Eaton 400A Fusible Switch, Alu...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$2,026.61
Eaton 400A Fusible Switch, Aluminum Bus, NEMA 3R, Class T

Eaton 400A Fusible Switch, Aluminum Bus, NEMA 3R, Class T

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Model: 1MFS400RB

In Stock (leaves warehouse same day if ordered before 3pm ET)

$2,026.61
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Eaton 400A Fusible Switch, Aluminum Bus, NEMA 3R, Class T

Eaton's 400A Fusible Switch is a heavy-duty main disconnect built for demanding single-phase electrical service applications. Featuring an aluminum bus, a NEMA 3R rated enclosure suited to outdoor and wet-location installation, and Class T fuse clips, this switch delivers a 100 kAIC interrupt rating for reliable overcurrent protection. Rated 120/240V for three-wire, single-phase service, it accepts (1) #750 kcmil conductor per phase, making it well suited for main service entrance and multi-family metering applications.

Key Features

  • Amperage Rating: 400A fusible switch for high-capacity service entrance applications.
  • Durable Construction: Aluminum bus construction for dependable current-carrying performance.
  • Fuse Clip Type: Class T fuse clips deliver compact, high-performance overcurrent protection.
  • Interrupt Rating: 100 kAIC rating supports safe operation under high fault-current conditions.
  • Wire Configuration: Three-wire, single-phase, 120/240V service; line rated for (1) #750 kcmil.
  • Enclosure: NEMA 3R rated enclosure for outdoor and wet-location installations.
  • Barrier Kit Compatible: Barrier kits available for 400A-800A fusible switches — Bottom feed 3MFSBBK, Top feed 3MFSTB.
  • Fuse Clip Upgrade Path: Class H fuse clips available via catalog number WCG3HK400 (order (1) per phase); Class R requires WCG3HK400 plus DS56FK, converting first to Class H.

Certifications & Compliance

  • UL Listed
  • NEMA 3R Rated Enclosure

Technical Specifications

  • Number of wires: 3
  • Department: Electrical
  • Voltage rating: 120/240 V
  • Amperage Rating: 400A
  • Phase: Single-phase
  • Bus material: Aluminum
  • Fuse clip type: Class T
  • Line: (1) #750 kcmil
  • Interrupt rating: 100 kAIC
  • Enclosure: NEMA 3R

Typical Applications

  • Commercial and Industrial Electrical Service Entrances
  • Multi-Family and Multiple Metering Installations
  • Panelboard and Load Center Main Disconnect Switching
  • Outdoor and Wet-Location Installations
  • Renovation and New Construction Electrical Upgrades

Why Eaton?

Eaton builds this 400A fusible switch with an aluminum bus, Class T fuse clips, and a 100 kAIC interrupt rating to deliver dependable, code-compliant performance for critical service entrance applications. The UL Listed, NEMA 3R rated construction gives electrical professionals confidence in both indoor and outdoor installations, backed by Eaton's established reputation for main disconnect and service equipment reliability.

Manufacturer Resources

Product Specs

Voltage Rating:
120/240V
Amperage Rating:
400A
Phase:
Single-phase
Bus material:
Aluminum
Certifications:
UL Listed
Fuse clip type:
Class T
Line:
(1) #750 kcmil
Interrupt rating:
100 kAIC
Number of wires:
3
Configuration:
NEMA 3R Enclosure
Product Type:
Safety Switch
Department:
Electrical
Product Material:
Aluminum
Listing:
UL Listed
Product Group:
Power Distribution
Product Subgroup:
Safety Switches & Disconnects

