A/C Wiring

So…

There’s a lot on the internet, and one thing I knew wouldn’t be a problem seems to be a HUGE opinionated topic on all the forums and groups out there. How to wire your bus, or RV.

To debunk a few myths, it is true that if you plug your 50 amp RV into a “240V” outlet it would fry things, but what most fail to understand is no RV or home actually has 240 volts. Instead, you have two separate phases of 120 volts, when they come together at an appliance it will generate the 240. Nothing on your RV or Bus will require 240, but guess what?? it’s wired just like it’s ready to. I have a 50 amp 5th wheel that I plug right into my “240” dryer plug at home with zero issues.

The reason behind the two phases is now you can carry two runs of 50 amps to your RV, essentially, you will have 100 amps of 120 volts, A LOT OF POWER!

I put together a simple power-point generated drawing of the electrical system and will show you how it works, and what special components I bought to get it going.
Bus AC Electrical_001

Click here to get the PDF of this drawing Bus AC Electrical Tatum Skoolie

That is exactly how my bus is set up. the only thing I was not sure about and called an electrician for advice was the neutral and ground bonding. in a Home situation power coming off your transformer goes through a meter and to your main panel where they are tied together, but in a RV or Marine situation ground is tied at the Shore power supplier so bonding neutral to ground is not recommended on your RV, and if you do happen to do it, it has to occur at the first point of disconnect, in my case I would have done it at my first sub panel.

Here’s the break down if you need more details. My power comes into the bus via a 50 amp RV cord.50Cord

 

Here it is on Amazon

 

This cord plugs into a marine grade that twists and locks, and additionally has threads for keeping it secure

 

Inlet

 

Plug on Amazon

The plug I purchased was the cheapest one they made, we’re all on a budget, right?

 

As you can see it has 3 prongs and a grounding pin. that’s 4 wires, two of which are HOT with 120 volts each.

 

 

Power comes out of that plug and flows via a 6/3 wire (6/3 means there’s three wires at 6 gauge, and one bare wire for ground) to two 50 amp breakers at my first sub-panel. Out of these two breakers all the power from shore flows, it is the MAIN breaker for my setup, these sub-panels are very cheap, and so are the breakers for them, usually around $15-$25 for the panel and $3-$8 for the breakers. The hot wires connect to the input of the panel and then travel to my Manual transfer switch, additionally,

Aims 3k
AIMS 3k Pure Sine inverter/charger

I have another 40 amp breaker in this same sub-panel that feeds power to my inverter whenever it’s plugged into shore power. I did the wiring this way so no matter what, when I plug in, the inverter will charge my house batteries. Power passing through the inverter, or being made from the inverter also travels to my transfer switch.

Inverter at Invertersrus.com

The inverter is capable to transferring power automatically, but only at 40 amps of one phase, that’s more than enough for most people and especially if you’re only going to have one AC

4 0 Gauge wire
Temco 4/0 Gauge wire

unit. So this thing would be perfect for a 30 amp hookup because you wouldn’t have to touch
anything to transfer power. the inverter grabs its power from 6 6volt golf cart batteries wired in three sets of series to make 1 giant 12 volt battery, I used a Temco 4/0 gauge wire to make all my battery connections.

Amazon Link for Wire

Dang good wire!

400Abreaker

 

 

 

Of course don’t forget the breaker on such a large wire!

 

 

 

So at this point we have two different types of power able to feed the bus, but in order to harness all of it, we have to channel it through a transfer switch.Manual transfer switch

 

Transfer Switch on Amazon

 

This thing is massive, I like it. it’s fun to just play with.. but not after you set it up!

 

If you’ve looked at the diagram and followed along you’ll probably notice that the inverter only creates one line of 120 volts. that’s an issue when you get to the main panel, and what I did about it is at this switch. I crossed a cable from the hot side of the inverter wire to where the other hot side should be, thus providing 120 volts to both sides of the panel, but only at 25 amps. Sacrifices have to be made when running on inverter power, but this switch made it easy to get it right. on the output side of this switch it flows via the same 6/3 wire to the main breaker panel where all my breakers are installed. The trick to get the power distributed evenly is to line your breakers up in a manner that one AC unit is pulling from phase 1 and the other from phase 2. do your math, add it up and divide it evenly between the phases. if you pile all your heavy amp stuff on one phase, you’ll over load that 50 amps quickly and trip the breaker.

Needless to say, it all works just fine. I can prove it.

 

Billy

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2 thoughts on “A/C Wiring

  1. What main breaker did you use? Could you post a picture of its wiring? And does the inverter know when the batteries are full and stop charging? Also do you just screw a ground bar into the panel to separate the ground from the neutral?

    Like

    1. The main breaker is installed in the sub-panel below the main breaker panel, The shore power inlet wire goes directly into a double 50 amp breaker, then power flows through out of that panel through the lugs at the top and into the main panel. Yes the AIMS inverters all charge the batteries properly, once you select which type of batteries you are using. and Yes, I screwed a separate bar for grounding into the panel to separate from neutral. those are really cheap to find and any hardware store. I will scrounge up a picture…

      Liked by 1 person

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