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Re: Would ELV branch circuits be a good idea? [Re: LongRunner] #218191 02/07/17 06:55 AM
Joined: Jul 2005
Posts: 223
aussie240 Offline
I thought I might get motivated and reply to this seeing as I have had 12V power and light circuits in my house since 2005. They're fed from solar charged batteries (400Ah)and are independent of the mains supply.
Having collected numerous 12V appliances and light bulbs over the years, it was the obvious voltage to go for. Now, my experience looking at many 12V installations in other houses, caravans, boats, etc, is most are poorly done with the resultant dim lights and inability to run any decent size loads off them.
First thing I decided to do was run ring main circuits for both light and power, thus doubling the conductor area and reducing the voltage drop problems for "the last socket on the circuit".
Next thing was to calculate the wire size; I allowed for one volt drop at the last socket with a 10A load. Any properly designed 12V load should work OK on 11V. Also keep in mind when the sun is shining there's a bit more voltage. 16mm cable sufficed quite nicely. This is run around under the house with the socket connections tapped off with short 4mm cables. The sockets are the ELV T sockets (another American socket adopted in Australia), with negative, which is earthed, at the bottom pin. Cigarette lighter connectors are unreliable and can't handle much current. I wouldn't use them in a serious installation. A 15A CB protects the circuit.
For the light circuit, given the loading isn't quite as high, I installed a ring main in the roof using 4mm wire. It feeds E26 sockets with pull chain switches. Turning the light on in one room barely dims the light in another. The bulbs are 50W incandescent. The CB is also 15A. The main CB for the batteries is 80A. There are similar light and power circuits in my garage running off the same batteries, and another independent set up in the shed at the other end of the backyard. I use quite a few B22 base 12V incandescent bulbs too. The all night outdoor lighting is LED only to conserve battery power. I've modified 240V PIR and time switches to work on 12V. The PIR switches are used with incandescent lamps as they're not on for very long. Besides, a LED or CFL is totally out of place in an antique street light.
As to the performance, it works as it should and I'm very pleased with it. Virtually all my low voltage loads run off this system. Things which draw power all the time like clocks (LED and Nixie tube), telephone answering machine, Numerous valve radios, mostly home made also run off it, various battery chargers, etc. In fact I haven't got one plugpack actually in use. I also have various inverters powering 240V and 120V appliances.
However, the batteries have come to the end of their life - the present ones are just on 10 years old, so it's time to fork out a few hundred dollars. Even so, I wouldn't be without my 12V circuits.

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Re: Would ELV branch circuits be a good idea? [Re: aussie240] #218192 02/07/17 07:42 AM
Joined: May 2015
Posts: 68
LongRunner Offline OP
The article said the tap-offs to the individual sockets were 2.5mm2, though... Nice set-up, anyway. I also enjoyed your article about making resistive line cords from electric blanket elements, which made me think that they could be considered (relatively) safe even by modern standards with present-day materials (silicone insulation?) - and reliable too, with the finely stranded wire. (Even though modern electronics wouldn't have much use for them...)

Re: Would ELV branch circuits be a good idea? [Re: LongRunner] #218206 02/09/17 05:31 AM
Joined: Jul 2005
Posts: 223
aussie240 Offline
Yes, your're right re the 2.5mm tap offs for some of the sockets. It was done over 10 years ago with old 2.5mm that looks the same as new 4mm, and my memory missed that. However, later sockets have used real 4mm. In any case, the distance between tap off and socket is less than 1m so not really important either way. I must update the article as it's equally as old and a few things have changed.
The line cord resistors work well; I have two in use so far. It surprises me the American vintage radio enthusiasts never thought of it, but I suspect the AU/NZ type of electric blanket is unknown there with everything being centrally heated.

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