Electrical System

The electrical system in an RV is a pretty complicated thing -- especially if you want to make sure you are as safe as you can be while maintaing as much power to do all of the things(tm).

Discounting the electrical system of the truck itself (which is entirely separate) there are two distinct electrical systems within an RV: a 12V DC system, and a 110V AC system you'd find in your house.

This is described in detail below, but here's the high-level picture of the entire system:

The 12V System

The 12V system is a pretty straightforward system in my build, there is an available on-board power supply (in my case, two 12V deep-cycle batteries that are rated at ~100ah each), things that use the power from those batteries and other things that put power back into those batteries.

Things that use 12V Power

For the most part, optimizing your RV setup to have as many useful things that consume 12V power DC is a good thing. For example, rather than installing a TV that runs on 110V (only so that TV can convert the power to some version of DC) is silly when you can just buy a 12V powered TV.

Here's a rough list of the things that consume 12V in the rig:

Core systems

A number of the "core" rig systems are powered off of 12V including:

• Water pump (to provide water from the pottable tank to the facuets)
• Exhaust vent on roof of RV
• RV House Lighting (my own custom LEDs)
• Water tank / compartment heater (prevent freezing)

Leisure Systems

Here's a rough list of the things that make the RV comfortable and fun to spend time in that are also powered off of 12V:

• TV
• Raspberry Pi Media Center (Kodi, and RetroPie)
• Cellular WiFi System

General-Purpose

In addition to these various systems, my rig has located throughout the space various "general purpose" DC power sources built in. These take the form of high-powered USB ports (2A), and very powerful (10-15A) 12V outlets using PowerPole connectors.

The USB plugs are obvious -- lots of stuff runs on USB. But the 12V PowerPole connectors are for powering generally digital devices that might otherwise be powered by a 110V->DC transformer. For example, my laptop. PowerPole-style connections are meant to handle very high amperages (45A even) and are often found in powerful radio systems.

Making adapters to supply the proper voltages for DC-based devices is pretty trivial, so I opted for this style of connector over the old and (IMO) stupid 12V "Cig lighter" plug you typically find in RVs.

In all, I plan on:

• 5 individual USB drops of at least 2 USB ports
• 6 individual PowerPole drops providing between 12 and 15A 12V DC

DC Safety Measures

Starting from the "actual" power source (the battery bank) we start with a massive fuse right off the batteries know as a catastrophe fuse. This fuse is absolutely never meant to blow, but provides a last-line of defense if the rest of the system decides to suck down way more power than it ever was intended to.

Past that fuse is a Battery Disconnect that cuts the batteries off from the entire system. This doesn't necessarily make the system "safe" (things that are supposed to charge the batteries can still hurt you), but it's the switch to at least cut the batteries off.

Looking at the circuit, you can divide the DC system into two parts: The "Internals" of the DC system where things like solar charges, 110V charger, and the Inverter live (which I in my mind sort of treat as the "internal" system), and then the feed that powers all of the useful / important stuff in the RV itself. For now I'm not going to talk about the "Internal" side and start from the "Operational" side

Operational DC Setup

From the Internal side I put a kill-all 200A Breaker, that can be used to basically turn off the entire functional part of the RV 12V system (or force it to turn off in case of a problem). This breaker feeds into a DC breaker panel divided into the following logical groups:

• Bedroom Area (20A)
• Living Area (40A)
• Bathroom (30A)
• Kitchen (40A)
• Water System (30A)
• General Purpose (20A)

When you add all that up, the maximum you should be able to pull without tripping a single breaker would be 180A, so the 200A breaker should be fine in front.

From each of these breakers there is a standard 40A switch to just turn that particular set of DC plugs on/off, and then from that switch the various things on that circuit are powered. The reason we have a second switch (instead of just a breaker) is because the type of breaker I am using here can't double as a switch (it just pops up if it blows and needs to be reste), so a separate switch is needed.

In the operational system (and internal, really), power is distributed using power bus bars for both the positive and the ground. These bus bars are installed as best as they can be in sane accessible locations and hidden behind access ports I intend on 3D printing.

"Internal" DC Setup

Before the 200A breaker that powers everything useful in the system is what I call the "Internal" DC system. This system is more the bones of the operation and includes things like:

• Solar Charger for pumping power into the batteries / system at large from the panels on the roof
• "Power Converter" that pumps power into the batteries / system from an external 110V source
• The 110V 1500W inverter that converts the 12V DC into general-purpose 110V AC power when not externally connected (more on that later)
• Battery / power monitoring

Each distinct component (i.e. solar charger, power converter, inverter) has a breaker sized appropriately attached as part of the system in case something goes wrong.

