15 HP Rotary Phase Converter — Who It's For

The GP15NL is the workhorse converter for mid-size machine shops, woodworking facilities, and agricultural operations running on single-phase utility power. If your shop has a mix of 3-phase equipment — a lathe, a milling machine, maybe a 5–7.5 HP air compressor — and you need them all running reliably off single-phase, this is your unit.

This converter is popular with:

• Home and small commercial machine shops running Bridgeport mills, engine lathes, surface grinders, and similar equipment
• Woodworking shops powering wide-belt sanders (up to 7.5 HP), shapers, planers, and large table saws
• Agricultural operations running grain augers, feed mixers, irrigation equipment, and grain bin fans
• Automotive and fabrication shops running tire changers, hydraulic presses, and smaller welders
• HVAC contractors testing and running commercial compressors up to 7.5 HP

What the GP15NL Can Power

At 15 HP total running capacity, you can operate a combination of 3-phase equipment as long as the total running horsepower doesn't exceed 15 HP and no single motor exceeds 7.5 HP at startup. Real-world examples:

• A 5 HP Bridgeport-style vertical mill + a 3 HP lathe + a 5 HP air compressor (running, not all starting simultaneously)
• A 7.5 HP wide-belt sander running alongside a 5 HP dust collector
• A 7.5 HP CNC router with coolant pump and vacuum system
• Up to three 5 HP motors running concurrently

Sizing Context

The GP15NL is ideal for shops where your largest single motor is 7.5 HP or less and total connected 3-phase load stays under 15 HP. If you're running a 10 HP motor or have hard-starting loads like scroll compressors or heavily-loaded CNC spindles, consider stepping up to a 20 HP or 25 HP converter, or look at our DualZone models designed specifically for hard-starting equipment.

Installation Overview — GP15NL

The GP15NL is an NL (No Link) model, meaning you supply your own idler motor and wire it to the converter panel. This is the most cost-effective option if you already have a suitable 3-phase motor or want to source one locally to save on shipping.

Key Installation Requirements

• Input Power: 230V single-phase (standard residential/commercial service)
• Minimum Service Size: 25 KVA (100A) — most homes with 200A service can accommodate this
• Breaker Size: 30A minimum, 80A maximum — use a double-pole breaker sized to your actual load
• Single-Phase Supply Wire: 4 AWG copper (for runs under 50 feet). For runs over 50 feet, upsize per NEC voltage drop tables — typically 2 AWG for 75–100 foot runs
• Idler Motor Wire: 8 AWG copper between the panel and the idler motor
• Idler Motor: You'll need a 15 HP, 1800 RPM, 3-phase motor (NEMA 254T frame). The motor weighs approximately 278 lbs (11" × 11" × 16")

Installation is straightforward for anyone comfortable with electrical work. Our installation manual walks you through every step with wiring diagrams. Average installation time is 2–4 hours. If you'd prefer a ready-to-go solution with the motor pre-wired and tested, check out the GP15PL (Pre-Linked) model.

Why Phoenix Phase Converters?

• Lifetime Warranty: Every Phoenix converter comes with a lifetime warranty — not 1 year, not 5 years, lifetime. If it fails, we fix or replace it. Period.
• 90-Day Money-Back Guarantee: Try it risk-free. If it doesn't meet your needs, send it back.
• American-Made: Built in Phoenix, Arizona by a team led by Daniel Floreancig, who has over 50 years of experience designing and building phase converters.
• Real Engineering: Our panels use properly sized capacitors, contactors, and circuit protection — not the undersized components you'll find in budget converters that burn out in a year.
• Expert Support: Call us and talk to someone who actually understands phase conversion. We'll help you size the right converter for your exact application.

Frequently Asked Questions — 15 HP Phase Converter

Can I run a 10 HP motor on a 15 HP converter?

You can run a 10 HP motor, but only if it's the only load on the converter and it's not a hard-starting application. The GP15NL's largest starting motor rating is 7.5 HP for standard across-the-line starting. If your 10 HP motor is lightly loaded at startup (like a fan or pump), it may work. Call us to discuss your specific setup — we'd rather help you get the right size than have you fight an undersized converter.

What's the difference between NL and PL models?

NL (No Link) means you provide the idler motor separately. PL (Pre-Linked) means the idler motor comes pre-wired and factory-tested with the panel — ready to install out of the box. The NL is less expensive and ideal if you already have a motor or want to buy one locally. The PL saves time and eliminates guesswork.

Do I need a separate subpanel for the converter?

Not necessarily. The converter connects to a dedicated breaker in your existing panel. However, you'll want a 3-phase subpanel or disconnect switches downstream of the converter to distribute power to your equipment. Many shops run a dedicated 3-phase subpanel with individual breakers for each machine.