American Rotary vs Phoenix Phase Converters: Sizing, Balance and Warranty From Their Own Documents
American Rotary and Phoenix Phase Converters both tell you to start with a rotary phase converter rated at twice your motor's horsepower. Both put a lifetime warranty on their rotary control panels. Their documents differ in four places:
- Hard-starting loads: Phoenix's Sizing Guide uses 2.5x the motor hp for a piston compressor. American Rotary's FAQ says to add 25 to 50% capacity but doesn't say to what. Added to its 2x figure, that works out to 2.5x to 3x the motor hp, by our arithmetic.
- Phoenix's other pages: its Sizing Wizard, its CNC guide and its pages for each converter size use different multipliers from its Sizing Guide. So two Phoenix pages can give different converter sizes for the same machine.
- Voltage balance: this is how closely the three output legs match. A lower figure means a closer match. American Rotary prints 0 to 5% in the spec table on its model pages, 2 to 5% in its FAQs, and 1 to 5% for its digital rotary converters, the units with its MicroSmart digital controller. Phoenix prints several figures, from 1% to 5%, on different pages for different product lines.
- The idler motor: this is the motor inside a rotary converter that spins to make the third leg. American Rotary's is a Baldor motor with Baldor's two-year warranty. Phoenix's has a three-year warranty from North American Electric Motors or Techtop.
At Built for Production, we read both makers' own documents in October 2026. Every figure below comes from them, and they're listed at the end. Where one maker's pages disagree, we show each figure, so you can check each maker's own numbers against your machine.
American Rotary vs Phoenix phase converters at a glance
| Item | American Rotary | Phoenix |
|---|---|---|
| Basic sizing rule | At least 2x the hp of your load (FAQs page) | 2x the hp of your largest motor (Phase Converter Sizing Guide) |
| Hard-starting loads | Add 25 to 50% capacity; the FAQ doesn't say to what | 2.5x for piston compressors, 3x for dust collectors (Sizing Guide) |
| CNC sizing | No separate multiplier published | 2x the spindle hp (CNC guide); 2.5x for some CNC machines (Sizing Guide) |
| Published voltage balance | 0 to 5% (model page spec tables); 2 to 5% (FAQs); 1 to 5% for digital rotary units (CNC page) | 1 to 5%, depending on product line and page |
| Control panel warranty | Lifetime (user manuals) | Lifetime (Warranty Policy page) |
| DIY panel (a control panel you pair with your own idler) | 1 year (AD-STK manual) | Excluded; no term printed in the documents we read |
| Idler motor | Baldor, two years | North American Electric Motors or Techtop, three years |
| Rotor (the spinning part inside the idler) | No separate term printed | Lifetime, for the original owner |
| Transferable | No | Not stated |
How does each maker size a rotary phase converter?
Both makers start at 2x the motor's hp for an ordinary load like a lathe. Each adds a different amount for hard-starting loads.
American Rotary's sizing rule
American Rotary's FAQs page says, "Choose a converter rated at least twice the Horsepower rating of your load." The next line reads, "For hard-starting loads (compressors, punch presses), add 25-50% capacity." Its blog post "A Beginners Guide to Sizing a Rotary Phase Converter for Your Machine Shop" gives the same 2:1 rule: "if you have a 10 HP motor then a 20 HP phase converter is needed."
American Rotary's user manuals give each unit two ratings: the largest single load, and the total load it carries with everything running. From the User Manual AD(X) Low Voltage 208-240V, R2.9:
| Unit | Largest load for optimal performance | Max total load running |
|---|---|---|
| AD/ADX 10 | 5 hp | 10 hp |
| AD/ADX 20 | 10 hp | 20 hp |
| AD/ADX 25 | 12.5 hp | 25 hp |
| AD/ADX 30 | 15 hp | 30 hp |
Phoenix's sizing rule
Phoenix's Phase Converter Sizing Guide, dated February 25, 2026, sorts loads into three groups:
- 2x: lathes, mills, drill presses, fans, centrifugal pumps, screw compressors, saws
- 2.5x: piston compressors, scroll compressors, loaded conveyors, submersible pumps, hydraulic presses, equipment that starts under load
- 3x: dust collectors, large industrial fans, flywheel-driven equipment
The guide says, "Always round up to the next available converter size." Phoenix's other sizing pages use different multipliers, shown in the worked example below.
