ANSI/IEEE C57.12.25 · UL Listed / cUL · DOE Compliant · 167 kVA & Below · 34.5 kV Class
Built for underground residential and commercial single-phase distribution across the Americas — 5 kVA to 167 kVA, 4.16 kV through 34.5 kV class, dead-front tamper-resistant construction, loop or radial feed, UL/cUL and CSA certification options.
Single-phase pad-mounted distribution transformers in the Americas are specified against ANSI/IEEE C57.12.25, not the three-phase C57.12.34. C57.12.25 defines the electrical, dimensional, and mechanical characteristics for compartmental-type, self-cooled, single-phase distribution transformers with separable insulated high-voltage connectors — rated 167 kVA and smaller, high voltage 34,500 GrdY/19,920 V and below, low voltage 240/120 V. It assumes 60 Hz, mineral-oil-immersed construction as the baseline reference.
Our single-phase platform is engineered directly to this standard, with UL Listing and cUL available for U.S. and Canadian utility acceptance, and CSA for Canadian electrical code compliance. For Americas procurement, the non-negotiable stack is C57.12.25 + UL Listing + DOE efficiency — without these three, a single-phase pad-mount cannot enter most utility approved-vendor lists.
| Standard / Mark | Scope |
|---|---|
| IEEE/ANSI C57.12.25 | Single-phase pad-mounted compartmental-type design, ≤167 kVA, ≤34.5 kV class |
| IEEE/ANSI C57.12.00 | General requirements for liquid-immersed distribution transformers |
| UL Listed / cUL | Safety certification for U.S. and Canadian markets |
| CAN/CSA | Canadian electrical code compliance option |
| DOE 2016 / DOE 2027-ready | Energy efficiency compliance for distribution transformers |
| NEMA TR-1 | Sound level and loss tolerance |
| IEEE C57.12.28 / C57.12.29 | Enclosure integrity and coating performance |
| ISO 9001 | Manufacturing quality system |
| SGS | Third-party inspection available |
Single-phase pad-mounts sit on residential lots, commercial frontages, and public rights-of-way. Dead-front construction is the baseline safety requirement in North American utility specifications, and is increasingly mandated in Latin American urban distribution. Our units ship with HV bushing wells for dead-front elbow connectors (200 A interface), lockable stainless-steel hinged doors, tamper strips, and fully sealed tank construction — no exposed live parts at grade level. The enclosure meets IEEE C57.12.28 integrity requirements, with coating performance tested to C57.12.28 / C57.12.29 for corrosion resistance.
North American underground residential distribution (URD) is predominantly loop-feed for back-feed capability and outage isolation. Latin American residential and commercial projects frequently use radial feed for first-cost efficiency. Our single-phase platform supports both loop and radial feed on the same tank and enclosure design, with 2-position load-break switch or sectionalizing switch options. Specify feed type at order — no separate product line, no requalification.
Primary voltage options cover the ratings actually used across the Americas:
34.5–19.92 kV（34,500 GrdY / 19,920 V）
24.94–14.4 kV
13.8–7.957 kV
13.2–7.62 kV
12.47–7.2 kV（12,470 GrdY / 7,200 V）
4.16 kV
Secondary voltages include 120/240 V, 240/480 V, 277 V, 347 V, and 600 V, with custom combinations available. This range directly matches single-phase distribution voltages used by CFE (Mexico), ICE/CNFL (Costa Rica), ETESA (Panama), ENEE (Honduras), and Caribbean utilities at 12.47 kV and 13.8 kV — the two most common single-phase pad-mount ratings in the region.
C57.12.25 defines the single-phase pad-mount scope as 167 kVA and smaller. Standard ratings include 5, 10, 15, 25, 37.5, 50, 75, 100, and 167 kVA; 250 kVA is available as an extended-range option where project load requires it. For residential subdivisions, commercial lighting, small industrial single-phase loads, and rural electrification, this capacity range covers the vast majority of pad-mount single-phase demand.
DOE efficiency is a purchasing gate for U.S. utilities and a benchmarking requirement for Latin American buyers comparing total cost of ownership. Our single-phase platform is designed to DOE 2016 efficiency levels, with DOE 2027-ready configurations available on request. Lower no-load and load losses translate directly into reduced lifecycle operating cost — the metric utility procurement teams use to compare pad-mount bids beyond first cost.
The single-phase protection architecture follows ANSI utility practice: bayonet expulsion fuse for overload and fault clearing, isolation link, pressure relief device, oil level gauge, drain and sample valve, and no-load tap changer as standard accessories. Optional current-limiting backup fuse is available for high-fault-current locations. This is the protection set that utility standards reference for single-phase compartmental pad-mounts.
