Why is new stock, such as the GN class 717, not fitted with 2 power sockets per 2 seats?

[jellybaby]

Not really when you consider what it'd be used for. With LED lighting fed at 230VAC my lighting circuit runs at about 0.5A for the whole house if I recall rightly. Without lots of transformers this would run even lower, so if it had to be increased to run at say 12V it would still not be that high.

What's the voltage drop over your chosen conductor and length at 12V? I believe at 12V over a house it is significant unless you use much thicker conductors. The 12V for your lights is also not much use for USB without further conversion or would you have 3 voltages in your house?

How much does a single 12V power supply cost that is reasonably efficient over a range of currents powering 1 light (at 3 in the morning) and the whole house? What is the expected service life?

It might make sense if you have batteries locally but for a 100% grid fed property I'm not convinced. Having said that I look forward to hearing your experiences next time you have a rewire.

 

[aleggatta]

Not really when you consider what it'd be used for. With LED lighting fed at 230VAC my lighting circuit runs at about 0.5A for the whole house if I recall rightly. Without lots of transformers this would run even lower, so if it had to be increased to run at say 12V it would still not be that high.

Edit: just under 10A at 12V if I worked out correctly, again for the entire lighting circuit. It might require stepping up one cable size, but the cost step up is not significant when considering the cost of building a house. And a nice safety gain, too, as it'd be impossible to get a belt off it.

you also have to take into account the relatively high startup currents for LED lights, and the higher risk associated with DC switching with regard to contacts arc/welding together. Local LED drivers remove this risk (on a standard solar PV installation the isolators for the DC side will be triple pole, with the negative going through one pole and the positive running in series through two poles).

Using your calculated 10A at 12v, with an estimation of 30m of cabling from your distribution point to the furthest fittings, by my calculations (using this website) you would require a 25mm conductor for a 3.5% volt drop (recommended 4% max) for your lighting circuit...