Eaton 3MM312R Residential Meter Stack - UL Listed

Part Number: 3MM312R
Manufacturer
Eaton
Part number
3MM312R

Quick Summary

Eaton 3MM312R residential meter stack is a three-phase in, single-phase out module designed for group metering in multi-tenant facilities. In practice, installers face space constraints and wiring complexity when stacking meters, and balance among feeders can be difficult without a compact, properly rated solution. UL Listed certification underpins safety and regulatory compliance, while the indoor/outdoor enclosure and an 800 A aluminum bus support durable, versatile deployments. By integrating group metering with reliable performance, it simplifies compliance reporting, reduces enclosure clutter, and enables scalable metering strategies for growing electrical systems. This approach aligns with broader metering product families and supports faster procurement and installation workflows.

Product Information

Extended Description

3MM312R Eaton: Eaton's Three-Phase Residential Meter Stack Module, Group Metering Type, 125A, Aluminum Bus 800 Ampere, No bypass, Indoor/outdoor, Five-jaws, 3 Sockets, Three-phase in, single-phase out, Ring Security, 120/208V
Product Name
Eaton residential meter stack
Catalog Number
3MM312R
UPC
786849051976
Product Length/Depth
40 in
Product Height
8 in
Product Width
15 in
Product Weight
53 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
Type
Group Metering
Utility approvals
MD : First Energy (Potomac Edison) AL : Alabama Power DC : Atlantic City Electric / Delmarva (Connectiv) DE : Atlantic City Electric / Delmarva (Connectiv) MD : Atlantic City Electric / Delmarva (Connectiv) NJ : Atlantic City Electric / Delmarva (Connectiv) TX : CenterPoint Energy (HL&P/Reliant) NC : Dominion VA : Dominion MI : DTE Energy (Detroit Edison) NM : El Paso Electric TX : El Paso Electric MO : Empire District Electric OK : Empire District Electric AR : Entergy LA : Entergy MS : Entergy TX : Entergy CA : City of Los Angeles - DWP (LADWP) AZ : Southern California Edison CA : Southern California Edison CA : Pacific Gas and Electric (PG&E) CA : Sacramento Municipal Utility District (SMUD) TN : Nashville Electric Service CA : PacifiCorp/Pacific Power/Rocky Mountain Power ID : PacifiCorp/Pacific Power/Rocky Mountain Power OR : PacifiCorp/Pacific Power/Rocky Mountain Power UT : PacifiCorp/Pacific Power/Rocky Mountain Power WA : PacifiCorp/Pacific Power/Rocky Mountain Power WY : PacifiCorp/Pacific Power/Rocky Mountain Power HI : Hawaiian Electric MT : NorthWestern Energy NE : NorthWestern Energy SD : NorthWestern Energy WY : NorthWestern Energy MD : Baltimore Gas and Electric DC : PEPCO MD : PEPCO AZ : Tucson Electric Power/ UniSource AZ : Sulphur Springs Valley Electric Coop IN : Indianapolis Power and Light (IP&L)
Interrupt rating
Depends on selected main circuit breaker
Enclosure
Indoor/outdoor
Secondary circuit breaker
BR2_, BRH2_, BRHH2_
Bus Rating
800 A
Phase
Three-phase in, single-phase out
Voltage rating
120/208V
Amperage Rating
125A
Bus material
Aluminum
Bypass
None
Number of jaws
Five-jaw
Number of sockets
3
Phase balance
A-B
Security
Ring
Feature: Three-phase in, single-phase out design enables efficient group metering for multi-tenant facilities. Business impact: Delivers clear load visibility while reducing wiring complexity and installation time. Application: Ideal for residential and light-commercial meter stacks where scalable metering is required. Feature: 125 A input with an 800 A aluminum bus rating supports high-load feeders with lightweight, corrosion-resistant conductors. Business impact: Improves service reliability and reduces copper cost and enclosure weight. Application: Suitable for large multi-dwelling complexes and small commercial buildings needing robust bus performance. Feature: Five-jaw connections and three sockets with no bypass provide secure, flexible connections and safer fault isolation. Business impact: Minimizes mis-wiring risk and accelerates fault containment. Application: Complements BR2_, BRH2_, BRHH2_ secondary breakers for streamlined installations. Feature: Indoor/outdoor enclosure versatility enables placement in a variety of environments. Business impact: Reduces the need for additional enclosures and supports outdoor metering without compromise. Application: Ideal for corridor cabinets, exterior meter canopies, or utility-friendly spaces. Feature: UL Listed certification and broad utility approvals reinforce safety and regulatory compliance. Business impact: Facilitates procurement and reduces commissioning risk across utilities. Application: Suitable for regulated installations in residential and light-commercial settings.

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FAQs

Prepare for indoor/outdoor deployment and ensure proper enclosure clearance for a five-jaw, three-socket assembly. Confirm alignment with feeder layouts for three-phase in, single-phase out configurations and verify compatibility with BR2_, BRH2_, BRHH2_ secondary breakers to simplify wiring and enhance safety during commissioning.
It features a 125 A input and an 800 A aluminum bus, supporting high-load feeders while keeping enclosure weight manageable. Interrupt rating depends on the selected main circuit breaker, and it is designed to work with BR2_, BRH2_, BRHH2_ secondary breakers for flexible, safe fault isolation.
Yes. The unit is designed for group metering with three-phase in, single-phase out, and 120/208 V operation, making it ideal for multi-tenant or distributed metering scenarios. Its UL Listed status further supports regulatory compliance and consistent metering performance across sites.
The product is UL Listed, a key safety certification for electrical equipment. It also includes extensive utility approvals in its specifications, supporting installation across a broad range of utility territories and reducing the time required for site acceptance testing.
Warranty follows Eaton policy 25-000, offering one year from installation or eighteen months from shipment, whichever occurs first. The design minimizes external enclosures, and its rugged aluminum bus reduces long-term maintenance costs. Pairing with Eaton data sheets and compatible secondary breakers helps accelerate deployment and improve lifecycle value.