Guardian angel for medical devices and systems

The DIN EN 60601-1 standard specifies the basic requirements for medical electrical equipment (ME equipment) safety, including its essential performance characteristics. In section 8.11.5, it also explicitly defines the requirements for overcurrent protection: All protection class I and protection class II with functional earth terminal ME devices must be all-pole-protected without exception. For medical devices with a 230 V AC mains connection, this means that an overcurrent protection element must be provided in both the phase conductor and the neutral conductor. However, the type of overcurrent protection is not specified in the standards. This means: The device developer is free to decide whether to use fuse protection or circuit breakers. 

Only multipole circuit breakers safely disconnect the live phase conductor

The manufacturers of such an ME device have three options. Either they use two fuses or two single-pole circuit breakers or one double-pole circuit breaker. But do all three solutions offer the same level of protection and safety? Clear answer: No.

It is often overlooked that fuses and single-pole circuit breakers only provide a single pole physical isolation in the event of an overcurrent. The reason is that only the slightly faster overcurrent protection element trips in the event of a failure, while the slower twin device remains in the “ON” state. The interruption of the live phase conductor is therefore not guaranteed. The safest solution is the two-pole circuit breaker. This is the only way to guarantee double-pole physical isolation in the event of a fault, preventing dangerous potential carry-over in medical devices and systems.

In accordance with IEC EN 60601-1 section 8.11.1, each ME device must also be equipped with a device that disconnects all poles of its circuits from the mains supply simultaneously. The ideal solution are multi-pole circuit-breaker/switch combinations with a dual function, such as the 2-pole 3120 or 3130 circuit breakers with rocker switch from E-T-A. In single-phase AC circuits, they not only fulfil the function of the 2-pole circuit breaker but also serve as 2-pole mains switch. For manufacturers of ME devices, this combination significantly reduces installation and cabling costs and space requirements, as they only need to install a single component for both the on/off switch and overcurrent protection function. This also increases overall reliability, as fewer individual components also mean fewer sources of error. An additional benefit: Fewer components always simplifies purchasing logistics.