Switch­ing the switches

Canal Boat - - Back Cabin -

QIs it pos­si­ble to use 240v house type light switches for my boat’s 12V LED spot­lights? SPLITTY, via the CB web­site

ATONY REPLIES… Yes it’s per­fectly pos­si­ble and we have done it for 17 years, but it is not best prac­tice.

House­hold switches are rated for AC: al­ter­nat­ing cur­rent, which turns it­self off for a split sec­ond 100 times a sec­ond as it al­ter­nates. So the in­stant you turn the switch off, the elec­tric­ity sup­ply­ing the switch turns it­self off, pre­vent­ing spark­ing as the con­tacts open. With bat­tery-sup­plied DC (di­rect cur­rent) there is no such turn-off, so the de­sign needs to pre­vent spark­ing and con­tact dam­age. Some mains switches may, in fact, be rated for DC, but I sus­pect most are not. Also the elec­tron­ics in­side those bulbs might cause a volt­age surge as you turn them off, mak­ing any spark­ing worse (but I feel this is un­likely).

The mains switches have am­ple in­su­la­tion for 12v, and with LEDs, the cur­rent is likely to be small; so sub­ject to the above, such switches can be used at your own risk. It would be good prac­tice to use ‘boot­lace fer­rules’ on the bare ca­ble strands where they screw into the switches.

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