Thursday, August 24, 2017

RV Electrical Basics

Because my RV is basically a mobile Bug-out location (BOL), I need to make sure that the electrical systems are good enough for moderate use. I'm not going to be living in it full-time for years, so it doesn't need a generator capable of providing substantial power for decades nor the fuel capacity to keep a generator going that long, but I do want to be able to have lights and running water (I could live without the microwave). Here's what it has and what I'm going to do to improve it.

What's There?
Like most motor homes, mine has three separate electrical systems and they're all interconnected to a certain extent. The main separation is between the engine electrical (known as the “cab”) and the living quarters (the “coach”).

Cab power is 12VDC, provided by the engine's starting battery and alternator.
  • The alternator is a heavy-duty version of what is normally found in cars, rated for about twice as many amps as a car alternator. 
  • The battery is a large light truck battery.
  • Cab power runs all of the things associated with driving the motor home like headlights, turn signals, clearance (marker) lights, engine electronics, and the starter. 
  • In order to prevent idiots from getting themselves stranded with a dead starting battery, there is no way to get power from the cab to the coach.

Coach power in my RV is a mix of 12VDC (batteries) and 120VAC (electrical hook-ups).
  • There is a storage compartment at the rear of the RV for two deep cycle batteries, like you'd use for a golf cart or trolling motor. 
  • These supply all of the lights on the ceiling as well as the water pump, furnace (it has its own miniature propane furnace for winter travels), control circuitry for the refrigerator and water heater, the starter for the on-board generator, and various little fans and exterior lights. 
  • These batteries are kept charged by a converter box that uses 120VAC from either the generator or shore power (when you're plugged into an outlet at a campground). 
  • There is a “starter boost” switch on the dashboard that will engage a solenoid and briefly add the coach batteries to the cab battery in case you left the headlights on and can't start the engine. 
  • I've already switched out all of the 12VDC incandescent bulbs in the coach with cheap LEDs from Amazon. I picked two different styles of LEDs to do a comparison (short ones and long ones), and so far there is very little difference. I can have all 24 lights on at once and only use as much power as 2 of the original bulbs, and they run cooler. The shift in color from the yellowish hue of the incandescent bulbs to the slightly blue of LEDs also makes the RV look more appealing -- it just doesn't look as old and worn under bluer light. Morale is important, especially if I plan on spending a lot of time in the RV.
  • The 120VAC system is fed by either the generator that produces ~50 Amps, or the shore power cord which is rated for 30 Amps. 
  • The rooftop AC units are 120VAC only and each pulls about 20 Amps, so there is some creative use of switches and wiring to power both of them at the same time, but that's particular to my RV. 
  • The refrigerator is a 3-way model, running on 120VAC, propane, or 12VDC. 
  • There are a handful of standard household outlets scattered around the coach so you can plug in your laptop, coffee maker, power tools, or cell phone charger. The one in the bathroom is actually a GFCI (Ground Fault Circuit Interrupter) model because there is a possibility of it getting wet from the shower. GFCIs react quicker than standard circuit breakers and provide an extra level of safety in wet locations. 
  • There are also duplex outlets on the outside of the coach for hooking up anything you want to use outside, and they have rain-proof covers on them.

What's Missing?
I have plans to modify the electrical system quite a bit. There is some redundancy in the existing setup, but I want more; I'm a belt and suspenders type when it comes to simple systems that I plan to use a lot. I don't want to be shut down on the side of the road because of a single fuse (BTDT) or have to cancel plans because of a minor mechanical issue. I like redundancy, it's insurance against Murphy's Law.
  • The current coach battery setup is too small. There is currently room for about 200 Amp-hours worth of battery and I'm going to double that at least. I'm investigating where would be best to place at least two more deep-cycle batteries.
  • The power converter is 120VAC to 12VDC. I'm going to be adding a large inverter to be able to go the other direction and use the new coach batteries to provide limited 120VAC. The inverter will probably be placed in a space vacated by the old water heater after I replace it with a more efficient on-demand model.
  • There will be solar panels on the roof, tied into the 12VDC coach batteries. Mounting them and running power cables is under study right now; it'll be next spring before I'll be able to afford them, so I have time to plan out how many I need and how I want to mount them. I'm trying to figure out what I'll need and how much space I have to mount them on. You also have to remember that they have to stay in place as I'm traveling down the road at 65 mph, so mounting is important.
  • Most of the interior 120VAC outlets are going to be replaced with modern versions that have USB 2.0 power ports built into them. Too much of our lives runs on rechargeable batteries these days.
  • The outside outlets and the ones in the kitchen area are going to be replaced with GFCI outlets. I like having the extra security/safety, and they're not that expensive.
  • I am going to install a master kill switch on the cab battery. It will be hidden from sight, and will completely disconnect the battery from the engine for anti-theft and anti-idiot reasons. I'm trying to decide if I want to use a keyed switch for extra security, but run the risk of losing the key and being shut down.
  • All of the outside lights, with the exception of the headlights, need to be switched to LEDs. LED headlights exist, but they don't work well in cold climates. The heat from a halogen bulb will melt ice and snow off of your headlights, but LEDs run cooler and get blinded fast in any kind of winter weather.
  • I need to install LED light bars/strings inside the cabinets and put a few along the floor as night lights.
  • Each of the exterior storage compartments is going to have an LED light installed inside, along with a switch on the door. I am contemplating wiring the switches to a notification panel in the cab so I'll know if any of the doors are open before I start driving.
  • I need to install a separate AM/FM radio for the coach. We like music, and I don't want to use the cab battery for anything once we're parked. One nice thing about having a smaller space than a house is that I won't need very large speakers to fill it with sound.
  • Speaking of radios, I am working on a communications station for shortwave and other radios. I'll have a Citizen's Band (CB) up front by the driver's seat, but I want a scanner and a Ham Radio setup as well. I'm still working on getting my Ham license; testing locations are a bit of a drive and they don't test very often.
  • The generator is not currently hooked up to either the 120VAC or the 12VDC coach system. I'm not sure if this is because the previous owner (PO) couldn't get it to run or if he just didn't want to mess with it. I will be dropping the generator out of its hiding place and doing a thorough tune-up/minor overhaul on it, which will be covered in a post of its own. 
  • The PO has passed away, so I can't ask him questions. I'm finding a lot of electrical issues, so he might not have been able to offer much help anyway. He also didn't leave any of the owner's manuals in the RV, so I'm digging through various internet forums to find what I can.

As I've mentioned before, I bought this RV cheap with the full knowledge that it was going to take a lot of work to get it back into shape. Besides learning the details of how things operate, this work will allow me to customize the RV to fit my personal tastes. So far, I haven't run into anything that I can't do, and if I do find something out of my reach, I have friends who can work on things for me. My worst case scenario would be something major wrong with the engine, but I can get that swapped out in a buddy's shop within a week, although it might cost me a case of beer and $1000 for an engine. Ford made a lot of the 7.5L (460 cubic inch) motors and they're easy to find.

I will soon have access to a paint shop that is large enough to fit the RV, so it may even get a fresh coat of paint this winter. Being a generalist has its advantages, and I've learned how to do a lot of different things over the years.

Next week I'll cover the plumbing, which is almost as complicated as the electrical system.

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