A 10 hp lathe and a 10 hp piston compressor on each maker's rule
For a 10 hp lathe, both makers' main rules land on a 20 hp converter. For a 10 hp piston compressor, Phoenix's Sizing Guide gives 25 hp and American Rotary's FAQ gives 25 to 30 hp by our arithmetic. Here's the math:
| Machine | American Rotary | Phoenix |
|---|---|---|
| 10 hp lathe | 20 hp: 10 x 2 = 20 (FAQ). The AD/ADX 20 is rated for a 10 hp largest load | 20 hp: 10 x 2 = 20 (Sizing Guide) |
| 10 hp piston compressor | 25 to 30 hp: 20 x 1.25 = 25 and 20 x 1.5 = 30 | 25 hp: 10 x 2.5 = 25 (Sizing Guide) |
American Rotary's FAQ doesn't say what the 25 to 50% is added to. We added it to the 20 hp from its 2x rule, so confirm that starting number with American Rotary before you order. The 25 to 30 hp result points to the AD/ADX 25 or AD/ADX 30. American Rotary's manual rates those for a largest load of 12.5 hp and 15 hp, both above the compressor's 10 hp.
Phoenix's Sizing Guide says, "A 10 HP compressor may need a 25 HP converter, not just 20 HP." Phoenix's other pages give other answers for the same two machines:
| Phoenix page | Multiplier or rating as printed | 10 hp lathe | 10 hp compressor |
|---|---|---|---|
| Sizing Wizard | 2x for lathes ("Hard-start"); 1.75x for small lathes ("Medium-start"); 2.5x for air compressors ("Very hard-start") | 20 hp. A small lathe: 10 x 1.75 = 17.5, rounded up to 20 hp | 25 hp: 10 x 2.5 = 25 |
| The Complete Guide to Phase Converters for CNC Machines 2026 | 1.5x for manual lathes; 2.0x for air compressors | 15 hp: 10 x 1.5 = 15 | 20 hp: 10 x 2 = 20 |
| 20 HP Rotary Phase Converter page | GP20NL rated for "Hard" loads up to 10 hp and "a maximum 7.5 HP compressor" | GP20NL (20 hp) for a 10 hp CNC lathe, which the page counts as a "Hard" load | More than the GP20NL. The page names no larger size |
| 10 HP Rotary Phase Converter page | A 10 hp unit runs "any single three-phase motor up to 10 HP." For "CNC machines or motors with high inrush," "roughly 2× the spindle motor HP" | 10 hp for a manual lathe. A CNC lathe: 10 x 2 = 20 hp | No compressor figure |
| Homepage FAQ | "Add 50% headroom for hard-starting loads (compressors, large mills)" | No lathe figure | 15 hp: 10 x 1.5 = 15 |
Ask Phoenix which page applies to your machine before you order.
Running several machines at once changes the math at both makers. Our phase converter sizing guide covers that case. For a single 10 hp motor, our post on what size phase converter a 10 hp motor needs shows eight makers' answers.
What do American Rotary and Phoenix say about CNC machines?
Phoenix publishes a CNC sizing rule, and American Rotary doesn't. Both makers say how closely a CNC needs its voltage balanced. Both also point CNC buyers to particular product lines. Your CNC maker's manual sets the balance your machine accepts, so get that number first and compare each figure below against it.
Phoenix's Sizing Guide uses 2.5x for CNC machines with servo rapid traverse. That means the CNC's servo motors make fast positioning moves, which the guide says "create sudden, high current demands." Your CNC's manual or spec sheet tells you whether yours has it.
| Item | American Rotary | Phoenix |
|---|---|---|
| CNC sizing rule | None published. Its CNC page says, "You may want to go with a larger load than you currently require" | 2x the largest spindle hp (CNC guide); 2.5x with servo rapid traverse (Sizing Guide) |
| 10 hp spindle | No figure | 20 hp: 10 x 2 = 20 (CNC guide). With servo rapid traverse, 25 hp: 10 x 2.5 = 25 (Sizing Guide) |
| Balance a CNC needs, per the maker | "+/- 5% or better" (CNC page) | "within 2-3%" (CNC guide); "a maximum of 5%" (FAQs page) |
| Balance for its own units | 0 to 5% (model page spec tables); 1 to 5% for its digital rotary converters (CNC page) | +/-2% for its NL and PL rotary lines (datasheet) |
| Line it points CNC buyers to | AD series, for the balance requirement. ADX, which it says is "precise enough for CNC applications" (CNC page) | PL series, for "CNC machines, welders, or anything with sensitive electronics" (10, 15 and 25 HP pages). The 10 HP page also says, "Most shop and CNC owners want the GP10NL." The 20 HP page calls the GP20NL "the right choice when your largest CNC spindle is 10 HP or smaller" |
What voltage balance does each maker publish?
