the line and load side. A clip-style holder built for ferrule or knife-blade cartridge fuses will not take it. The blades are silver-plated copper, which keeps contact resistance low at the bolted joint.
3) Is the Mersen A4BY rated for a 480V or 600V three-phase service?
Yes on both. The A4BY carries a 600VAC UL rating, so it can be applied on 208V, 480V or 600V AC systems at 50/60 Hz. The description also gives a 300VDC rating for DC applications. Never apply it above 600VAC.
4) Is 200kA interrupting enough for my service entrance available fault current?
200 kA is the maximum AC breaking capacity on the A4BY, which is the top of the range for Class L and covers essentially any utility service short-circuit current you will see on a commercial or industrial entrance. Compare it against the available fault current on your utility letter or short-circuit study; if that number is at or under 200 kA, the fuse is adequately rated.
5) Will this fuse nuisance-open on motor inrush or transformer magnetizing current?
It shouldn't. The A4BY is a time-delay characteristic with a 4-second minimum delay at 500% of rating, so starting inrush and transformer magnetizing surges ride through. That same delay is what lets it coordinate with downstream breakers and ground fault relays instead of racing them. If you need fast clearing for semiconductor or non-inductive loads, a time-delay Class L is the wrong choice.
6) Can a Littelfuse CCMR Class CC time-delay fuse be used in place of a Mersen A4BY?
No. Both are time-delay fuses, but they are different UL fuse classes and different physical bodies. The Mersen A4BY is a Class L fuse with blade terminals that bolt into the fuse holder, rated 600VAC, covering 601A through 3500A. The Littelfuse CCMR040 is a Class CC fuse rated 40A. Class CC is a small ferrule-style branch-circuit fuse used in control circuits and small motor starters; it will not mount in a Class L bolted-blade mount and comes nowhere near the ampacity of a service entrance or feeder application. Use a Class L fuse where the equipment is prepped for one.
7) Should I use a Class L fuse or a Class CC fuse for my job?
They sit at opposite ends of the system. Class L, like the Mersen A4BY, starts at 601A and goes to 3500A, bolted into service entrance and main feeder gear. Class CC is a small midget-body fuse for control circuits, motor branch protection and small loads. For a 40A motor branch you would use something like the Littelfuse CCMR040 Class CC time-delay fuse, not a Class L.
8) I need to replace a 1500A main fuse. Which part number do I order?
For a 1500A rating the part number is A4BY1500. Neighbouring sizes are A4BQ1400 and A4BQ1600, so confirm the rating stamped on the fuse you are pulling before you order; Class L amp ratings are not interchangeable and the holder is sized to the fuse.
9) I need a 600V fuse and found the Square D PowerLogic meter fuse pack. Is that interchangeable with the Mersen A4BY?
No, despite the shared 600V class. The Square D PowerLogic energy meter fuse pack is a set of three 0.5A 600V fuses intended to protect metering voltage inputs, a sensing-circuit duty. The Mersen A4BY is a Class L power fuse from 601A to 3500A with silver-plated copper blade terminals and a 200 kA AC interrupting rating, built to clear faults on service entrance equipment and feeders. The two protect opposite ends of the system and share no form factor.
10) Is a glass tube fuse like the Littelfuse AGU or AGA an option for feeder protection instead of the Mersen A4BY?
No. The Littelfuse AGU and AGA5 are AG-style glass tube fuses used in low-voltage automotive and appliance circuits. The Mersen A4BY is a Class L bolted blade fuse with a GMG body, rated 600VAC at 50/60 Hz with a 200 kA AC interrupting rating, and it is a 100 percent rated device with a 4-second minimum delay at 500 percent of rating so it coordinates with ground fault relays. Feeder and service entrance protection requires the Class L device; a glass tube fuse has neither the interrupting capacity nor the mounting.
11) What is the difference between a fast-acting midget fuse like the Littelfuse BLF and the time-delay Mersen A4BY?
They differ in both clearing speed and scale. The Littelfuse BLF is a midget fast-acting fuse rated 250V in a laminated tube body, which opens quickly on overcurrent and is suited to circuits with no inrush to ride through. The Mersen A4BY has a time-delay characteristic with a 4-second minimum delay at 500 percent of rating, which lets normal motor and transformer inrush pass, and it is rated 600VAC with blade terminals for bolted mounting in ratings from 601A up. Choose the time-delay Class L device where surge current is expected on a feeder or service entrance.
12) What is the Mersen A4BY fuse body made of, and is it RoHS compliant?
The body and insulating material is GMG, used across every amp rating in the A4BY family, with silver-plated copper blades. The fuse is RoHS compliant, which is usually what institutional and government specs are asking about on submittals.
13) How are Mersen A4BY fuses packaged, individually or in sets of three?
They ship one each. Packaging on the A4BY is 1 EA, so for a three-phase service you order three fuses of the matching amp rating. That differs from small metering fuses such as the Square D PowerLogic fuse pack, which is sold as a set of three.
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Absolutely. The Mersen A4BQ1200 is backed by a manufacturer’s warranty.
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