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Using AC Switches and Sockets for DC 12v or 24V Systems

by Ken Harbour on September 1, 2014

Let take a look at what to consider when thinking of using regular AC household Switches and Sockets for DC Systems.

We are often asked by DIY’ers if it is possible to be using AC switches and sockets for DC 12v or 24V systems. The answer is yet, but…

Folks living wholly ‘Off Grid’ will either be using dedicated DC to AC inverters for to provide power for most items, often including their lighting. However, in many cases one may be taking advantage of the higher efficiency of using specialist DC lighting direct from a battery /PV system leaving the inverter device(s) to power the larger consumer devices.

The first thing to find out when considering using AC switches and such in a low voltage 12v or 24v system is the ‘amp rating’ of the particular item. Most AC lighting components are either rated 3A or 5A. Now here’s the thing: 3 amps at 240v AC power is equal to around 750 watts and that’s a lot of lighting power right there! However, the same 3 amps on a 24V DC system is just 72 watts, that is a tenth of the power. For 12V this drops to just to 1/20th or 36 watts, and one must remember these are maximums.

As we say, the good news is that DC lighting is more efficient than similar AC lighting and much better than using (converted) AC form an inverter. The second point is that using specialist DC lighting can give real life light outputs approaching 7 to 10 times higher than the equivalent AC incandescent lamps of old. For example using a 3W DC OnSolar led bulb will produce a close equivalent light output to a 25W old school incandescent. Therefore a quality multi element pendant ceiling fitting with say 5 lamp holders fitted with 12/24V OnSolar DC led bulbs will produce as much light as a 125W of combined incandescent power. In this case for example; 5 X 3W = just 15watts with 12V LED Bulbs and this would present a load to the wiring and switch of around 1.25 amps.

So, for lamp sockets; B22 and E27 for example, as long as we keep well within the ampacity rating we are fine. Typically one would not need more than three or four 3w or 5w led bulbs for a moderately sized living room environment. These lamps would be carefully positioned around the room to provide good illumination via a combination of Table lamps, Standard lamps and of course Ceiling or Wall mounted fittings.

For any other DC powered equipment we would advise fitting and using dedicated DC sockets of a high quality. This will allow for safe working of your 12v or 24v equipment. We do not advocate the use of ‘car style’ cigar socket / plug systems for all but the most basic systems as they are often not very well made, have or make poor electrical contact internally and can overheat especially in the case of multi-socket systems. Be aware that almost all of the car style / cigar socket type products are made for occasional use in a car environment.

IMPORTANT NOTICE:

OnSolar accepts no responsibility for damage or loss caused by any individual using faulty, incorrectly matched or rated electrical equipment. Please always consult an electrician with good knowledge of DC power systems for any advice before using any equipment of unknown ratings or origins.

Suitable fuse protection must be included in all circuits to provide a means of preventing overload. Be safe, be carful and considerate to yourself and others.

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