American Rotary prints three figures in three places. Its model pages list 0 to 5% in their spec tables, and its FAQs give 2 to 5%. Its CNC page gives 1 to 5% for its digital rotary converters, the units with its MicroSmart controller. American Rotary says that controller "monitors voltage every millisecond." Phoenix prints figures from 1% to 5% across its product lines. NL and PL are its two main rotary lines, which its pricing guide calls "Standard Rotary" and "Premium Rotary." Some Phoenix lines carry different figures on different pages. Here's each one, with its document:
| Product line or page | Figure as printed | Document |
|---|---|---|
| American Rotary converters, no product line named | Typically 2 to 5% between phases, under load | FAQs page |
| American Rotary digital rotary converters with MicroSmart (the AD series is one) | "precise voltage balance at 1-5%" | Guide to Choosing a Rotary Phase Converter for CNC Machining (blog) |
| American Rotary model pages we checked: AR 10, AD 10, ADX 10, AUL 10, AI 20 | Voltage Balance 0 to 5% | Three Phase Specifications table on each model page |
| Phoenix NL and PL | "+/-2%" | Datasheet NL - PL Models REV-223 |
| Phoenix NL | "3-5% voltage balance" | How Much Does a Phase Converter Cost (pricing guide) |
| Phoenix PL | "tighter voltage balance," no figure | Same pricing guide |
| Phoenix Standard Rotary | "within 3% leg-to-leg under load" | Homepage |
| Phoenix converters, on the GP20NL page | "factory-set to ±2% balance" | 20 HP Rotary Phase Converter page |
| Phoenix DualZone, which the pricing guide calls its "digital/electronic phase converter line" | "1-2% voltage balance" | Same pricing guide |
Phoenix's Static vs Rotary vs Digital Phase Converter blog also gives its GPX models "Superior (±1%)". That's a power quality rating, not a voltage balance figure.
Some of these figures say they hold under load, and some give no load condition. Ask each maker at what load its figure was measured.
What does each maker's lifetime warranty cover?
American Rotary and Phoenix both put a lifetime warranty on the rotary control panel. The idler motor has a shorter term from the company that made the motor: Baldor for two years at American Rotary, and North American Electric Motors or Techtop for three years at Phoenix. Phoenix's warranty also gives the idler's rotor a lifetime term for the original owner. To make an idler claim at either maker, first get the converter maker's OK in writing. Then take the motor to the motor maker's authorized service center.
| Part or term | American Rotary | Phoenix |
|---|---|---|
| Control panel | Lifetime, against defects in material and workmanship | Lifetime, against defects in materials and craftsmanship |
| Lines named | AR, AD, ADX, AI and AMP (warranty page). The AUL manual carries the same lifetime line | All rotary control panels |
| DIY panel | 1 year (AD-STK manual) | Excluded from the lifetime warranty |
| Idler motor | Baldor's two-year warranty | Three years, from North American Electric Motors or Techtop |
| Idler claims | A Baldor Authorized Service Center, with American Rotary's written OK first | A North American Electric Motors or Techtop Authorized Service Center, with Phoenix's written consent first |
| Rotor | No separate term printed | Lifetime, for the original owner |
| Panel claim shipping | You ship the panel to American Rotary. It pays return shipping on an in-warranty panel | You ship the panel to Phoenix. It pays return shipping on a panel under warranty |
| Installer | Licensed electrician (user manuals, warranty) | Licensed electrician (Warranty Policy page) |
| Main exclusions | Misuse, improper installation, incorrect line voltage, water damage, missing or altered serial numbers, unauthorized service | Misuse, improper installation, incorrect voltage supply, water damage, tampered or missing serial numbers, unauthorized repairs |
Phoenix's homepage FAQ says, "Wear items (contactors, fuses) are covered for 1 year." Its August 2025 Technical and Installation Manual says, "Normal wear items are excluded." Ask Phoenix which applies to your unit.
The FTC's Businessperson's Guide to Federal Warranty Law advises that an ad using "lifetime" say whose life it means, such as the life of the car a muffler is installed on, or the life of the original buyer. So check whose lifetime each maker's warranty means.
American Rotary's manuals warrant the panel "for a lifetime" and say the warranty "will remain with original purchaser/end user." If you sell the converter, the coverage doesn't go with it.
Phoenix's Warranty Policy page ties the rotor term to the original owner. Its homepage FAQ covers the control panel "for the lifetime of the converter." Phoenix's pages don't say whether the panel warranty passes to a second owner.
Our phase converter warranties by maker post sets these terms beside other makers'.
Is American Rotary or Phoenix UL listed?
Neither American Rotary nor Phoenix says all of its converters are UL listed. Here are their exact words, by document:
- American Rotary AUL page: "Each AUL converter is UL Listed by Underwriters Laboratories."
