What's the difference between a fused and non-fused disconnect?
The difference is whether the switch also protects the circuit. A fused disconnect holds fuses that add overcurrent protection — it both cuts power and guards against shorts and overloads. A non-fused disconnect only opens and closes the circuit, relying on a breaker elsewhere for protection. Use fused where the equipment needs local protection, non-fused where an upstream breaker already covers it.
What size disconnect do I need — 30, 60, 100, or 200 amp?
Size the disconnect to the load it feeds. A 30-amp switch suits small motors, AC condensers, and light circuits. A 60-amp switch covers larger HVAC and subpanels. 100- and 200-amp switches feed services, big motors, and equipment panels. Pick a rating at or above the circuit's amperage — the disconnect must equal or exceed the breaker or fuse protecting it.
Which NEMA enclosure does a disconnect need?
The enclosure depends on where the disconnect mounts. A NEMA 1 enclosure is for dry indoor walls. A NEMA 3R enclosure is raintight for outdoor and damp locations — the most common for AC disconnects. A NEMA 4X enclosure resists washdown and corrosion in wet, coastal, or chemical areas. Match the rating to the environment the switch faces.
When does an HVAC unit need an AC disconnect?
An outdoor AC or heat-pump unit needs a disconnect within sight of it. The NEC requires a disconnecting means within sight and readily accessible at the equipment, so a technician can kill power before servicing. A non-fused 30- or 60-amp NEMA 3R pull-out is the typical choice. It mounts on the wall beside the condenser, not inside the panel.
How do I choose poles and voltage for a disconnect?
Two things set the rating: the supply and the load. Choose 2-pole for single-phase 120/240V circuits and 3-pole for three-phase 208, 240, or 480V power. Confirm the voltage rating covers your system — a 240V switch can't serve a 480V feeder. For a neutral, add a solid neutral kit or a switched neutral pole as the install requires.
Building the rest of the service? Overcurrent protection is in Circuit Breakers, and equipment surge protection in Surge Protective Devices.
