Safety Switch Ratings Chart
Disconnect safety switch sizes from 30 to 1200 amperes with their horsepower ratings — heavy-duty fusible with the standard and time-delay-fuse maximums at 240, 480, and 600 V, the non-fusible ratings, the general-duty 240 V table, and the general-duty vs heavy-duty decision chart. Values are the UL 98 listing ratings that Eaton, Square D, and Siemens publish in common; every cell here is confirmed across at least two of those catalogs, and the handful of cells where catalogs disagree are footnoted. The switch nameplate governs the install.
Heavy-duty fusible — HP ratings (std / max with time-delay fuses)
| Switch | 1φ 240 V std / max | 3φ 240 V std / max | 3φ 480 V std / max | 3φ 600 V std / max |
|---|---|---|---|---|
| 30 A | 1.5 / 3 | 3 / 7.5 | 5 / 15 | 7.5 / 20 |
| 60 A | 3 / 10 | 7.5 / 15 | 15 / 30 | 15 / 50 |
| 100 A | 7.5 / 15 | 15 / 30 | 25 / 60 | 30 / 75 |
| 200 A | 15 / 15 | 25 / 60 | 50 / 125 | 60 / 150 |
| 400 A | — | 50 / 125 | 100 / 250 | 125 / 350 |
| 600 A | — | 75 / 200 | 150 / 400 | 200 / 500 |
| 800 A | — | 100 / 250 | 200 / 500 | 250 / 500 |
| 1200 A | — | 100 / 250 | 200 / 500 | 250 / 500 |
Heavy-duty non-fusible — HP ratings
| Switch | 240 V | 480 V | 600 V |
|---|---|---|---|
| 30 A | 10 | 20 | 30 |
| 60 A | 20 | 50 | 60 |
| 100 A | 40 | 75 | 100 |
| 200 A | 60 | 125 | 150 |
| 400 A | 125 | 250 | 350 |
| 600 A | 200 | 400 | 500 |
| 800 A | — | 500 | 500 |
| 1200 A | — | 500 | 500 |
General-duty (240 V) fusible — HP ratings
| Switch | 1φ 240 V std / max | 3φ 240 V std / max |
|---|---|---|
| 30 A | 1.5 / 3 | 3 / 7.5 |
| 60 A | 3 / 10 | 7.5 / 15 |
| 100 A | 7.5 / 15 | 15 / 30 |
| 200 A | 15 / 15 | 25 / 60 |
| 400 A | — | 50 / 125 |
| 600 A | — | 75 / 200 |
General duty vs heavy duty
| Attribute | General duty | Heavy duty |
|---|---|---|
| Voltage class | 240 Vac (some 250 Vdc) | Up to 600 Vac; 250/600 Vdc |
| Ampere range | 30–600 A | 30–1200 A (bolted-pressure switches beyond) |
| Short-circuit rating (with fuses) | 10 kA with Class H/K; 100 kA with Class R, J, or T current-limiting fuses | 10 kA with Class H/K; 200 kA with Class R, J, T, or L |
| Enclosures | NEMA 1 and 3R only | NEMA 1, 3R, 12, 4/4X (painted, stainless, non-metallic), plus 7/9 hazardous-location variants |
| Fuse provisions | Class H/K standard; Class R with rejection kit | Class H/K/R standard with Class J provisions; 800–1200 A take Class L bolt-in |
| Construction | Quick-make/quick-break, HP rated | Adds visible double-break blades, arc chutes, defeatable dual cover interlocks, hookstick handles, auxiliary contacts |
| Where it belongs | Residential and light commercial — A/C units, appliances, lighting loads | Industrial and commercial motor loads, hostile environments, service continuity |
How to size a disconnect
Two checks, both mandatory. The ampere check: 115% of the motor's table full-load current (from the motor FLA chart), rounded up to the switch ladder — the rule and its exceptions live on the motor disconnect rules chart. The horsepower check: the switch's HP rating at your voltage must cover the motor, on the column matching your fuse type. The ampere math often lands on a switch whose standard HP rating falls short — that's the time-delay-fuse column's job, and it's why dual-element fuses are the default in motor circuits. The motor circuit data chart runs both checks for every standard motor.
Common questions
What do the two horsepower numbers on a safety switch mean?
Every fusible switch carries a dual HP rating: the standard rating, which applies with ordinary non-time-delay fuses, and a higher maximum rating that applies only when dual-element time-delay fuses are installed. A 30 A heavy-duty switch at 480 V is 5 HP standard but 15 HP with time-delay fuses — the fuse choice, not the switch hardware, is what unlocks the difference, because time-delay fuses ride through motor inrush at a smaller ampere size.
What size disconnect do I need for a 50 HP, 480 V motor?
By the NEC math: 65 A table FLC × 115% = 74.8 A minimum, so a 100 A switch. The HP ratings agree — a 100 A heavy-duty switch at 480 V is rated 25 HP standard and 60 HP with time-delay fuses, so it carries 50 HP only on the time-delay rating; with non-time-delay fuses you would need the 200 A switch. Check both the ampere rule and the HP line.
When is a general-duty switch acceptable instead of heavy-duty?
On 240 V systems in residential and light-commercial service — the A/C disconnect on a house wall is the classic general-duty install. The moment the system is 480 V, general duty is out (it is a 240 V class device). Heavy-duty is the default spec for industrial motor loads, anywhere you need NEMA 12/4X or hazardous-location enclosures, high fault current with Class R/J/T/L fusing, or auxiliary contacts.
Why does a non-fusible switch have a higher HP rating than the same size fusible switch?
At the small sizes it does — a 60 A heavy-duty switch at 480 V is 50 HP non-fusible but only 30 HP even with time-delay fuses. The fusible rating is limited by what fuse can both fit the switch and survive motor inrush; the non-fusible switch is rated purely on its blades' ability to break locked-rotor current, since something upstream provides the overcurrent protection. From 200 A up, the two converge.
Are safety switch HP ratings the same for every manufacturer?
Almost — the ratings are UL 98 listing values and Eaton, Square D, and Siemens publish matching tables nearly cell for cell. A few cells genuinely differ between catalogs (Square D currently lists 100 HP where others list 75 at 100 A/600 V; general-duty 600 A max is 200 HP for Eaton and Siemens but 150 for Square D). This chart prints the value at least two manufacturers agree on — the nameplate on the switch you actually install governs.
RUN THE NUMBERS
Run your whole job on the same numbers
These NORDIX tools are a taste of the full platform — bid pipeline, estimating, and job costing that carry your numbers from the first bid to the final invoice.
See what NORDIX does →