Buyer's guide to load break switches and switch-disconnectors: where they fit in a panel, how they differ from fuses, current rating and how to specify one.
A load break switch (often called a switch-disconnector, or in its fused form a switch-fuse) is a manual switching device that safely makes and breaks load current under normal operating conditions. In plain terms it lets a panel builder or maintenance electrician de-energise a circuit for work, or switch a feeder on and off, without pulling the main supply. Crucially, it is not a protective device: a load break switch does not trip on overload or short circuit. Protection comes from the upstream breaker or fuse; the load break switch provides visible isolation and controlled switching. IEC 60947-3 is the standard that governs these switches and disconnectors.
In a typical low-voltage board the load break switch usually sits just downstream of the main incomer breaker, or it is the main switch feeding the whole board. Common placements:
These terms get used interchangeably, but the differences change what you order:
| Device | Makes / breaks load | Short-circuit protection | Typical use |
|---|---|---|---|
| Load break switch | Yes (normal load) | No | Switching + isolation of a feeder |
| Isolator / disconnector | Off-load only | No | Visible isolation for safety |
| Switch-fuse (fusible) | Yes | Yes (via fuse) | Switching + fault protection |
| MCCB | Yes | Yes (trip) | Protection + switching of a circuit |
If you need fault protection, you need a fuse or breaker upstream (or a fused switch). A plain load break switch only isolates and switches.
A non-fusible load break switch isolates and switches but relies on a separate protective device. A fusible switch (switch-fuse) carries the fuse inside the switch body, so a short circuit is cleared by the fuse while the switch still gives you a visible break and a padlockable handle. Choose the fusible version when there is no separate breaker in the circuit, or where you want a single compact isolating-plus-protecting device. Note that a switched fuse still does not give an adjustable trip — it protects to the fuse characteristic only.
Size on the circuit's continuous current (In), not the motor or transformer nameplate peak. Two points matter:
Use the table as a starting point for common feeder sizes:
| Feeder load | Suggested rating | Poles |
|---|---|---|
| Lighting / small panel, ≤32 A | 32–40 A | 2P or 4P |
| Sub-feeder, 32–63 A | 63 A | 3P or 4P |
| Motor / compressor, 63–125 A | 125 A (AC-23) | 3P or 4P |
| Main incomer, 160–250 A | 160–250 A | 4P |
Match the pole count to the supply. Single-phase needs 2-pole; three-phase needs 3-pole, and if the neutral must be switched (TN-S/TT systems, or to fully isolate a 4-wire load) you need 4-pole. The handle deserves attention: a door-mounted, padlockable rotary handle is the norm for a main switch, and interlock it with the enclosure so the door cannot open while the switch is ON. For outdoor or wash-down areas, specify the IP-rated handle and shaft seal.
ELEHPD supplies load break switches and switch-disconnectors from 20 A to 250 A in 2-, 3- and 4-pole versions, non-fusible and fusible, with IEC 60947-3 compliance and door-interlocked handles, ready to drop into your panel alongside our MCCBs, contactors and busbar systems.
An isolator (disconnector) is for off-load isolation only — it should not make or break current. A load break switch can safely switch normal load current on and off as well as isolate, so it can be used for routine switching, not just safety isolation.
No. A plain load break switch has no trip mechanism. Fault protection must come from an upstream MCCB or, in the fused version, from the fuse built into the switch body.
Choose the fusible version when the circuit has no separate breaker, or when you want isolation and short-circuit protection in one compact unit. Remember it protects only to the fuse characteristic — there is no adjustable trip.
Use 2-pole for single-phase loads, 3-pole for three-phase where the neutral stays connected, and 4-pole when the neutral must also be switched or isolated (common in TN-S/TT systems and for fully isolating 4-wire loads).
Send the ratings, dimensions and quantities you are working to and we will confirm the closest match from the ELEHPD catalogue, the compliance documents available for it and the lead time. OEM branding, private model numbering and buyer-specific cartons are available on qualified volumes.