Eaton 1MFS400RB – Frequently Asked Questions

1) What is the difference between the Eaton 1MFS400RB and 1MFS400RT fusible switch?
The two versions of Eaton's 400A fusible switch differ by service feed direction. Order 1MFS400RB for an underground service lateral and 1MFS400RT for an overhead service drop. Everything else is the same: 400A, 120/240V single-phase three-wire, Class T fuse clips, aluminum bus, 100 kAIC, NEMA 3R. Getting the feed direction wrong means the conductors enter from the wrong end of the enclosure, so confirm how the utility is bringing service to the building before you order.
2) Can the Eaton 400A fusible switch be mounted outdoors on the side of a building?
Outdoor mounting is what the NEMA 3R enclosure is for. It handles rain and wet locations, which covers a typical exterior service entrance wall or a meter bank on a multi-family building. NEMA 3R is a rainproof rating, not a washdown or dust-tight one, so it is not the enclosure for a hosed-down or heavily corrosive interior. It is UL Listed.
3) What size conductor will the Eaton 400A fusible switch lugs accept?
The line side is rated for (1) #750 kcmil per phase. That is a single large conductor per phase rather than parallel runs, so if your design calls for paralleled 4/0 or 250 kcmil sets, the terminations will not land here as-is. Size your service conductors for the 400A rating and plan a single 750 kcmil per phase.
4) Will the Eaton 400A fusible switch work on a 208V or 480V three-phase service?
No. This is a 120/240V, single-phase, three-wire device. It is built for a residential-style or small commercial single-phase service entrance. For 208Y/120 or 480Y/277 three-phase service you need a three-phase fusible switch, not this one. The three wires here are two ungrounded conductors plus a neutral.
5) What fuses does the Eaton 400A fusible switch take, and can I use Class R or Class H fuses instead?
It ships with Class T fuse clips. Class T fuses are physically shorter and smaller than Class H or Class R of the same amperage, so they are not interchangeable in the same clips. Eaton publishes an upgrade path: catalog number WCG3HK400 converts the switch to Class H clips, ordered one per phase. For Class R you need WCG3HK400 plus DS56FK, converting to Class H first and then to Class R. Budget for those kits at the time of order if your spec or your existing fuse stock is Class R.
6) Is 100 kAIC enough for a service entrance with a large utility transformer?
100 kAIC is the interrupt rating, and it is at the top end of what is offered for single-phase service equipment. It covers service points where the available fault current is high, which is typical of a close-coupled or large utility transformer feeding a multi-family meter bank. The engineer's fault current study governs the final call, but 100 kAIC leaves substantial headroom over the 22 kAIC and 65 kAIC ratings common on lighter service equipment.
7) Do I need a barrier kit with the Eaton 400A fusible switch for a multiple-metering installation?
Barrier kits are available for 400A through 800A fusible switches and are ordered by feed direction: 3MFSBBK for bottom feed, 3MFSTB for top feed. They are the accessory to add when a metering installation requires the line side to be barriered off from tenant-accessible or utility-sealed sections. Match the kit to how the service enters, the same way you match the underground or overhead version of the switch itself.
8) Should I use a fusible switch or a main breaker disconnect for a 400A service entrance?
A fusible switch like this Eaton 400A unit separates the switching from the overcurrent device: the blade switch opens the circuit, and replaceable Class T fuses clear the fault. That buys a very high interrupt rating (100 kAIC here) in a compact enclosure, and it is why fusible gear is common where available fault current is high. The trade is that after a fault you replace fuses rather than reset a handle, and you have to keep spare 400A Class T fuses on hand. A main breaker disconnect resets, which property managers usually prefer on openings they service themselves.
9) Can the Eaton 400A fusible switch be used as the service disconnect ahead of a panelboard?
That is the intended use. It functions as a main disconnect for a 120/240V single-phase, three-wire service, sitting ahead of a panelboard or load center, and is UL Listed for the role. Typical placements are commercial and industrial service entrances, multi-family metering, and service upgrades on renovation work. Take the 400A rating as the ceiling on the downstream panel.
10) Is an aluminum bus a problem in a 400A service disconnect?
The bus in this Eaton 400A switch is aluminum, which is standard construction for service equipment at this rating and is UL Listed as built. The practical consequence is at the terminations: aluminum connections want the manufacturer's torque values applied and re-checked, and any aluminum service conductor landing in the lugs should get an oxide-inhibiting compound. If a project spec explicitly calls for copper bus, this switch will not satisfy that line.
How fast can I get the Eaton 1MFS400RB delivered?
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Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Eaton 1MFS400RB come with a warranty?
Absolutely. The Eaton 1MFS400RB is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Eaton 1MFS400RB?
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