This bad person is a Red Earth Drop Bear system. We were originally going to use a German made B-Box unit for the battery storage but since then Australian made lithium iron batteries have come on the market in quantity. This system is a drop in with the batteries, charge controllers and inverters all housed in the cabinet pre-wired. More on this unit when it’s finally installed – another saga! Who’d have expected that hey?
In the meantime this part of the series is to share with you where we started our thinking and where we ended – hopefully our story might make your story a bit shorter.
Hey I’ve been wiring DC electrics all my life – I can do my house in DC!
This was me a few years ago. Just as a bit of background – skip over if you know the difference between AC and DC. DC (direct current), like the kind of current utilised in your car, flows between a positive and a negative pole in one direction only ( well actually the current exists in a quantum probability field on the outside of the wire and doesn’t ‘flow’ anywhere, but really who needs to hurt their head thinking about that!).
AC or alternating current switches back and forth the negative and positive poles 50 times a second so current flow is constantly inverting. DC puts a great deal of load on wiring for the same voltage compared to AC ,so much thicker wires need to be used for the same voltage or you need to use a much lower DC voltage. In Australia standard AC is 240 Volts and doesn’t require particularly thick wire, it will however kill you quite effectively. It’s actually pretty hard to kill yourself with DC voltage under 120 volts (but certainly not impossible!) and hence it is legal in Victoria for a non-electrician to work with what is termed extra low current or ELC i.e. anything DC under 120 volts. The downside is the voltage drop. Lower voltages mean greater voltage drop over distance. To combat this you need thicker gauge wire, a lot thicker. This can get very expensive very fast. The other issue is arcing – DC switches arc much more than AC and can easily weld themselves on (or worse ) at the higher DC voltages needed to minimise voltage drop. This means either using super clunky switches for everything or electro-mechanical relays or MOSFET solid state transistors with a heat sink. Again this gets expensive real quick.
Adding relays or MOSFETs means the wiring becomes anything but simple. So most things in your home actually run on DC these days and convert the AC current from the wall socket into DC to use in the fan or laptop etc. So why not just run DC in the first place? Because to avoid significant voltage drop you’re going to have to run 72 volts or more through your house (unless you want to buy cables that could hold up a bridge) and then step that voltage down to 12 volts or 14.4 volts or whatever each appliance needs at each appliance. Again this gets expensive and complex, to make a real, but relatively small efficiency gain. Modern appliances are getting so efficient the gain is negligible for the expense and complexity. Also, although you are able to work with ELC the Australian Standards for wiring with ELC in a house are quite onerous and you will need to comply with them. There are restrictions about what you can run next to what and the type of conduit you must use (steel) and this again becomes complex and expensive. If something goes wrong and there’s a fire or worse someone is injured you may find your insurance will not cover you and you also may find you are in some pretty serious legal strife if you can’t prove you met the standards. It’s simply not worth the effort and risk given the plummeting cost of solar panels and inverters.
But all the efficient stuff runs on DC anyway!
Yes there are some fantastically efficient DC appliances coming through, but there are some you just can’t get in a workable size. Washing machines, dishwashers, air conditioners to name a few (there are DC washing machines but they are tiny!). Everything for wiring in AC is a fraction of the price of that needed for DC. The wire itself is cheaper, circuit breakers are about one tenth the price and the list goes on. Yes you will have to pay an electrical contractor – perhaps try and find one that will let you do the rough in and supply your own components – this will save you considerable sums. We’ve been slowly buying up what we need for a couple years. Clearance items, auctions, eBay, FB Marketplace and even second hand if appropriate can save you a stack as it has us. Plus you won’t be forking out a lump sum to buy everything when you build because you’ll have already bought it all bit by bit. This can offset the cost of the electrician.
But I can do the panels myself right?
So onto the solar install itself – you can’t work above 120 volts, so that means you are going to have to hook up your panels in parallel rather than series (more on that in part 3) and this means you are also going to have to locate your inverter very close to your panels to avoid voltage drop (or back to the cables that could hold up a bridge). But the bigger kicker is you can’t legally wire more than 500 Watts of panels in Victoria. That’s basically two panels and you’re done. 500 Watts might run your caravan, it might even possibly run your tiny house if you were ingenious with your energy use or live somewhere really sunny all year, but it’s not going to power a full size house or even close. Remember you might think you can live with a pretty primitive environment but try it for a few years or do it when you’re 65 – you will not be so enthusiastic! Running out of power when you rely on it to pump water to drink or flush toilets can have some serious health implications – plus who needs the stress?
A final word
Now voltage drop isn’t so much of a problem in itself, although it means you are wasting your generated electricity. But, remember that high school science class – energy can neither be created nor destroyed? That electrical energy has to go somewhere and it goes into heat. Under specifying DC wiring can result in serious heating of wires – you can figure out why that’s a problem! We have enough issues living in a BAL29 zone without having to worry about our house killing us by fire instead. As stated earlier unless you’re in a van or a tiny house, DIY is not really an option in terms of cost, safety and legal compliance – I really hate to say it! But, if you don’t believe me, do all the laborious cost calculations and wiring designs as I did and the research into legal constraints and I guarantee you you’ll come to the same conclusions – only you’ll have wasted a couple of years of fudding around.
There isn’t really any other safe, durable and reliable way around it. You’ll need to budget a minimum of $35,000 for a good starting system that will last you several decades. If you are slashing the budget and using equipment with only a few years life span, then frankly you are effectively vandalising the environment and you shouldn’t be considering living off grid. We’ll have more information in part 3 on sizing and selecting batteries and other components and we’ll take you through our system in detail. Suffice to say though, we are spending the least we can to guarantee our grandchildren, when the day comes they arrive, will still have a reliable energy system to power what will be their life ship farm.