Standard low voltage fittings?

[meaning]

Hi

We're really only in the beginning stages of our renovations in a ~50yo weatherboard, but it does involve replastering a number of rooms. I've begun ripping apart the first and would like to add extra power points (plus network connections for my computer-obsessed other half). Ideally one day we'll have some solar power happening too, and I'm wondering if sticking in some separate low-voltage wiring might be a good idea while we're in the middle of all this... Does anyone know if a standard for low voltage wiring (12 or 24 volts I'm guessing) exists yet? We can or could just put in some blank wall plates (and guess with the wire) until the time comes, but I was curious whether anyone had any experience with this...?

cheers
Meaning

[Bob Willson]

Low voltage wiring can use exactly the same wiring as ordinary 240 volt, so all you need to do is run extra off the existing circuits. However, if you want to do it cheaper and you are sure that you will only be using 12volts in the circuit then you could just run figure eight wire instead. Of course, if you are then stupid enough to go and run 240 volts through this wire then you could quite easily burn down the house. Good idea with the networking. I had to run about 15mm of my network outside the house on the back verandah. The dog found that little bit and chewed the lot up pulling about 10 metres of wiring out of the walls at the same time. Ah well, it is probably better going wireless anyway.
Actually, wireless is now a cheaper option than wired and it works great too, just ask Bitingmidge.

[meaning]

Sigh.. yeah, dogs are pretty good at finding these things. We currently have wires running everywhere and our "inside dogs" (temporarily I'm hoping) have meant a couple of phone cables in the last two weeks. I gave up on running my computer in the spare room off the network when they annihilated my beautifully resoldered cable. Apparently wireless is too slow for HWMBO (in matters of computing only, of course!).

With the low voltage wiring, I'd hoped there might be a standard, different socket type from 240V we could use and a maybe a convention for keeping it separate from the 240v system...

Cheers,
Meaning

[Dion N]

The Alternative Technology Association (who produce the ReNew magazine) are located at www.ata.org.au. They often have articles on solar and low voltage systems in the mag. The website has a bookshop and you might also find some info on low voltage systems there. Worth a look if you're considering going solar............

You could email the editor and webmaster, Lance Turner, who writes heaps of articles in the mag about various electrical projects.His address is on the website.

Cheers

Dion

[journeyman Mick]

Meaning,
with low voltage you get high losses. This means that the lower the voltage and/or the longer the run, the heavier gauge your cable needs to be if you want to have somewhere near the same voltage at the end of the run as at the battery. With timber stud walls you can drill through the top plate and nogging and leave a draw wire in the wall for future wiring. If you have masonry walls you will need to chase a groove into the wall and either fit the wiring now or put in conduit with a draw wire. Any telephone or data cabling needs to be in a seperate cavity to 240V (unless the phone/data is in conduit. I'd be fitting either cigarette lighter sockets or there are a few different 12V socket/plug systems available from marine chandlerys. Another thing to consider in light of the voltage loss issue is running 24V rather than 12V, but it depends on what you want to run and what's available. I want to fit some form of solar to our place (on the loooong list of things to do). I have already got a 12V pressure pump for our water supply (we're not on town water) and four large deep cycle batteries. Currently they have a battery charger with a seperate voltage regulator but I would like to add some solar panels. I'm probably going to run some 16mm2 cable (very heavy gauge) as a main feed because I scored 26M of it on a job a few years ago. I initially got it to run power down to my workshop but it wasn't long enough. I'll put some junction boxes up on the ceiling and run 2.5mm2 cable down the walls for lighting and power. I haven't decided on a socket/plug system yet but I guess whatever is economical and readily available. I'm leaning towards the plain old cigarette lighter socket as it means stuff will be compatible for going camping. There is a heavy duty plug/socket available that is compatible with cigarette lighters ("Sutars" brand, I think.) ReNew magazine is worth looking at for a whole heap of info on this subject and other resources saving ideas.

Mick

[echnidna]

Mick,
you can buy 32 volt globes that are physically identical to normal 240v globes but you usually have to hunt around for them. there used to be quite a few 32v household appliances too. So you could use heavy guage 240v standard wiring so if you ever get mains power its only a matter of replacing the outlets and not a total rewire.

[soundman]

there is a lot of stuff arround for low voltage stuff these days & its a real practicality now.

bear in mind the if you run 12V you need 20 times the current for an equavalent load. AND ther is a double whammy voltage drop in the wires works the same formular as 240 but you only have 12V to start with.

consider.
running bigg heavy wire (do the calculations don't asume)
you must provide good overlaod protection (12V wont kill you as easly but it can just as easly burn your house down)
consider running 24V or higher
consider running inverters & reticulating 240V (inverters are much cheaper than they were.
check out the new LED light sources comming on the market.

There are australian standards for all this stuff.

At this time you do not need to be licenced to run low voltage stuff but you do need to be carefull & know your stuff.

[vsquizz]

There are special low voltage DC domestic plugs available. They look similar to an AC plug but have only two pins in a T arrangement thus preventing inadvertent connection to mains power. You can use the normal 240 volt wire for these plugs as long as you follow the advice re-resistance in the threads above. However the standard wire will appear the same as the 240 stuff up in the ceiling so I suggest using different wire.

There is heaps of stuff happening with energy efficient homes and solar technology. Control by PC is a big thing. Some Geeks in Perth are developing a program for a solar house and using 115 volt (as in many parts of the world) battery banks and 24 volt systems (to open the windows, vents whatever)

I strongly recommend getting hold of the applicable Aust Standard. AS 1799.3 (Engineering) is one I have used (for pleasure boats) but the DC stuff is extremely relavent. Remember, you cant see electricity and its the amps that will kill you not the volts. If you exceed 48 volts you are into qualified electrician territory.

