I`m designing a control cabinet with a 60A output demand for heaters. The on/off switching of the heater will be done through a 24V/80A contactor(relay). The customer wants the main switch on the door. That requires 2x5x10mm2 wires to and from the door switch. Unfortunately, there is no space for the switch on the DIN rail with a long stick to the door. I offered 2 solutions: 1. Place the main switch on the side, not on the door. 2. The main switch operates only L1 for the control electronics and L2, L3 going strait to the MCB, and then to the contactor(relay), so I do not need to switch the 60A on the door, only the small current for the control electronics. Is this legal to do this way? My question is, which solution is the right one? Or if none, then how would you do it? Thanks!
From the safety perspective, it would be logical to disconnect all three phases with the main switch. Maintenance personnel would also expect/assume that it would be so.
Door-mounting of the main switch would only be an alternative to side-mounting without any added benefits. In fact, door-mounting would be more unsafe than side-mounting, considering the routing of the 10mm² cables with sufficient slack and the chances of exposure of personnel to live points.
A door-interlocked main switch would render the cabinet inherently safe and would also conform to safety norms worldwide (considering it as a product and not a one-off).
In my opinion, a door-interlocked main switch, to disconnect all three phases, would be the right choice.
It would be worth your while to redo the layout.