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My Solar 12v DC home lighting project


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Only thing I'm sort of wary when changing lighting to low voltage, is that when the house was wired they likely didn't foresee that. Usually the wiring is good for at least 10 amps, and if you go all-LED it's generally no problem (roughly 0.5a per lamp). Also, there's no way that will pass an electrical inspection at present :-)

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Only thing I'm sort of wary when changing lighting to low voltage, is that when the house was wired they likely didn't foresee that. Usually the wiring is good for at least 10 amps, and if you go all-LED it's generally no problem (roughly 0.5a per lamp). Also, there's no way that will pass an electrical inspection at present :-)

 Presto. We changed all the lighting and redid all the wiring in the house so that we didn't use any of the existing wiring for this very reason.

 

I have a list of about 20 things that have to be done to pass inspection. The big one is actually in the roof where I have to run all the new wiring in its own conduit and clearly marked as being 12v DC. I've done most of it, but left sections where the new additions have to go in first. The DB board also needs to be changed which I will do as soon as my circuit breakers arrive. The list is long, but not impossible. to meet. 

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  • 2 weeks later...

Few things worth mentioning.

 

1) SANS requires a CoC for this installation. (which can affect if your insurance will pay out)

2) SANS requires that 12v DC and AC not run in the same conduit. In fact nothing but your AC power may run in the AC conduit.

3) SANS require no more than a 5% voltage drop from source to supply (which is the main reason 12v DC is a massive pain in the behind).

 

2 is due to the possibility of a electrocution hazard of mixing an very low voltage with low voltage (low voltage = 220v in SANS) installation. You don't expect to get electrocuted by 12v but it can happen if the wires run in the same conduits in a fault situation.

 

3 is due to fire hazard. More than 5% voltage drop indicates a fairly large amount of heating in the wires.

 

SANS is mostly about safety against electrocution and fire.

Low voltage DC is pretty safe in terms of electrocution but fire hazard is somewhat higher due to the large currents involved.

 

Either way, looks like you put a lot of thought and work into it!

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Wiring in the same conduit example: Apparently this caused some explosions in planes. They too had the requirement that high voltage should never go anywhere near the fuel tanks. They did have low voltage signal wires though... and those ran close to other high voltage wiring, and as these got older those wire shorted out, high voltage into the fuel tanks... kaboom ;-)

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I sat with the same conundrum a while ago and decided to just use 220V LED lights instead of 12V. A watt is a watt, right. So 12v, 5W should (in theory at least) use the same energy as a 22V 5W LED light - although the small driver circuit in the 220V globes do consume a bit of power as well. So the 220V globes do use a (slight) bit more power than the 12V globes would. At the end of the day I could still use the same conduit, same wiring, same switches and same switch board. But I have an inverter to invert the 48V DC to 220V AC. 

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I still have to put a 220V LED lamp on the scope to check it out. With the 12V downlights I can tell you that driving them from 220V is significantly less efficient than using DC, because they have an absolutely horrible power factor. To understand this you must know the difference between watt and VA... so basically, when running from Eskom it really makes no difference as they bill me for Ws and not for VAs, but when running from the inverter, it does matter that a 5W lamp is closer to 20VA :-) Now I don't even have my lights on the inverter yet. Planned for some future time. We prefer using bedside lamps and floor lamps anyway, so right now backing up one plug-circuit in the house does the job perfectly.

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Just remember Plonkie that the batteries only supply the real power draw by the load and not the apparent power.

 

The inverter still however has to be able to handle the larger current associated with the apparent power draw.

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I did same, tried the 12v route but once I got the numbers itv re-wiring, limits ito lengths for 12v - re-using existing 220v curcuits turned out much more attractive - even more so that you can switch back to Eskom.  :D

 

Just need to ensure the lights are as efficient as they can be.

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