Monday, October 27, 2014

The first part of the egg! (wiring the inline 125V breaker)

We're really cooking with gas now.  No trailer yet, no, but lots of little bits and pieces that will soon make something pretty outstandingly cool.

What did I choose to start with?  Why, this fine gizmo, of course:

This thing was a bit of a struggle until I went to my local Tobram electrical shop and got some advice.  It's an inline 10A breaker for the 125V (house current) circuit.  This circuit will be 3 plugs in a line, the first being a GFCI.  The 12V circuit only interacts with the 125V through a battery keeper / trickle charger which will plug into one of the outlets.

Why use a breaker?  Aren't we covered by the breaker from the source and the GFCI?  As I discovered, no:
  1. GFCIs only measure a ground fault, ie: a difference in incoming and outgoing current, not the level of current itself.  It won't trip until the wires are actually smoking and shorting.
  2. The 125V wiring will be 12/2 Romex, which can handle 15A, and I will make sure the extension cord to the plug can deal with the same.  However, we could potentially be plugged into a circuit that is capable of a lot more ... a good example would be at an RV park, which commonly hands out 30A or 50A service.  So we need a breaker that can protect our circuitry.
All the big-box stores wanted to sell me a full household breaker panel.  Too big, too bulky, too expensive.  I knew this type of inline breaker must exist.  It just took a face-to-face with a knowledgeable electric store clerk to find it.  She only had 10A ones, but that'll be plenty for what we're plugging in.  If it's not, it's easy to swap for 15A.  The whole arrangement was less than $25 and fits in a standard 1-gang box.  Slick!

Here's the thing all closed up and neat looking.  It'll be screwed to the wall in the electrical raceway:

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