Eaton residential meter stack 3MM312R12 - UL Listed
Part Number: 3MM312R12
Quick Summary
Eaton residential meter stack enables compact, three-phase group metering for multi-tenant or large-residential installations. Engineers often struggle with space constraints, wiring complexity, and compliance when consolidating meters across multiple units. UL Listed certification ensures safety and reliability, while utility approvals support project acceptability across Idaho Power, Seattle City Light, NV Energy, LADWP, PG&E, SMUD, CenterPoint Energy, Puget Sound Energy, and Tacoma Public Utilities. This architecture enables faster deployment, easier maintenance, and scalable metering for future load growth while minimizing total cost of ownership. For engineers evaluating sourcing, this residential meter stack aligns with group metering product lines and reduces project risk through proven Eaton design and UL compliance.
Product Information
Extended Description
3MM312R12 Eaton: Eaton's Three-Phase Residential Meter Stack Module Group Metering 125A, Aluminum Bus 1200 Ampere, No bypass , Indoor/outdoor, Five-jaws, 3 Sockets, Three-phase in, single-phase out A-B phase Balance, Ring Security, 120/208V
Product Name
Eaton residential meter stack
Catalog Number
3MM312R12
UPC
782114733721
Product Length/Depth
40 in
Product Height
8.5 in
Product Width
15.5 in
Product Weight
56 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
ID : Idaho Power OR : Idaho Power WA : Seattle City Light AK : Anchorage Municipal Light & Power NV : NV Energy 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) TX : CenterPoint Energy (HL&P/Reliant) WA : Puget Sound Energy WA : Tacoma Public Utilities
Interrupt rating
Depends on selected main circuit breaker
Enclosure
Indoor/outdoor
Secondary circuit breaker
BR2_, BRH2_, BRHH2_
Bus Rating
1200 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
Residential and Light Commercial, Metering Products, Volume 1 Tab 4
Eaton Specification Sheet - 3MM312R12
Feature: Three-phase in, single-phase out with group metering. Business Impact: Enables accurate distribution metering for mixed loads while consolidating meters into a single stack, improving space efficiency. Application: Ideal for multi-tenant residential buildings and light commercial facilities where meter management and load balancing are critical. Feature: Five-jaw, three sockets; 125A amperage rating; 120/208V; 1200A bus rating; Aluminum bus. Business Impact: Reduces voltage drop and supports robust capacity in a compact footprint. Application: High-density metering for reliable service in dense developments. Feature: Indoor/outdoor enclosure; No bypass; Ring security; 3-phase inlet, single-phase outlet. Business Impact: Enhances weather resilience, tamper resistance, and safe external installation. Application: Outdoor installations or interior mechanical rooms requiring durable metering solutions. Feature: UL Listed; Utility approvals including Idaho Power, Seattle City Light, NV Energy, LADWP, PG&E, SMUD, CenterPoint Energy, Puget Sound Energy, and Tacoma. Business Impact: Streamlines regulatory acceptance and interconnection, lowering project risk. Application: Utility-driven metering deployments across diverse jurisdictions. Feature: Compatibility with main circuit breakers; Secondary circuit breakers BR2_, BRH2_, BRHH2_; Dimensions and weight: 40 in L, 8.5 in H, 15.5 in W; 56 lb. Business Impact: Simplifies site planning, reduces shipping and handling, and enables flexible system integration. Application: Standardized installation in new builds or retrofit projects. Feature: Warranty: Eaton Selling Policy 25-000; 1 year from install or 18 months from shipment. Business Impact: Clear ownership of post-sale support and predictable maintenance windows. Application: Facility operations teams planning long-term reliability and ROI.
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FAQs
Yes. The 3MM312R12 is designed for three-phase in, single-phase out metering and works with Eaton main circuit breakers chosen for your system’s interrupt rating. The unit supports secondary breakers BR2_, BRH2_, BRHH2_. Ensure the main breaker rating matches the 125A bus and that the installation location is rated indoor/outdoor per enclosure specs.
Key specs include 120/208V voltage, 125A amperage rating, and a 1200A bus rating in an aluminum bus structure. The five-jaw configuration supports five connections, with three sockets for the phase balance A-B. The interrupt rating depends on selected main breaker, and the unit provides three-phase in, single-phase out metering for precise load distribution.
Yes, the Eaton 3MM312R12 is tailored for group metering in multi-tenant residential and mixed-use facilities. Its indoor/outdoor enclosure and rugged aluminum bus provide durable mounting in varied environments, while its 120/208V supply and 125A capacity accommodate typical commercial-residential loads. Use with utility-approved configurations to ensure reliable interconnection.
This meter stack is UL Listed and carries extensive utility approvals across major providers including Idaho Power, Seattle City Light, NV Energy, LADWP, PG&E, SMUD, CenterPoint Energy, Puget Sound Energy, and Tacoma Public Utilities. These approvals streamline interconnection, reduce procurement risk, and help meet local electrical codes for group metering installations.
Eaton provides a warranty under policy 25-000: one year from installation or eighteen months from shipment, whichever occurs first. The modular design and absence of bypass reduce maintenance tasks, while the robust aluminum bus and UL Listing minimize replacement cycles. In practice, customers realize faster deployment, lower field calls, and improved total cost of ownership.