Buy the best and biggest air compressor that runs on a single-phase 240V, 40A or 50A circuit, to feed a Hypertherm Powermax 45 XP plasma cutter — plus normal shop air, with headroom for a CNC table later.
From the Hypertherm Powermax45 XP Operator Manual (hypertherm.com, document HYP172110) — the primary source, not a reseller page:
| Process | Flow | Pressure |
|---|---|---|
| Cutting | 400 scfh ≈ 6.7 CFM | 85 psi min (while flowing) |
| Gouging | 350 scfh | 60 psi |
| Marking | 350 scfh | 55 psi |
| Supply limits | 80–100 psi recommended · 135 psi max · hose ≥ 3/8″ ID | |
A compressor is a continuous motor load. NEC sizing: conductors at 125% of motor full-load amps (FLA). That sets the ceiling:
| Circuit | Max motor FLA (×1.25) | Motor class that fits |
|---|---|---|
| 240V / 40A | ≤ 32A | 5 HP single-phase |
| 240V / 50A | ≤ 40A | 7.5 HP single-phase — the ceiling |
| — | > 40A | 10 HP single-phase needs 60A+. Out of scope. |
So the search is: the most delivered CFM from a 7.5 HP single-phase two-stage pump with nameplate FLA ≤ 40A.
| Unit | Delivered air | FLA | Fits | |
|---|---|---|---|---|
| PICK | EMAX 7.5 HP · 80 gal vertical EI07V080V1 · 2-stage, 4-cyl pressure-lube · 590 RPM |
31 CFM @ 100 psi | 38.9A | 50A ✓ (mfr-rated) |
| ALT | Quincy QT-7.5 · 80 gal vertical 1-ph 208/230V · 2-stage QT1 · 896 RPM |
23.6 ACFM @ 175 psi | ~31A* | 40–50A ✓ |
| 40A | EMAX 5 HP · 80 gal vertical ES05V080I1 · 2-stage pressure-lube · 730 RPM |
19 CFM @ 100 psi | 26.45A | 40A ✓ (mfr-rated) |
| OUT | EMAX 10 HP 1-ph (ES10V080V1) | 38 CFM | 52.9A | needs 60A ✗ |
| OUT | Big-box "5 HP peak" single-stage 60-gal units | ~13–15 CFM inflated | ~15–22A | fits, but undersized |
*Quincy nameplate FLA to be confirmed with the dealer — their published table lists ACFM but not amps. "Peak HP" units advertise inflated CFM-at-40-psi figures and can't hold 90 psi continuously under plasma load — excluded on principle.
EMAX 7.5 HP · 31 CFM · $3,008.49
Verified price + specs from the manufacturer's own spec table (FLA 38.9A, factory-rated 50A breaker). Four times the cutter's demand — the compressor idles at ~25% duty while cutting, which means dry air, long pump life, and a free path to a CNC table later.
Why not the Quincy: it's the better-built machine (slower pump, heavier cast iron) and the right pick if a local dealer relationship matters — but its price and nameplate amps aren't published, so it can't be the verified recommendation today. It's one dealer visit away from promotion.
Why "biggest": plasma punishes undersized compressors twice — pressure sag ruins cut quality mid-pass, and a pump running at 100% duty pumps heat and water into the line, which is what kills torches. Oversizing is the cheap insurance.
dryer ≈ $650 Eliminizer 128647 ≈ $400 Motor Guard M-60 ≈ $95 3/8″ hose ≈ $75 50A circuit ≈ $450 consumables ≈ $280
The manual is explicit: moisture and oil destroy torches and can void the warranty. The chain is tank → dryer → coalescing filter → cutter. One caution straight from the manual: ester-based synthetic compressor oils damage the Hypertherm filter bowl — standard oil only, or isolate with the dryer first. Estimates marked EST in the cart are ballparks to confirm at checkout.
- Started from the cutter, not the catalog. Pulled the Powermax45 XP Operator Manual direct from hypertherm.com (document HYP172110, 186 pp) and extracted the gas spec: flow, pressure, duty pattern, air-quality limits, filtration recommendation, warranty exposure.
- Set the electrical envelope before shopping. NEC 125%-FLA rule turned "40 or 50 amp" into hard motor classes: 5 HP max on 40A, 7.5 HP max on 50A, 10 HP impossible. This eliminated most of the market in one step.
- Manufacturer spec tables only. EMAX numbers (CFM, FLA, recommended breaker, pump RPM, price) come from the spec tables on emaxcompressor.com product pages; prices from their structured product data. Quincy ACFM from the QT-series table on quincycompressor.com.
- Dead ends, honestly marked. Ingersoll Rand and the big retailers (Northern Tool, Acme, Zoro) bot-blocked every retrieval path this session, so the IR 2475N7.5 (a legitimate ~24 CFM alternative) is parked, not evaluated — it can re-enter if brand preference appears. Anything not pulled from a primary source is flagged EST. in the cart.
- Cross-checked against the demand. Every surviving candidate was tested against 6.7 CFM @ 85 psi continuous: the pick delivers 4.6× demand, the 40A fallback 2.8×, both with the pump loafing.
- Quincy QT-7.5 nameplate FLA + dealer price — one call to the local distributor.
- Dryer model pick — any 25 CFM-class refrigerated dryer works; brand TBD at purchase.
- Electrician quote — the 50A run is ballparked at $450; site conditions decide.
- IR 2475N7.5 — parked (specs unverifiable this session), re-enter only if wanted.