25 kVA Transformers

How Many Amps Can a 25 kVA Transformer Handle?

Full-load amperage depends on the secondary voltage and whether the unit is single-phase or three-phase. Use the following standard formulas:

Single-phase: Full-Load Amps = kVA × 1,000 ÷ Secondary Voltage

Three-phase: Full-Load Amps = kVA × 1,000 ÷ (Secondary Voltage × 1.732)

25 kVA Transformer Full-Load Amps Reference Table

These are continuous full-load values. Per NEC Article 450, feeder and overcurrent protection must be sized at 125% of the transformer’s rated full-load current for continuous operation. Always verify conductor sizing per NEC Table 310.15 for the applicable voltage and ambient conditions.

25 kVA Transformer Voltage Configurations Available

Based on our actual product inventory, Bruce Electric stocks and sources 25 kVA units across a broad range of primary-to-secondary voltage configurations. The following configurations are confirmed available:

Single-Phase Configurations

Three-Phase Configurations

Availability varies by manufacturer and configuration. Contact Bruce Electric for configurations not shown, specialty voltage combinations, or multi-tap requirements.

25 kVA Dry Type Transformer

Dry type construction is standard throughout Bruce Electric’s 25 kVA inventory. These transformers use air as the cooling medium and require no liquid containment infrastructure, making them suitable for most commercial and industrial installations.

Ventilated Dry Type

Available in NEMA 1 and NEMA 2 enclosures, ventilated transformers allow air circulation through the enclosure for efficient cooling. They are commonly used in clean, dry indoor electrical rooms and mechanical spaces.

Encapsulated Dry Type

Encapsulated transformers feature resin-sealed windings that protect against moisture, dust, condensation, and corrosive environments. These units are commonly specified for outdoor installations, food processing facilities, wash-down areas, and harsh industrial environments.

All applicable new units comply with current DOE 2016 efficiency requirements for low-voltage dry type distribution transformers.

25 kVA Single-Phase vs. Three-Phase: Which Do You Need?

Single-phase 25 kVA transformers are the most common configuration in our inventory. They are appropriate when:

1. The downstream load is single-phase, such as lighting, receptacles, small HVAC, or single-phase machinery.

2. Branch circuit or panel feed requirements do not exceed approximately 104 amps at 240V secondary.

3. The application involves a sub-panel, lighting panel, or isolated equipment feed.

Three-phase 25 kVA transformers are appropriate when:

1. Downstream loads are three-phase, such as motors, three-phase HVAC, VFDs, or three-phase distribution panels.

2. The installation requires a balanced three-phase secondary.

3. Medium voltage step-down, such as 4160V to 480Y/277V, is needed for three-phase distribution.

Bruce Electric’s three-phase 25 kVA inventory includes units from Jefferson Electric, Rex Power Magnetics, and Acme Electric, covering both low-voltage and medium-voltage primary configurations.

Step-Up vs. Step-Down: 25 kVA Applications

Step-down transformers reduce voltage from a higher primary to a lower secondary. The vast majority of 25 kVA applications are step-down: 480V or 600V primary stepped down to 120/240V secondary for panel feeds, lighting circuits, equipment connections, and general-purpose distribution.

Step-up transformers increase voltage; for example, taking a 190/200/208/220V primary up to 380–480V secondary. Bruce Electric’s inventory includes units specifically configured for step-up applications, such as Hammond Power Solutions Q025XEKF with 190/200/208/220/240V primary and 380/400/415/440/480V secondary, commonly used for exporting equipment to higher-voltage markets or feeding European-standard machinery.

Many 25 kVA dry type transformers support reverse-feed operation for step-up use, but this must be confirmed with the specific manufacturer before installation. Not all insulation classes and winding configurations support reverse-feed.

25 kVA Transformer Specifications Overview

The following table summarizes key specification parameters across our 25 kVA inventory. Exact values vary by manufacturer, model, and configuration.

25 kVA Transformer Weight

Transformer weight varies by enclosure type, voltage class, and winding material.

Always consult manufacturer submittals for certified dimensions and weight before planning installation, rigging, floor loading, or conduit routing.

25 kVA Transformer Applications

A 25 kVA transformer is commonly used across commercial, industrial, and OEM power distribution systems, including:

1. Commercial Buildings: Sub-panels, lighting systems, HVAC equipment, and tenant electrical distribution where 480V service is stepped down to 120/240V.

2. Manufacturing & Industrial Facilities: Machine tools, conveyors, motor loads, and general-purpose equipment requiring reliable voltage conversion.

3. Retrofit & Replacement Projects: Upgrading aging transformers without redesigning the existing electrical distribution system.

4. Outdoor Installations: NEMA 3R and encapsulated units for equipment pads, parking facilities, and exterior distribution points.

5. Medium-Voltage Distribution: 2400V and 4160V primary applications requiring localized step-down to utilization voltages.

6. OEM & Packaged Equipment: Integration into control panels, skid-mounted systems, and custom electrical assemblies.

7. Export & International Applications: Multi-tap and specialty voltage configurations supporting global equipment and international power requirements.

