Probably the main thing I agonised over when considering the motorhome electrical system was whether to make the house system 12v or 24v. I read about other people's experiences, spoke to a few other motorhomers and of course everyone has their own opinion on what works best.
Decisions that you make impact on many other things - here's a few.
- What sort of a charging system(s)?
- Batteries - what type, how many and where will they go?
- What type of fridge - 2 way (electric only) or 3 way (gas operation)
- Solar panels?
- Generator?
- 240v
- Are we going to be doing a lot of free-camping (most definitely!)
12 volt or 24 volt?
Because the bus is 24v by default (and the alternator looks like it would power a small lighthouse) one school of thought is to keep the house system at 24v and use 24v appliances.OR Keep the house system at 24v and use a step down transformer to run 12v appliances.
OR Make the house system 12v and use a step down charger system to charge your batteries.
Which way did I go?
I know I took a long time to commit to a decision and I eventually decided on a 12v house system. In the time we have been tripping in the bus - 3 years and 40000 kilometres - absolutely no regrets!One good reason is that 12v appliances are generally more readily available and cheaper than 24v gear.
I believe my first major purchase was the DC-DC charging system I bought at one of the camping shows. It was an Australian made GSL 24v to 12v 60amp charger. It looked solidly built, I could speak to the people who made it, it was heaps cheaper than retail and (touch wood) I have had trouble free operation for the past three years. I had seen them advertised at over $500 (I paid about $350) and at the time these also came in 20 amp and 40 amp models. My philosophy in the whole electrical plan has been simple - make sure it is big enough to do the job (and a little bit more).
The GSL charger is a smart charger that hooks into the existing 24v batteries and because my charger was mounted about 3 metres from them I made sure the battery cable was big enough to to the job.
Without getting in to a lot of technical stuff about cable - you'll need to know that 4mm cable is not the same as 4mm2 (squared) cable. I visited the Springers store at nearby Lawnton who sold cable they had imprinted with the (squared) capacity. If you told them the distance you needed to run the cable and what your were using it for they had a computer program (just an excel sheet I think) that would calculate the size of the wire you would need (to allow for voltage drop). In most cases if it was close to capacity I went for the next size up. (Redundancy rulz! What is the point in paying $100 for a piece of cable, finding it inadequate and then having to pay another $120 for the next size - spend the extra $20 at purchase time and be sure).
A couple of other little bits of advice ...
- always allow a little bit extra length than you thought - it is amazing how a couple of little twists and turns add to the length required and it is no good if your cable run is 10cm short!
- Do yourself an electrical plan and try to work out what you want to run and where it will go. Buy a whole roll of wire and make all the runs before you fit out.
- I used 4mm twin for most of my average stuff like lights and 12v appliances.
- Because my build was a work in progress I didn't run all the wires I needed when I fitted out. This has resulted in added wiring afterwards - still possible.
- Recommend putting in some spare wiring for future possibilities - when I ran the wiring for my reversing camera I also ran a spare pair - and I have not used it!
- You are probably going to need a switchboard location - mine is in the overhead cupboard. Because my batteries are at floor level I ran a "main feed" or heavier wiring through one of the window pillars from top to bottom. I also used some relays at floor level so that I did not have to run heavy wiring to each switch individually. (might need to explain this better).
- Put fuses on everything (Make them easy to get to - I have a couple in awkward places that I regret) - Circuit breakers may well be the go now - they're about $10 now and I used them where I was running a "main feed"
Solar
AC charging
DC charging
Generator
Tips
Size of the wire - 4mm wire is not necessarily 4mm - learn about mm2.
Buy a big roll of wire, do an electrical plan and try to run all the cable you need before you fit out along with some spare capacity.
Reading and research indicates a lot of the problems people have with fridges and solar is the wiring used is simply not a heavy enough gauge.
Put fuses (or circuit breakers) on everything.
Using the bus as an earth?
Fridges
