load shedding free lights

[adrianh]

If you power supply (solar panels) is just on your roof then you don’t need to transmit power over long distances. The problem with DC is that no one is making appliances for them and there is no standardizing on a voltage a voltage of around 120v would be nice. All the products that’s made for DC revolves around vehicles, caravans, and boats all things that’s either 12 or 24 volts. Although this DC market is very small its technology has come very far the products that are available are very power efficient. You can buy 100 -150 liter fridge/ freezers that consume only 3 amps. (Google China DC fridges) Look at vehicles and you will see that they don’t use heavy wiring for things like motors as they are very power efficient. I have to disagree on switches even DC high amperage ones are no bigger than the ones used for AC go to any car electrical shop and ask them to look at their range of switches or look at a car relay that’s up to 40 amp and its contacts is no bigger than that of a 220V AC one. Adrian, give me your mail address and I will send you the globe specs.

Adrian_hill@mweb.co.za

[AndyD]

The problem with switching DC on and off with an isolator swtch, or any switch for that matter, is the arcing.

When you switch AC the waveform is crossing the zero line 100 times each second, at that zero crossing point no current is flowing in the circuit (excluding PF and harmonics etc) so any arc that occurs at the switch contacts extinguishes itself.

With DC there's no time that the waveform crosses the zero line, the current is constant so switching arcs don't self extinguish which means switch contacts suffer enormous wear and tear with DC.

You do get switches that are rated for AC and DC usage but you'll always find they're derated for DC use. For example a 60Amp AC isolator might be rated for 20 or 30Amps DC use as well.

[gombault]

Car starter solenoids contacts switch very high loads between 300 and 600 amps the contacts are around 8mm, starter solenoid can switch many times per day and they last for many years. I don’t know how dangerous a 120/110V DC system will be I just know it’s very popular, all underground battery locos today are running on 110V DC system. One could reduce the voltage to a safe operating voltage. The question is how many high power appliances do you really have in a house if you exclude the geyser and stove?

[Justloadit]

Washing machine, dryer, kettle, microwave, vacuum cleaner, wife's hair dryer and curler, steam iron, slow cooker, steamer, espresso coffee machine, swimming pool pump, lawn mower, weed eater, 230V electric gate, .......but a few I can think off hand.

[Dave A]

Dishwasher, tumble drier...

[gombault]

Things like lawn mowers that use induction motors won’t work on DC. We don’t have all these households appliances made for DC at this stage. I have been on a yacht some time back and it had many appliances that was DC powered I think they do make many DC products for things like boats but they are expensive because it’s a small market. I don’t think an inverter system is the way to go because of the high consumption on the batteries. A pure DC higher safe voltage system will be a far cheaper option for the future. For now we do have lights that work perfectly from low voltage DC I spoke to someone yesterday that’s converting fridge/ freezers to work of DC. It might take time but DC is coming.