Installation Considerations for 25 kVA Transformers

Air clearances: Dry type transformers require minimum clearance on all sides per NEC Article 450 and the manufacturer’s installation instructions. Ventilated units need unobstructed airflow paths; never install against a wall without adequate side and top clearance.

Overcurrent protection: Per NEC 450.3, primary overcurrent protection for transformers with supervised installations must be sized appropriately. For most 25 kVA units, primary protection is rated based on the primary full-load current; confirm with the applicable NEC table for the installation type.

Conductor sizing: Size primary and secondary conductors per NEC 310.15 based on full-load current at the applicable ambient temperature. Use the correct ampacity table for copper vs. aluminium conductors.

Ventilation: In enclosed electrical rooms, confirm that ambient temperature stays within the transformer’s rated operating range, typically 40°C maximum. Forced ventilation may be required in tight mechanical rooms.

Taps: Most 25 kVA units in our inventory include 2 to 6 taps at 2.5% above or below rated primary voltage (FCAN/FCBN). Taps allow fine voltage correction without additional equipment, which is particularly useful when utility voltage runs consistently high or low.

Encapsulated units outdoors: For outdoor or wet-location installation, specify NEMA 3R or NEMA 3R Encapsulated units. Standard NEMA 1 or NEMA 2 ventilated units are indoor-only.

How to Select the Right 25 kVA Transformer

Use this procurement checklist to specify the correct unit:

1. Confirm kVA requirement. Is 25 kVA actually the right size? Add up your connected load in watts or VA, divide by the secondary voltage, and divide by 1.732 for three-phase to get required amps, then convert back to kVA. Use our kVA Calculator to verify sizing.

2. Single-phase or three-phase? Identify whether downstream loads are single-phase or three-phase. Most 25 kVA applications at this capacity are single-phase.

3. Primary voltage. What is the available supply voltage: 480V, 208V, 600V, 277V, or something else? This determines which models are eligible.

4. Secondary voltage. What does the downstream panel or equipment require: 120/240V, 208V, or another configuration?

5. Indoor or outdoor? Indoor installations typically use NEMA 1 or NEMA 2 ventilated enclosures. Outdoor or wet-location installations require NEMA 3R or encapsulated construction. For more detail, see our guide on indoor vs. outdoor dry type transformer installation.

6. Environment. Dusty, humid, wash-down, or corrosive atmospheres require encapsulated construction.

7. Copper or aluminium windings? Aluminium is standard and cost-effective for most applications. Copper is preferred for critical or high-cycle environments.

8. Taps required? If utility voltage commonly runs off nominal, specify a unit with sufficient tap range to compensate.

9. Export or international? Specify 50/60 Hz dual-frequency export models where required.

Not sure which configuration fits your application? Contact Bruce Electric; our team can help you match load requirements to the right unit from our confirmed inventory.

Frequently Asked Questions

Q1. How many amps is a 25 kVA transformer at 240V?

A 25 kVA transformer delivers approximately 104 amps at 240V single-phase secondary voltage.

Q2. What is the difference between a 25 kVA single-phase and three-phase transformer?

Single-phase transformers serve lighting, receptacle, HVAC, and panel loads. Three-phase transformers are designed for motors, manufacturing equipment, VFDs, and three-phase distribution systems.

Q3. What does a 25 kVA dry type transformer weigh?

Depending on enclosure type and voltage class, a 25 kVA dry type transformer typically weighs between 100 and 350 pounds.

Q4. Can a 25 kVA transformer be used outdoors?

Yes. Outdoor installations require a NEMA 3R, NEMA 3R encapsulated, or similarly rated enclosure designed for weather exposure.

Q5. Are used 25 kVA transformers available?

Yes. Used, surplus, and reconditioned 25 kVA transformers are available through Bruce Electric’s custom sourcing and RFQ process, although they are not listed online.

Why Source from Bruce Electric?

Bruce Electric Equipment Corp. has been supplying industrial and commercial electrical equipment for over 50 years. We are not a marketplace or a broker; we are a stocking distributor of new electrical equipment with deep expertise in transformer sourcing for contractors, engineers, procurement teams, and facility managers.

1. New inventory, sold online. Our 25 kVA transformer listings reflect actual new-unit inventory from top manufacturers. No bait-and-switch, no gray-market substitutions.

2. Custom sourcing for used and reconditioned units. If budget or lead time requires a used, surplus, or reconditioned 25 kVA transformer, contact us directly. We do not list used equipment online, but we can source and verify units through our RFQ process, available upon request.

3. Broad configuration coverage. With 95 SKUs across 8 major manufacturers, Bruce Electric offers more 25 kVA configuration options than most electrical distributors, from standard 480V to 120/240V units to 4160V medium voltage step-downs and international export models.

4. Fast shipping on in-stock units. New units ship promptly from our stocking locations. Contact us for lead times on specific models and configurations.

Relevant Technical Reading

1. Dry Type Transformer Testing & Troubleshooting Guide

2. Dry Type Transformer Cooling Explained

3. Transformer Losses & Efficiency Guide

4. Transformer Cores: Materials, Design and Performance