The Rustic Electrical Setup

The electrical work on a Tiny build is something that a lot of people have the most fear over. I had no fear, so I thought I’d detail my electrical build in the hopes that it would help some folks. 

I am NOT an electrician, so standard DIY “Don’t blame me!” rules apply here. :D

In general you can stick to some basic rules and you’ll be fine. Those rules are:

• Use NMB/2 cable inside your Tiny. (It has three wires, neutral, hot, and ground. They don’t count the ground.)
• Use 12g wire for outlets.
• Use 14g wire for lights only. 
• Use a GFCI outlet as the first outlet for the bathroom and kitchen circuits. 
• Don’t put an outlet within 3’ of a tub or shower, or right over a sink. 
• Wire outlets  so the center of the outlet is between 12-18” from the floor. A hammer’s length usually does the trick. 
• All wiring connections must be done inside a box. 
• Try to keep less than 3 connections inside a box. It gets hard to fit everything back in with too many connections. 
• Don’t connect too small of wire to a too large capacity breaker. 16g wire on a 20A breaker is BAD. See the little table below.
• Outlets have amperage ratings. Don’t put 15A outlets on a 20A circuit. 
• Wire needs to be secured by a staple within 6” of a box. Secure wire every 4’ it runs along a stud/joist, and within 12" of an end or turn.
• Use metal protective plates to protect the cable where it runs through the studs. 
• Use appropriately sized twist on wire connectors to connect your junctions. I just bought the Big ones and used them for everything so there was no question. There's a little legend on the box that explains it well. 

Ok, on to my setup. 

I planned for only 120V service to my house and throughout my house. 

I used a marine grade RV electrical inlet on the outside of my house. 

I used 10g wire to run the connection from the outlet to a 2 breaker panel inside the house. I actually think I should have used 8g wire here, as this wire needs to be able to carry current for the whole house. On the other hand, most Tiny Houses have 30A or less service, so it’s probably fine anyway. See the table below. 

I used two circuit breakers, a 15A for the “dry” side of my house (living room and loft) and a 20A for the “wet” side of my house. 

It’s generally recommended to have higher amperage in kitchens because appliances take a bit of power. I was also running my 120V 4.5 gal hot water heater off that circuit. 

From there, I ran 12 gauge wire throughout the house. In general it’s safe to use 12g wire on 20A circuits and 14g wire on 15A circuits. I just ran 12g through the whole thing… Which was mildly terrible, thicker wire is a pain to work with. 

I ran my wire at hip height in the wall, because it was convenient to use my hip to push the drill through the studs. :D As far as I know there’s no specific height requirement. 

The first outlet on the 20A circuit was a GFCI outlet. All the “downstream” outlets were attached to the “load” terminals of the GFCI outlet. 

The living room and loft areas were on the 15A circuit and there were only two minor complications. 

The first was running the wire over the door. I left enough room above the door in my framing plan, so that went smoothly. 

The second was that I wanted to control the main light from two switches, one by the door and one up in the loft… I didn’t want to climb my ladder in the dark.

For that I simply wired a two way switch using NMB/3 14g wire. There are many online tutorials to explain a two way switch, so I won't do it here.  :D  This required a lot of junctions and was a Pain to squeeze everything back in the box.

That was really it.




When planning your house, look at your large appliances and see how much power you’re going to pull. The basic formula you’ll need is Power(in Watts, W) = Voltage (120V usually) * Current (in Amps, A). 

For example, I had a heater at 1500W, and my electric water heater at 1500W. That’s 3000W, which will pull 25A. If I plugged this into a 15A regular outside house outlet on a regular house… I’m going to pop the breaker inside the house whenever I’m running my heater full bore on a cold day and I try to take a shower… But if I’m plugged into a 30A service (All of our Tiny Houses are on 30A here at SHC for just this reason.) I’ll be fine. I probably also shouldn’t plug my heater into the “wet” side of my house as 12g wire is really only rated for 20A. 

​
Wire size    Amperage    Recommended Power load (not max)
10g                30                      2880
12g                20                      1920
14g               15                       1440


Don't kill yourself! :D

​Tony