- American Rotary AUL manual, R2.8: "UL registered."
- American Rotary's manuals, the AUL manual included: "Not all American Rotary phase converters are UL listed." They add, "This is an option the customer must specify and additional charges will apply."
- Phoenix Warranty Policy page: "Phoenix Phase Converter may or may not be UL listed, based on customer preference, which may incur additional costs."
- Phoenix NL - PL datasheet: "UL LISTED AVAILABLE UPON REQUEST."
- Phoenix homepage: "UL-listed components." That describes parts inside the unit, not a listed converter.
Ask your local inspector what he requires before you order. Then ask the maker for the listing on the exact model in writing. American Rotary's AUL page says "UL Listed" and its AUL manual says "UL registered." Ask American Rotary in writing which listing status applies to the AUL unit you're buying.
What sizes does each maker sell?
American Rotary lists rotary lines from 5 hp up to 300 hp. Phoenix's datasheet covers its NL and PL rotary units from 3 to 100 hp.
| Item | American Rotary | Phoenix |
|---|---|---|
| Rotary lines and sizes | AR (Pro Series) 5 to 40 hp; AD 5 to 75 hp; ADX 5 to 300 hp; AUL 5 to 300 hp; AI 20 to 300 hp | NL and PL 3 to 100 hp (datasheet). Its product page names two lines instead: Standard, 2 to 100 hp, and Dual Zone, up to 200 hp |
| Voltages | 208-240V manuals for every line; 480V manuals for AD/ADX, AUL and AI, none for AR | 230V and 460V configurations (August 2025 manual) |
How loud are American Rotary and Phoenix converters?
American Rotary's FAQ says its converters run at 60 to 70 dB at every size. It gives no distance.
Phoenix's blog post "How Loud Are Phase Converters," dated December 19, 2022, says, "All of our phase converter models produce 43 Db from ten feet away."
Because American Rotary gives no distance, the two figures can't show you which unit is quieter. Our post on rotary converter noise puts each maker's figure with its conditions.
How to choose between American Rotary and Phoenix
Pick the figure that matters for your shop and compare that one:
- A hard-starting load like a piston compressor: compare Phoenix's 2.5x with American Rotary's 25 to 50% adder.
- A CNC machine: get the voltage tolerance from your CNC maker's manual. Compare it with the figure each converter maker prints for the exact product line. Then ask the maker at what load its figure holds.
- Several machines at once: American Rotary's manuals rate each unit for a largest load and a total load. Check your biggest motor against the first number and everything that runs together against the second. Phoenix's Sizing Guide takes the largest motor's hp times its load-type multiplier, then adds the hp of the other motors running at the same time.
- One machine with one motor: a VFD may also fit. Our guide to rotary vs digital phase converters vs VFDs compares the three types.
Documents named in this article
- American Rotary: FAQs page; A Beginners Guide to Sizing a Rotary Phase Converter for Your Machine Shop (blog); Guide to Choosing a Rotary Phase Converter for CNC Machining (blog); Warranty page; Manuals page; AUL product page; series, category and model pages for the AR, AD, ADX, AUL and AI lines; User Manual AD(X) Low Voltage 208-240V, R2.9; User Manual AUL Low Voltage 208-240V, R2.8; User Manual AD-STK Low Voltage 208-240V, R2.7; User Manual AR R2.7; User Manual AI R2.7 (warranty section)
- Phoenix Phase Converters: Phase Converter Sizing Guide: How to Size for Any Application (2026-02-25); The Complete Guide to Phase Converters for CNC Machines 2026 (2026-02-17); How Much Does a Phase Converter Cost: Complete Pricing Guide (2026-02-20); Static vs Rotary vs Digital Phase Converter: Which Is Right for You (2026-02-20); How Loud Are Phase Converters (2022-12-19); Sizing Wizard; 10 HP, 15 HP, 20 HP and 25 HP Rotary Phase Converter pages; homepage and homepage FAQ; FAQs page; Industrial Grade Rotary Phase Converter product page; Warranty Policy page; Datasheet NL - PL Models REV-223; Technical and Installation Manual (August 2025)
- Federal Trade Commission: Businessperson's Guide to Federal Warranty Law
Want both makers' rules run on your machine?
Our phase converter sizing calculator runs your nameplate numbers through American Rotary's and Phoenix's published rules and names the document for each. If you'd rather talk it through, call us at (855) 923-2610 or email contact@builtforproduction.com with your motor's nameplate numbers: horsepower, volts and full load amps. We'll show you each maker's answer and the arithmetic behind it. Questions about wiring or your shop's electrical service go to a licensed electrician and your local inspector. You can also reach us through our contact page.