[journeyman Mick]

Bob,
a lot of remote farms and some mine sites ran on 32V. I've asked around as to why this voltage and the answer I got was that 32V and below couldn't kill you (sounds right, but it might be wrong). I have 240V, just no town water (not a problem, means my rates are lower and my water cleaner ) I have the battery backup for power outages (not uncommon, cyclones etc) and partly as I would like some renewable power. I'd be a bit worried using those low voltage "normal" bulbs as you migh get complacent and get a boot out of something you mistakenly thought was 12 or 24V. I've worked on older boats that had 24V bulbs that looked like standard globes, the skipper wanted me to just disconnect the wiring myself when I was doing refit work. I refused and made them get a sparky to do it as I didn't have a multimeter on me to test the voltage and they couldn't work out how to isolate the circuit. There was no way to prove it really was a 24V circuit and I certainly wasn't going to stake my life on their word that it was. Touching a live 240V circuit :eek: whilst working in a damp steel hull boat is not the way I want to go.

Mick (not the live wire of the party )

[GeoffS]

A couple of wrong comments above - 32 volts CAN kill, you just have to try harder! Probably shouldn't explain how to to do it on here but it involves a bath full of water and 2000% determination to commit suicide.
12 volts can start a fire EASIER than 240 volts. Because of the high currents involved fuses are slower to blow, thicker wire is more likely to get very hot before melting etc.
Advice - with the price of big inverters getting lower and the inverters efficiency getting better the idea of sticking to 240volts for all the appliances is getting very attractive and many people are doing it. I know of one person with a fridge and a freezer in his kitchen both running off solar power - he does have a large battery pack.
For lighting 12 volts can be fine particularly with the LED lamps that are now becoming readily available. Because of their very high efficiency the wiring doesn't even need to much heavier (or probably not heavier at all in a year or two). With the power and light circuits being totally independant there is little involved in a later conversion.
A comment on 12, 24 or 32 volt lighting - ordinary incandescant light bulbs (when you can find them) are very expensive, however because of their thicker filaments they can run hotter and tend to be a little more efficient but don't even think of them, there are many far more efficient alternatives available today.
For regulatary reasons in many states all ELV ('extra low voltage', 240volts is 'low voltage') must be done by a licensed electrician, however for insurance reasons it must all be done by a sparky.
Cheers

[jackiew]

I agree with the advice to contact the ATA ... the membership fee ( which includes subscription to the magazine ) can easily be recouped with discounts which are available to members on a whole range of good stuff which you will be buying for your energy efficient house.

have you thought about having solar power but being grid connected ... sell your surplus electricity back to the power company. Saves all the faffing about with low voltage and may be a better option if you're in town.

[echnidna]

There are currently some grants available to non profit organisations for grid connected solar electricity power systems.

[Bob Willson]

have you thought about having solar power but being grid connected ... sell your surplus electricity back to the power company.

Jackie, this is basically a scam by the various electricity companies. A friend of mine recently was hell bent on installing what SEQEB was pleased to call their environm,ental solar solutions pack. Thye system that he was interested in would have cost him about $10k. He was ecstatic because any excess power generated would be able to be sold back to Energex to help save the planet and defray the costs involved. I was pleased to be able to talk him out of this stupidity.
My reasons were:
If he sold the entire ouput of the solar panels to the grid he would still not be able to sell them enough to keep up with the payments on the system and it would all need replacing after a time and the whole process would start again.
If there was a power failure in the area then he too would lose his power. Eh????
The system would still not provide all his electricity needs.

[jackiew]

At the moment I don't think anyone installs grid connected electricity with the intention of making a profit. If you live somewhere where their is mains electricity then I suspect you are unlikely to be able to generate the amount of power required by the average household ( whether you are grid connected or have your own batteries ) as cheaply as the electricity company can do it over the short and medium term. As far as I understand it people who install these systems when mains power is available are doing it for other reasons. But if you're going to lay out for solar power then I can see the appeal in selling any surplus to the power company.

If a system isn't going to generate at least the electricity used averaged over the year then presumably the system is sized wrong?

You are quite right bob that if you've got grid connected solar if there is a power cut you get cut off too ... because you aren't charging batteries held on your property. On the other hand you haven't got to pay for the batteries in the first place or maintain them or replace them. I guess its all down to how often you get power cuts ( or how often you expect the power workers to go on strike ) whether you take this as an acceptable risk when compared to the cost of your own battery bank, additional wiring, purchase of more energy efficient products.

There is an argument that says if you have grid connected solar then you haven't got the same incentive to reduce your power usage as you would have if you were independent of the grid and could only use the batteries that you'd purchased. The incentive being that if you can reduce your power requirement then you don't have to buy as much battery capacity so the total cost of your system will be cheaper.

[Jack E]

Meaning,
As you are unsure of what you are going to do in the future I would definately go with the drawer wire option. If you run a good drawer wire with sufficiently sized holes throughout its run you should then have no problems pulling through whatever size cable you decide upon. There are some good ideas put forward here for you to look in to.
I disagree that if you have a grid feeding system that you will lose power if the grid loses power. If you set up a grid feed system and still use a battery bank then only feed to the grid when the batteries are charged you will be able to isolate yourself from the grid. With a current sensing relay you can then automatically switch off the grid feed in the event of a grid failure and happily have your lights on while your neighbors sit in the dark.

Jack (Licensed Sparky)