24V Wiring Throughout Interior

[Chram]

Hey There!

We are running our system at 24v. 6 320w panels coming down to 200-400ah lithium batteries (400-800 at 12v).
Multiplus 3000, charge controller, battery monitor are all victron. We will have a DC to DC converter for the 12v max fan, at a minimum.
35’ bus with heavy loads. Many will need to be at 120, so I’m trying to take as much as I can off the inverter.

How much more efficient would 24v lighting be than 12v?
Can you have 3 systems running(12,24,120), and is it worth it?
What gauge wire is typically used for 12 and 24v runs? Wondering how much lighter I can get with 24v.
Any ideas for other loads that can run on low voltage?
Any tips tricks and advise would be very much appreciated!
We’re in the last bit of planning stage where all advise is helpful advise.

[TheHubbardBus]

If it were me I'd run the numbers, but I can't imagine there's any significant efficiency benefit to running 24v vs 12v lighting in the limited space of even a large bus. I'm sure you're running leds and as such, the lighting draw is likely one of the smallest loads you'll see. I doubt it would add up to anything consequential, but I could be wrong.

That being said, 24V lighting for a 24V bank makes sense. At least you'd have lights if your step-down failed. So that's one potential benefit.

No need for 24V specific lighting if you decide to go this route. Just run each pair of 12Vs in series. Definitely easier to find/replace if a unit fails. Unless you have an animosity towards even numbers.

Wire gauge is dependent on any number of factors. That's another discussion entirely. But I really don't think you'd save much, if anything, going w/ a smaller gauge allowed by 24V lighting. It would likely be the only thing using that size wire, which means you wouldn't likely get the price break you would buying more of a larger gauge at quantity. Blue Sea actually recommends using nothing smaller than 18awg even for loads that can get by with less, citing the physical strength of the wire as a factor worth consideration.

[Iceni John]

Compared to the total cost of a bus conversion, the cost difference between 12V and 24V wire/cable is utterly inconsequential. It's just noise! There are plenty more things that determine the overall cost of a conversion, and wire size really isn't one of them.

People think that a slightly higher DC voltage will somehow work better. Maybe it does in a house with a very large (multi-kW) PV installation a great distance from its inverters/batteries/etc, but with the comparatively small PV installations on vehicles and their very compact size any theoretical benefit is just that, theoretical. I prefer to keep things simple and have as few different voltages in a vehicle as possible: folk with MCIs and similar buses run into this with their original 12V and 24V chassis system. KISS!

John

[Rwnielsen]

Just for the sake of argument, I'm running a 24 volt system. DC voltage doesn't travel well and suffers significant drop over distance. My electrical "system" is behind the driver's seat (40' bus). I'm running 3 pairs, #6 wires, each fused at 60 amps, the back left corner, the center right side and to the kitchen area (center left), to small fuse blocks. In the rear I have a 240 watt, 24-12 volt step down transformer for the water pump and 2kW diesel heater. I also have a small 24-110v inverter for the water heater and a small(ish) 12 volt TV and a couple lights. Center right side are 2, 240 watt step downs...one for the 12 volt Norcold (dedicated) and the others for a 5kW diesel heater and a few lights. Center left is Whynter chest freezer (65 qts) and small misc.
The reason I'm going with 24 is the physical size of the wire, not the cost. I want to maintain consistent voltage over distance and its.far easier to run, support and protect a pair of #6 than #2. The overall majority of the system remains 12 volts.

[magnakansas]

Where I think 24volt or 48 volt has an advantage over 12volt….. high amperage loads, inverter to batteries, solar panels to batteries. Batteries to electric motors, like starter motors, fan motors, the sized of those big beefy cables can be much smaller.

All of my exterior lights in led - not counting headlights don’t even add up to 10 amps. All my interior lights don’t add up enough to even need 12 ga wire…..just not a big issue. I am using 10 ga for the 12v refrigerator but that is even overkill.

The only reason I stuck with 12volts is simplicity. Cooling fans , lights, radios, amplifier, USB ports, the little air compressor to blow up air mattresses and toys, all this stuff is super easy to find in 12volt. I have massive battery cables for my inverter…. I will eventually have a 3000 watt sine wave inverter. I have an 1800 watt now. I have this bus sized 200 amp alternator- thanks Cadillac- he recommended it.

If you end up with big solar and big storage I think the 24 or 48 would be a to go. For me 12 volts makes it easy to cross connect batteries, alternators, chargers, and all the other stuff on the bus.

William