Most commercial buildings were built decades ago, long before hydraulic elevators became standard. Many of these structures have only single-phase electrical service — which creates a real problem when it comes time to install or upgrade an elevator. Three-phase power is required for virtually all modern commercial elevator motors, and the utility company's quote to bring in a three-phase service is often eye-watering.
There's a better solution: a properly sized rotary phase converter paired with a step-down transformer, installed as a complete power package. Here's how it works — and how we helped a Montessori school solve exactly this problem.
The Milton Montessori Project: 40 HP Hydraulic Elevator, 208V 3-Phase
When Milton Montessori School needed to install an ADA-compliant hydraulic elevator in their multi-story building, they ran into an immediate obstacle: the building's electrical service was single-phase only, and the elevator manufacturer specified a 40 HP hydraulic unit requiring 208V three-phase power.
The project called for two pieces of equipment working together:
- A GP100NLT rotary phase converter — our 100 HP no-load-transfer unit, sized to handle the 40 HP elevator motor with appropriate safety margin and the inrush characteristics of hydraulic pump starts
- A 75 kVA step-down transformer — to convert the 240V single-phase utility input down to the 208V three-phase voltage the elevator system required
The combination gave the elevator clean, stable 208V three-phase power from a building that had never seen three-phase in its life. The installation passed inspection on the first visit.
Why Elevators Need Rotary Phase Converters (Not Static or VFD Solutions)
Hydraulic elevator systems are complex loads. They include the main hydraulic pump motor, control logic boards, valve solenoids, and safety systems — all of which need clean, balanced three-phase power.
Static phase converters — the inexpensive capacitor-only units — don't produce a true third leg. They generate an approximation that's fine for simple motors but causes problems with elevator controls, drive boards, and safety monitoring systems. Elevator OEMs and code inspectors typically reject static converter installations.
A rotary phase converter generates a true, utility-quality third phase using a rotating idler motor. The output is clean enough for sensitive elevator electronics and meets the power quality requirements that elevator manufacturers and ASME A17.1 inspectors expect.
ASME Code Compliance and UL Listing
If you're installing an elevator with a phase converter, code compliance matters. Here's what to know:
- ASME A17.1 (the Safety Code for Elevators and Escalators) requires that the power supply to the elevator meet the manufacturer's voltage and balance specifications. A properly sized rotary phase converter satisfies this requirement — a static converter typically does not.
- UL listing of the converter matters for AHJ (Authority Having Jurisdiction) approval. Phoenix Phase Converters GP series units are designed and built to meet applicable UL standards — ask us for documentation when submitting your permit package.
- Phase loss protection is critical. Our GP series includes phase loss detection, which shuts the converter down if any phase drops out — protecting the elevator motor and control systems from damage.
Sizing a Phase Converter for Your Elevator
For hydraulic elevator applications, we recommend a 2x multiplier on the pump motor horsepower:
- 10 HP elevator pump → GP20 or GP25 phase converter
- 15 HP elevator pump → GP30 phase converter
- 20 HP elevator pump → GP40 phase converter
- 25 HP elevator pump → GP50 phase converter
- 40 HP elevator pump → GP75 or GP100 phase converter
If the elevator requires 208V (rather than the more common 240V), you'll need to add a transformer to the package. We can spec and supply the transformer as part of a complete solution.
Do You Also Need a Transformer?
Most single-phase utility service in North America runs at 240V. Many commercial elevators, particularly older units or those installed in buildings designed for light commercial use, require 208V three-phase. These are two different voltages — 240V three-phase and 208V three-phase are not interchangeable without a transformer in between.
If your elevator specifies 208V 3-phase, you'll need:
- A rotary phase converter sized for the motor HP (input: 240V single-phase, output: 240V three-phase)
- A step-down transformer (input: 240V 3-phase, output: 208V 3-phase)
We source and supply both components and can provide a packaged solution with matched specs. This simplifies your permitting, reduces installation complexity, and gives you a single point of contact for warranty support.
Built for the Long Haul
An elevator runs every day for decades. The power supply needs to be equally durable. Our GP series rotary phase converters are built in Phoenix, Arizona with TEFC cast-iron motors and NEMA 4 weatherproof enclosures. Every unit carries a lifetime warranty — so the power supply you install today is covered for the life of the building.
Let's Talk About Your Elevator Project
Whether you're installing a new elevator, upgrading an existing one, or troubleshooting a power quality issue with an elevator that's already in service, we can help you design the right phase converter and transformer package.
Call us at 800-417-6568 or visit phoenixphaseconverters.com to discuss your project. We'll size the equipment, provide the documentation you need for permits, and make sure your elevator has reliable three-phase power from a single-phase source.