Winding material and insulating fluid are specification variables in Americas procurement. Copper windings for high-load or high-harmonic duty; aluminum windings for standard residential distribution at lower weight and cost. Fluid options include Type II mineral oil and natural ester (FR3-type) for fire-sensitive or environmentally regulated sites. Both fluid types are available with the same UL/ANSI compliance package.
| Parameter | Range / Options |
|---|---|
| Phase | Single-phase |
| Primary Voltage | 4.16 kV, 12.47–7.2 kV, 13.2–7.62 kV, 13.8–7.957 kV, 24.94–14.4 kV, 34.5–19.92 kV |
| Secondary Voltage | 120/240 V, 240/480 V, 277 V, 347 V, 600 V, custom |
| Capacity | 5 kVA – 167 kVA（standard per C57.12.25）；250 kVA available as extended option |
| Frequency | 60 Hz standard; 50 Hz available |
| Feed Type | Loop feed / Radial feed |
| Front Design | Dead-front（standard）；live-front available on request |
| HV Tap Range | ±2 × 2.5%（standard） |
| Connection | Delta / Wye |
| Cooling | ONAN / KNAN |
| Temperature Rise | 55°C / 65°C |
| BIL | 30 kV – 150 kV primary（by voltage class） |
| Winding Material | Copper / Aluminum |
| Insulating Fluid | Type II mineral oil / Natural ester（FR3-type） |
| HV Bushing | Dead-front bushing wells, 200 A interface |
| Fusing | Bayonet expulsion fuse; isolation link; optional current-limiting backup fuse |
| Enclosure | Tamper-resistant, lockable; IEEE C57.12.28 integrity; C57.12.28/29 coating |
| Standards | IEEE/ANSI C57.12.25, C57.12.00, CAN/CSA, DOE, NEMA |
| Certification | UL Listed, cUL, CSA, SGS |
Specification table reflects the platform’s standard range; every unit is built to order with project-specific voltage, BIL, fusing, and enclosure requirements.
Single-phase pad-mounted transformers serve the last-mile single-phase distribution layer — residential subdivisions, commercial frontages, rural electrification, and small industrial single-phase loads. Specific deployment scenarios:
Residential underground distribution (URD) — loop-feed subdivisions and single-family home service
Commercial and mixed-use frontage — retail, office, and light commercial single-phase service
Rural electrification — radial-feed single-phase extension where three-phase infrastructure is not justified
Street lighting and parks — dedicated single-phase pad-mount service
Small industrial single-phase loads — auxiliary equipment, controls, and single-phase motors
Latin American urban distribution — 12.47 kV and 13.8 kV single-phase pad-mount networks in Mexico, Central America, and the Caribbean
| Americas Buyer Concern | How This Product Addresses It |
|---|---|
| ANSI/IEEE C57.12.25 compliance | Designed to the governing single-phase pad-mount standard, ≤167 kVA, ≤34.5 kV class |
| UL Listing / cUL acceptance | UL Listed and cUL available; CSA option for Canada |
| DOE efficiency / lifecycle cost | DOE 2016 compliant; DOE 2027-ready configurations available |
| Loop-feed reliability for URD | Loop and radial feed on one platform, with 2-position switch or sectionalizing option |
| Public-area safety | Dead-front, tamper-resistant, lockable enclosure; IEEE C57.12.28 integrity; no exposed live parts |
| Voltage matching across Americas | 4.16 kV through 34.5 kV class, covering CFE, ICE, ETESA, ENEE, and Caribbean 12.47/13.8 kV ratings |
| Fire / environmental sensitivity | Natural ester（FR3-type）fluid option |
| Single-source factory build | Fuse, pressure relief, gauges, bushing wells integrated in one factory-assembled unit |
Every single-phase pad-mounted unit is built to order. Specify at inquiry:
Primary and secondary voltage ratings
Capacity（5–167 kVA standard; 250 kVA extended）
Loop or radial feed; dead-front or live-front
Winding material（copper / aluminum）
Insulating fluid（mineral oil / natural ester）
Fusing configuration（bayonet, isolation link, current-limiting backup）
BIL and impedance requirements
Enclosure finish and locking hardware
Certification package（UL, cUL, CSA, or combined）
Request a Quote — include your voltage class, kVA rating, feed configuration, and destination country. Our engineering team will return a specification-matched proposal with compliance documentation.
Does this transformer meet ANSI C57.12.25?
Yes. The single-phase platform is designed to IEEE/ANSI C57.12.25 for compartmental-type, self-cooled, single-phase pad-mounted distribution transformers, 167 kVA and smaller, 34.5 kV class and below.
Is UL Listing available for single-phase pad-mounts?
Yes. UL Listing and cUL are available. CSA is available for Canadian compliance.
Can I specify loop feed for U.S. residential and radial feed for Latin American projects?
Yes. Loop and radial feed are configuration options on the same single-phase platform, with 2-position switch or sectionalizing switch arrangements.
What is the maximum kVA for C57.12.25 scope?
C57.12.25 covers 167 kVA and smaller. We also offer 250 kVA as an extended-range option where project load requires it, outside the standard single-phase pad-mount scope.
What voltage classes match Mexico and Central America for single-phase?
12.47–7.2 kV and 13.8–7.957 kV are the most common single-phase pad-mount ratings in Mexico, Central America, and the Caribbean. 34.5–19.92 kV and 4.16 kV are also available.
Is natural ester fluid available?
Yes. FR3-type natural ester is available as an alternative to Type II mineral oil for fire-sensitive or environmentally regulated installations.
Ready to specify? Send your kVA rating, primary/secondary voltage, feed type, and destination market. We will confirm compliance configuration, lead time, and delivered pricing.
