Eaton 3MTB400R Main Terminal Box - NEMA 3R, 400A
Part Number: 3MTB400R
Quick Summary
Eaton main terminal box is designed for high-capacity power distribution in industrial electrical systems. Facility teams often struggle with cramped layouts, mixed wiring schemes, and exposure to the elements that complicate terminations. This unit is UL Listed and housed in a NEMA 3R enclosure, delivering weather resistance and reliable service for overhead or underground installations. With a 400A rating, top or bottom feed, and a 120/208V three-phase configuration, it accommodates scalable power distribution without frequent chassis changes. For contractors and maintenance teams, this translates to faster terminations, reduced splices, and clearer compliance pathways. The Eaton 3MTB400R aligns with industry best practices for aluminum bus conductors and lug-kit landings to improve project timing and long-term reliability.
Product Information
Extended Description
3MTB400R Eaton: Eaton main terminal box, 400A, Aluminum, NEMA 3R, Overhead/underground, Four-wire, Three-phase, 120/208V, (1) #6 AWG-600 kcmil, (2) #1/0 AWG-250 kcmil
Product Name
Eaton main terminal box
Catalog Number
3MTB400R
UPC
786849053086
Product Length/Depth
6.5 in
Product Height
7.5 in
Product Width
13.5 in
Product Weight
54 lb
Warranty
Eaton Selling Policy 25-000, one (1) year from the date of installation of the Product or eighteen (18) months from the date of shipment of the Product, whichever occurs first.
Certifications
UL Listed
Catalog Notes
For compression lug landing kits, order 3MTB1200CLK (includes landings for 3-phases and neutral).
Amperage Rating
400A
Bus material
Aluminum
Feed type
Top/bottom
Phase
Three-phase
Voltage rating
120/208 V
Wire size
(1) #6 AWG-600 kcmil, (2) #1/0 AWG-250 kcmil
Utility approvals
MI : Consumers Energy MI : DTE Energy (Detroit Edison) HI : Hawaiian Electric MT : NorthWestern Energy NE : NorthWestern Energy SD : NorthWestern Energy WY : NorthWestern Energy WI : WE Energies / Wisconsin Public Service (WPS) MD : Baltimore Gas and Electric DC : PEPCO MD : PEPCO
Enclosure
NEMA 3R
Number of wires
4
Residential and Light Commercial, Metering Products, Volume 1 Tab 4
Eaton Specification Sheet - 3MTB400R
Feature: 400A amperage rating with aluminum bus. Business Impact: Delivers robust power capacity while keeping conductor weight low, reducing install time and handling risk. Application: ideal for main distribution in industrial plants and commercial facilities. Feature: NEMA 3R weather-resistant enclosure. Business Impact: Ensures reliable outdoor and indoor performance with superior protection against moisture and dust, lowering maintenance costs. Application: suitable for overhead lines and underground feeders in harsh environments. Feature: Top/bottom feed and four-wire, three-phase design. Business Impact: Flexible wiring options simplify field routing and terminations, cutting project lead times. Application: supports diverse power systems and multi-source distributions. Feature: Large-conductor capacity (1) #6 AWG-600 kcmil, (2) #1/0 AWG-250 kcmil. Business Impact: Enables direct connection of sizable service feeders, reducing splices and tension on cables. Application: suitable for high-current feeders in industrial rigs. Feature: UL Listed certification and compatibility with lug-landing kits. Business Impact: Improves regulatory compliance and procurement confidence, accelerating approval cycles. Application: ideal for utility-compliant installations and retrofit projects. Feature: Compact dimensions and weight (6.5 in depth, 7.5 in height, 13.5 in width, 54 lb). Business Impact: Streamlines space planning and shipping logistics while maintaining robust enclosure strength. Application: fits compact electrical rooms and retrofit scenarios. Catalog notes: When using compression lug landings, reference 3MTB1200CLK for complete phase and neutral landings. Business Impact: Simplifies stocking and reduces field-engineering time. Application: standardizes lug configurations across projects.
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FAQs
The 3MTB400R provides top/bottom feed with a four-wire, three-phase configuration for 120/208V systems, accommodating large service conductors (up to #6 AWG-600 kcmil and #1/0 AWG-250 kcmil). This flexibility simplifies field routing and reduces splicing while enabling robust, scalable power distribution.
Yes. The unit is UL Listed and features a NEMA 3R enclosure, delivering weather resistance suitable for outdoor and exposed installations as well as indoor applications, helping ensure compliance and long-term reliability.
The enclosure dimensions are 6.5 inches depth, 7.5 inches height, and 13.5 inches width, with an approximate weight of 54 pounds, aiding accurate space planning and mounting considerations.
The product is listed with multiple utility approvals, including jurisdictions such as Consumers Energy, DTE Energy, and several Western utility providers, supporting project approvals across varied regions.
Official documentation includes the Eaton Specification Sheet for 3MTB400R and the Residential and Light Commercial Metering Products catalog. You can access these from Eaton’s site to review detailed electrical ratings, installation guidelines, and lug-landing options.