AC or DC lighting circuits?

[Snakefoot]

Hi all,
I have just completed my solar system. Everything is working great so far. I have 2 DC circuits, one for fans and one for fridge. All receptacles and lighting are on AC circuits from the inverter. My question to you all is:

Should I use AC from my inverter for lighting or switch all lighting circuits to DC?

My inverter uses 5w when searching and 30w when under load. I usually only have 2-4 lights on at once, each drawing around 10w.

Would it be worth it to convert lighting circuits to DC or just a waste of time and copper?

Thanks!

[SunEagle]

Hi all,
I have just completed my solar system. Everything is working great so far. I have 2 DC circuits, one for fans and one for fridge. All receptacles and lighting are on AC circuits from the inverter. My question to you all is:

Should I use AC from my inverter for lighting or switch all lighting circuits to DC?

My inverter uses 5w when searching and 30w when under load. I usually only have 2-4 lights on at once, each drawing around 10w.

Would it be worth it to convert lighting circuits to DC or just a waste of time and copper?

Thanks!

As long as a DC load is low wattage (like a 10w light) then amps being drawn are low too so wire size may not necessarily be a cost adder. When you add up the number of DC loads (or lights) on the same circuit you will have to calculate both the total amps being used and the voltage drop to the last load. This is where a low voltage DC circuit can get expensive because it requires larger wiring.

Having a dedicated DC circuit for a single load (like the fan or fridge) is wise because it is easy to overload a low voltage DC circuit when you try to run too many things at the same time.

One thing you still need to do is make sure each DC circuit has a proper DC "over current" device (fuse or circuit breaker) which is sized to protect the wire.

[Sunking]

Draw this picture in your minds eye.

14 and 12 AWG copper wire is the most wildly used in house wiring connected to 15 and 20 amp circuit breakers respectively.

At 12 volts on 14 AWG wire with 15 amp breaker you can carry up to 140 watts maximum load to a 1-way wire distance of a whopping 9 feet @ 5% power loss.
At 12 volts on 12 AWG wire with 20 amp breaker you can carry up to 190 watts maximum load to a 1-way wire distance of a whopping 8 feet @ 5% power loss.

At 120 volts on 14 AWG wire with 15 amp breaker you can carry up to 1400 watts maximum load to a 1-way wire distance of a usable 90 feet @ 5% power loss.
At 120 volts on 12 AWG wire with 20 amp breaker you can carry up to 1900 watts maximum load to a 1-way wire distance of a usable 80 feet @ 5% power loss.

[donald]

One advantage of DC light circuits in smaller settings (cabin,RV, boat) is that the inverter is then normally off. Plus Edison would like your setup more.

Once you commit to AC lights it's likely the inverter will always be on.

[inetdog]

But if you want to be able to dim the lights, use of standard line voltage AC makes more equipment available. Not that dimming will automatically work well for all combinations of dimmer switches and CFL or LED lights.

[paulcheung]

AC fittings, fixtures and lights are much cheaper as it is widely available and the wires can run longer without much lost. so I would stick with the AC.