HVAC Phase Converters
Reliable Power for Air Conditioners, Chillers & Compressors
✅ Lifetime Warranty
🇺🇸 Made in USA
⚡ 50+ Years Experience
📞 Free Sizing Help
Running commercial HVAC equipment on single-phase power? HVAC compressors are among the most demanding three-phase loads — they start under full refrigerant pressure, draw massive inrush current, and cycle on and off automatically throughout the day. You need a phase converter built specifically for that kind of abuse.
Phoenix Phase Converters has been manufacturing industrial-grade rotary phase converters for HVAC applications since 1974. Our converters deliver the raw starting torque that compressors demand, with AutoStart capability for fully automatic thermostat-controlled operation — backed by a lifetime warranty and over 50 years of engineering expertise.
Why HVAC Compressors Need Rotary Phase Converters (Not VFDs)
HVAC compressors are fundamentally different from most three-phase equipment, and they require a specific type of conversion:
💥 Hard Starting Loads
Compressors start under full head pressure — the refrigerant doesn't decompress just because the compressor shut off. This means startup current can reach 6-8x the rated amperage. Rotary phase converters handle this effortlessly; VFDs often can't.
🔒 Hermetically Sealed Motors
Most HVAC compressors use hermetically sealed motors cooled by the refrigerant itself. VFDs produce harmonic distortion that generates excess heat in these motors — heat that can't be dissipated properly, leading to premature compressor failure.
🛡️ Warranty Protection
Most major compressor manufacturers (Copeland, Carrier, Trane, Bitzer) explicitly void their warranty if a VFD is connected to a hermetic compressor. A rotary phase converter produces true sinusoidal power that preserves your equipment warranty.
🔄 Automatic Cycling
HVAC systems cycle on and off based on thermostat demand — sometimes dozens of times per day. Our AutoStart phase converters sense when the compressor needs power, start automatically, and shut down when the cycle is complete.
🏭 Multiple Units
One properly sized rotary converter can power multiple compressors, condenser fans, and blower motors through a three-phase sub-panel — far more efficient than individual VFDs on each unit.
HVAC Phase Converter Sizing Guide
💡 Sizing Tip: For HVAC compressors, we recommend sizing the converter at 1.5x to 2x the compressor motor horsepower. This accounts for the extreme inrush current during locked-rotor starts under full refrigerant pressure. Undersizing a converter for an HVAC application is the most common mistake we see — and it leads to nuisance tripping and compressor damage.
AC Tonnage to Phase Converter Sizing
| AC System Tonnage | Typical Compressor HP | Recommended Converter Size |
|---|---|---|
| 2-3 Ton | 2-3 HP | 5 HP Converter |
| 4-5 Ton | 4-5 HP | 7.5-10 HP Converter |
| 7.5 Ton | 7.5 HP | 15 HP Converter |
| 10 Ton | 10 HP | 15-20 HP Converter |
| 15 Ton | 15 HP | 25-30 HP Converter |
| 20 Ton | 20 HP | 30-40 HP Converter |
| 25 Ton | 25 HP | 40-50 HP Converter |
| 30+ Ton | 30+ HP | 50-75 HP Converter |
Note: These are general guidelines. Actual compressor HP varies by manufacturer, system design, and refrigerant type. Call us at 800-417-6568 for free sizing based on your specific equipment nameplate data.
HVAC Applications We Power Every Day
❄️ Commercial Air Conditioning
Rooftop units, split systems, and packaged AC units for retail stores, restaurants, offices, churches, and warehouses.
🧊 Cold Storage & Refrigeration
Walk-in coolers, walk-in freezers, blast freezers, and cold storage warehouses. These systems run 24/7 and need rock-solid three-phase power.
🔥 Heat Pumps
Three-phase heat pump systems for commercial buildings. Our converters handle the reversing valve cycling and defrost cycles without issue.
💧 Chillers
Water-cooled and air-cooled chillers for process cooling, server rooms, and building climate control.
🌬️ Ventilation & Air Handling
Large blower motors, make-up air units, and rooftop ventilation systems that run continuously.
🌾 Agricultural HVAC
Greenhouse climate control, poultry house ventilation, dairy cooling systems, and grain drying equipment.
Recommended HVAC Phase Converter Models
NL Series — Standard Rotary
230V to 230V
Our workhorse model for HVAC applications. The NL series converts single-phase 230V to balanced three-phase 230V power. Features a NEMA 4 sealed enclosure that withstands outdoor installation, TEFC cast iron generator, voltage monitor, and automatic restart after power outages. For manually controlled HVAC systems or systems with a dedicated operator.
View Collection →AutoStart Series — Fully Automatic
Top Choice for HVAC
The top choice for HVAC. AutoStart converters sense when your compressor's thermostat calls for cooling (or heating) and automatically start the phase converter. When the thermostat is satisfied, the converter shuts itself down — saving energy and reducing wear. No operator needed — just set your thermostat and forget it.
View Collection →NLT Series — Step-Up
230V to 460V
Many commercial HVAC systems run on 460V three-phase power. The NLT series converts single-phase 230V to three-phase 460V with a built-in step-up transformer — no separate transformer required. Available with AutoStart for fully automatic operation.
View Collection →Why AutoStart Is Essential for HVAC
Here's the scenario: It's 2 AM. Your building's thermostat calls for cooling. Without AutoStart, your phase converter just sits there — powered off. Your compressor tries to start, fails, and your building heats up overnight.
✅ With AutoStart: The converter detects the thermostat's call for power, starts itself within seconds, powers the compressor through its full cooling cycle, then shuts down when the thermostat is satisfied. This happens automatically, dozens of times per day, 365 days a year. It's the only real option for unattended HVAC operation.
Installation Considerations for HVAC Phase Converters
1. Outdoor Rated: All Phoenix Phase Converters feature NEMA 4 sealed enclosures suitable for outdoor installation near rooftop HVAC units or compressor pads.
2. Wire Sizing: Use the correct wire gauge for both the single-phase input and three-phase output. HVAC compressor startup draws significant current — undersized wiring causes voltage drop and compressor issues.
3. Disconnect Requirements: Install proper disconnects per NEC code. Your electrician should install a single-phase disconnect at the converter input and a three-phase disconnect at the compressor.
4. Sub-Panel for Multiple Units: If powering multiple HVAC units, install a three-phase sub-panel to distribute power from a single converter. This is far more economical than individual converters for each unit.
Frequently Asked Questions — HVAC Phase Converters
Can I use a static phase converter for my HVAC compressor?
We strongly advise against it. Static converters produce an unbalanced third phase that causes compressors to run hot and fail prematurely. Hermetic compressors are especially vulnerable because they can't dissipate the extra heat. Always use a rotary phase converter for HVAC compressors.
Will a phase converter void my compressor warranty?
A quality rotary phase converter will not void your warranty — it produces true sinusoidal three-phase power indistinguishable from utility power. VFDs, on the other hand, are often explicitly excluded from compressor warranties due to harmonic distortion.
How much can I save vs. extending utility three-phase?
Utility three-phase extensions typically cost $20,000-$150,000+ depending on distance from the nearest three-phase line. A rotary phase converter sized for most commercial HVAC systems costs $2,000-$12,000 — savings of 80-95%. Plus, it's portable if you relocate.
Get Expert HVAC Phase Converter Sizing — Free
Every HVAC installation is different. Send us your compressor nameplate data (or snap a photo of it), and our engineers will size the right converter — including AutoStart configuration — at no charge.
📞 800-417-6568
Phoenix Phase Converters — Powering HVAC systems since 1974. Made in the USA with a lifetime warranty.