(How) can IEC-specification miniature circuit breakers be interlocked?

Question

A relatively common way of implementing a transfer or bypass/isolation function in North American electrical practice is to use mechanical means to interlock the handles of multiple circuit breakers or molded case switches so that they can't be both on at the same time. This can be done using a piece of metal retrofitted to a panelboard/loadcenter, or as part of a factory transfer switch assembly that uses circuit breakers or molded case switches as the electrical switching means.

However, the devices used to do this are designed around the North American busbar-mounted types of breakers. Breakers designed to the IEC standards typically mount to DIN rail instead, using a cable-in/cable-out construction, with a single row of breakers vs. the opposing-columns construction typical in North America. Is it possible to mechanically interlock this style of breaker (i.e. breaker A and breaker B cannot be on at the same time) without violating its approvals? If so, how is it done in practice?

Answer 1

Im German these are called Lastumschalter (loaded-operation selector switch). Smaller ones are available for DIN rail. They are never combined with overload or short circuit protection.

Hager HIM304 40A Lastumschalter

Answer 2

breaker A and breaker B cannot be on at the same time

I suspect this requirement most often arises in USA homes due to the use of split-phase supplies where alternating breakers are on separate phases and you can combine adjacent 120V breakers to produce a 240V circuit. This is a peculiarly American arrangement.

In the UK, I can't think of any reason I'd ever need to ensure that switching off my upstairs 240V lighting circuit also turned off my 240V cooker circuit.

If you have a backup generator or a solar installation, you have a transfer switch to handle that separately from your main panel.

If you need to isolate both neutral and live, you generally have dual-pole switch near the appliance (e.g. electric shower, alarm systems, etc). Thats a switch not a breaker and it isn't in the main panel but typically wall mounted like most switches.

You can get dual-pole MCBs but they are for isolating both live and neutral (not two phases) and I believe are only needed under special circumstances (e.g. TT system?)

I'm not familiar with industrial arrangements, presumably they use multi-pole breakers where needed. Perhaps these are designed as such rather than having linking kits added on?

Answer 3

I wouldn't expect to see this sort of mechanical interlock in a "normal" North American breaker panel. It is more likely to be seen in a custom assembly housing two breakers, and the mechanical interlock.

As long as the breaker handles are easily accessible, and move a reasonable distance between "Off" and "On", it should be possible to arrange a mechanical interlock - may need some special brackets around the breakers to support the interlock slider.

Answer 4

You can use motor reversing contactor. It has mechanical interlock, additionally you can make also an electrical interlock with the separate contacts wiring.

You have to add a selector switch and circuit breaker, that is the same for both sections.

EDIT:

In a similar way, you can get two contactors + additional mechanical interlocking kit (for that series of contactors) and you wire them on separate circuit breakers. Motor reverse contactor is simply a kit with two contactors, mechanical interlock and jumper busbar.

IMO, you won't find the device you are looking at, because the circuit breakers are protective devices, they are not meant for switching purposes, while switches, contactors are switching components.