The AC system

The 110V AC system is the least straightforward part of my electrical system. This is due to the fact that in an RV the type of AC power you are dealing with, and the limits of that power, are many:

• 2-phase 110V/50A/50A shore service (the best of the best)
• 1-phase 110V/30A shore service (most common)
• 2-phase 110V/20A/30A generator service
• Inverter power (~110V/13A)
• 1-phase 110V/15A shore service (std household power)

In designing my rig's electrical system primary goal and assumption were as follows:

• Although there are 5 different options to powering the rig with 110V service, only one of them can be used at any time
• Regardless of which service was being used, it should be as useful and versitle as possible
• Obviously, it needs to be safe

With this in mind, I based my design around the best service I could (2 phase 50A/50A) and through a combination of other components and smart circuit breakout set it up to make it as flexible as possible.

2-phase 50A Service

Forgetting about the other options for a moment and just looking at the 110V 2-phase configuration, what I have is that feed first goes into an automatic transfer switch (that can switch between it, and shore power automatically), which then feeds two separate 110V/50A breaker setups. Each "major" electrical system / device is given it's own breaker (i.e. Fridge, Over, Stove, Washer, AC, etc) and then I have a single breaker for "General Purpose" devices which feeds into a separate sub-panel/group of breakers (more on that in a minute)

This will be set up as a Multi-Wire Branch Circuit in all cases, sharing a common ground with the "main" panel of breakers:

Multi-Wire Branch Circuit Wiring

1-phase 30A Service

When dealing with 1-phase 110V/30A service, I wire that single-phase service into one of the phases of the base 2-phase system and include a dedicated 30A breaker. Then, I use a special plug that goes into the 2-phase/50A system that shorts both phases together. This "jumper plug" then provides the same 110V/30A service to both sides normally powered by the 2-phase service.

Since that 30A service is fused at 30A (while the downstream panel is fused with two 50A breakers), we can still power the entire 110V system -- just at a lower total capacity (since doing more would trip the 30A breaker). In this way, my rig supports both 30A and 50A two-phase service in one electrical system.

1-phase 15A service

The 1-phase 15A service is basically just a pigtail feeding into the 30A service and is not intended to power the RV in any particularly useful way beyond possibly charging the batteries. An inline fuse in the power cable prevents me from drawing power power than these standard electrical cords can handle.

Inverter Service

The inverter is almost as useless as the 1-phase 15A service (extension cord), but the intent is when running off of battery power to provide a basic level of 110V service throughout the RV. Basically I want to let the 110v outlets throughout the RV work so someone could plug in their laptop, but not try to power the AC, Fridge, etc. from it.

With this in mind I broke off these general-purpose outlets into a subpanel that is fed from the main panel with a 15A "General" breaker. The magic comes in with the installation of a 110V 15A relay wired into the main breaker box.

What happens is this: When the main breaker box doesn't have power (no shore power at all, generator not running), the 110V relay is closed. When it's closed, it allows the general-purpose subpanel to be powered by the inverter. Then, when the main breaker panel gets power (because I plugged into shore power for example), it activates that 110V relay, disconnects the inverter from the general subpanel and connects it instead to the main breaker panel. This way the general purpose outlets always have power -- either from the inverter when off the grid or shore power when not.

Controlling the Inverter Remotely

I use a Cobra 1500W Inverter that has a RJ-45 jack that allows you to hook up a "remote control" to turn it on and off. Here is the pinout of that jack for future reference and potential IoT integration:

Pin 1 is the bottom most pin with the pin-side of the RJ-45 jack facing UP, Pin 6 is the top pin.

• Pin 1: Unused
• Pin 2: LED indicator
• Pin 3: Momentary Contact Normally Open Switch Pin
• Pin 4: LED indicator
• Pin 5: Momentary Contact Normally Open Switch Pin
• Pin 6: Unused

For the pins with the same description they are the +/- leads for that particular function. I.e. you short briefly 3 and 5 together to turn on/off the inverter which is indicated by the signal / LED on pins 2/4

Generator Service

The generator basically feeds directly into the main breaker panel in a similar way to the 30A 1-phase service. My generator is 2phase service, but they don't provide the same amps on both phases (20A and 30A) so I wired it in the way that makes the most sense for how things are used: The 30A service powers the circuits that have the fridge, general purpose, battery charging, and AC while the 20A service powers the cooking appliances (stovetop, oven). The generator has built-in breakers to make sure we don't overload it, and it shouldn't be a problem as long as we pay attention to what we use at the same time on generator power.

The generator automatically takes over for the rig through an automatic transfer switch that, when it senses the generator on and producing power cuts off anything coming from the shore. Likewise, the inverter automatically gets cut off when the main breaker panel is charged.