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I am trying to design electrical wiring for a small 1-bedroom house which will be only powered from solar panels. The minimum appliances in a house would be:

Appliances available in 12V DC:

  1. LED lights
  2. Ceiling fans
  3. Washing machine
  4. Refrigerator
  5. Air conditioner
  6. Mobile phone charger
  7. Water pump for overhead tank

Appliances not available in 12V DC (so far)

  1. LED TV
  2. Laptop/sesktop computer

Some of these appliances are available for DC solar power but not all. Also solar panels and battery combinations are of different voltages as 12V, 24V, 48V etc.

How should I do the wiring design?

Only DC wiring all over in the house while using small 220V inverters at the points where 220V AC appliance is to be connected OR do all the normal AC 220V wiring in the house while connect a big central inverter 220V AC at the point where I will put the batteries and solar panel wiring cabinet?

OR maybe mix of the two wiring?

Normally the DC wires have less resistance and size is 10mm copper wire while AC wire is 3/29 or 7/29 imperial guage wires mixed-copper (called china copper) used in my region.

The house will be outside city where there is no mains electric supply or grid.

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    \$\begingroup\$ In the first instance, refer to your local wiring regulations handbook \$\endgroup\$ – Andy aka Aug 24 at 12:23
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    \$\begingroup\$ There must a wiring regulation handbook but I am sure it would not have DC/Solar wiring related info in it. \$\endgroup\$ – scico111 Aug 24 at 12:28
  • \$\begingroup\$ Go off the grid and consider 220Vdc appliances with DCDC for low V non motor loads \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 24 at 12:31
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    \$\begingroup\$ Be a leader. Convert to DC motors , the world cant supply enough real copper in 10 yrs which is why the China copper \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 24 at 12:37
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    \$\begingroup\$ Too wide question to answer conclusively. I would go for one big inverter and then distribute 220 V AC. \$\endgroup\$ – winny Aug 24 at 12:53
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Your appliances fall into three categories:

  1. Washing machine, air conditioning

  2. Refrigerator

  3. Everything else.

Category 1 drives your requirements, especially A/C for a house.

Basically, you'll need both a fairly large inverter and a large battery bank to provide AC for these units. If you aren't willing to restrict your A/C and washing machine usage to daylight hours (which isn't that unreasonable for the A/C), you'll definitely need a large battery bank to provide the necessary power.

You can get a refrigerator powered by 24 VDC, which will draw about 25 amps for a full-sized unit. It is going to cycle on and off during the night, so you definitely need a decent-sized battery bank.

Once you've wired the house for these appliances, it will be most economical simply to extend the AC to the rest of the house and use standard power.

Lights, TVs and computers are commonly used at night, and often for long periods of time, so you'll need decent battery capacity. Furthermore, you'll have a hard time finding DC TVs and computers - even laptops, which operate from DC, normally don't operate on standard battery voltages, so you'll need some sort of custom converter if you go that route.

So overall, I don't see that dual wiring is that great an idea. It will cost you in the installation, and it won't save you anything much in operating costs.

Just go with a solar panel/battery/inverter system.

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  • \$\begingroup\$ you mean overall the wiring will be AC 220V wiring using a big inverter with the batter/solar panel? \$\endgroup\$ – scico111 Aug 24 at 13:14
  • \$\begingroup\$ You left "electric car charging station" off of your list. \$\endgroup\$ – besmirched Aug 24 at 14:31
  • \$\begingroup\$ Also, I think your estimate for the power consumed by the 'fridge is a bit on the high side. They aren't cheap, but you can get high-efficiency refrigerators and freezers these days that are marketed especially for off-grid applications: goedekers.com/UniqueOffGrid-UGP-470L1.html \$\endgroup\$ – besmirched Aug 24 at 14:36
  • \$\begingroup\$ @scico111 - As I stated in the answer, "Just go with a solar panel/battery/inverter system." You apparently live in a country with 220 as the normal line voltage, so I'd stick with that. \$\endgroup\$ – WhatRoughBeast Aug 25 at 12:59
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A main driver will be your most power-hungry appliances. Washing machines will likely require around 2 to 3kW. it won't be practical to run one from an extra low voltage supply, through a "small" inverter. You would be looking at substantial cables (perhaps 25mm² or more), and a large inverter with a surge rating above the rating plate of the washing machine, to allow for motor surges.

Do check the wiring rules where you live. Don't assume that extra low voltage DC supplies are excluded from them.

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If it were me, I’d retrofit the motors for 220Vdc

https://www.google.com/search?source=univ&tbm=isch&q=high+voltage+dc+motor.+220Vdc&client=firefox-b-m&sa=X&ved=2ahUKEwihpsK_77PrAhWQl3IEHdAbAfgQsAR6BAgKEAE&biw=1269&bih=927

Then down convert as required for control items with a 48V bus as a third wire to bus accessories and small appliances

This could be +/-110V + gnd for your application.

A BMS would need to be custom designed unless you can get some Tesla parts from a scrap yard.

Arc gap suppression insulation ratings must be higher.

However on retrospect, the latter may be costly so my final answer is create a 48V battery powered grid in the home and then stay in the LV limits for safety ratings, which was my concept of the future 30yrs ago. Then all 5V and 12V consumer goods could use DCDC converters without the low PF and have UPS to boot using cheap 10A Molex 4 pin (20A) connections keyed for polarity for <<1kW loads down to 1W USB.

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    \$\begingroup\$ If you dont like my answer be professional and say why or be that way \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 24 at 15:17

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