Hager ER120 - what does it do?

[endeavour]

I'm not sure I understand the wiring diagram on the front of the unit, nor what the switch is meant to do. Could anybody explain how it works?

Also is the switch meant to move, because it seems to be stuck in the auto position?

Thanks!

[Manul]

Seems to be a relay with two pairs of contancs, NO (normally open) and NC (normally closed). Operated by energizing A1 and A2 with 230V AC. Switch is probably a manual override, for testing purposes, not sure.

[tooki]

Manul is exactly right. The “auto” position is just the “normal” position (i.e. it operates as a relay controlled by the coil), while “on” and “off” manually override it.

[MarkT]

I suspect its useful for maintenance/servicing of equipment as an override to the normal operating mode.  Hopefully the lever is sprung to return to centre so you can't accidentally leave things overriden...

[tooki]

I suspect its useful for maintenance/servicing of equipment as an override to the normal operating mode.  Hopefully the lever is sprung to return to centre so you can't accidentally leave things overriden...

Based on their current catalog, I suspect the switch is specifically designed to stay on or off, which is the point of the switch: it’s an override.

They make other models which return from on to auto, but manual off stays off.

[endeavour]

Thanks all, that makes sense.