The Walden Effect: Farming, simple living, permaculture, and invention.

What can we fit in our electric box?

Empty breaker box

Our trailer came with some interesting wiring puzzles. First was this empty breaker box in the living room with absolutely nothing attached to it. Our best guess is that this was originally wired to an electric stove and furnace (both of which are absent, including their cords). Since the main breaker box (like this one) is only wired for 100 amp service, presumably the previous owners ran a second line in the trailer's original location and made the trailer 200 amps in a complicated way.

100 amp breaker box

So, the question became --- can we wire the new items we'll need into the main breaker box or do we need to follow the previous owners' lead? The first step was taking a good hard look at the breakers currently in use. On the right side, from top to bottom, there's a 15 amp breaker, a 20 amp breaker, a 15 amp breaker, a 20 amp breaker, then the main line coming in. Excepting the last, this side is clearly wired to the sockets in the walls throughout the house (based on the small amperages and the similarly small wires).

On the left side, only the bottom breaker(s) are in use. I say "breaker(s)" because this appears to be a 20 amp breaker with a 30 amp breaker in the middle, and I'm assuming the two are attached to the now absent dryer and hot water heater (respectively). Above that are two unused breakers.

What do we want to put back in? An electric range (40 or 50 amp breaker), a heat-pump water heater (30 amp breaker), a gas dryer (15 amp breaker...and a long story we'll tell you in another post), and a minisplit heat pump (15 amp breaker). Technically, these will all fit into the box, but will we be going over the amount of juice a 100-amp service can supply?

Electrical breakers

The internet suggests the rule of thumb is that the total amperage in your breaker box shouldn't exceed twice the total amperage of your service. So, a 100-amp breaker box can be wired with 200 amps worth of breakers. Adding up everything we have and want comes to 180 amps. So, unless I'm missing something, it looks like we're all set to wire in our new appliances!

(Sorry for the sparse, shoddy photos. It's a dark day and no electricity means we can't brighten it up much. We're hoping for juice by the end of the week!)

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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If it was me, I'd opt for a new 200 amp box. If you are using electircity for heat, a problem with the 100 amp box would be more than inconvenient. There is also the opportunity to increase use without having to upgrade to a 200 amp box, options will be available. Of course, that is assuming that the only added cost it the box, where we live service costs do not increase according to the size of the box, but are completely dependent on how much electricity is actually used. I am an ere on the side of caution person, who lived in the country with a 100 amp service and would not do it again.
Comment by Maggie Turner Tue Nov 7 08:29:23 2017

Hi Anna and Mark,

Electricity is simple. My first house had 60 amp. So I added a second panel with lots of breakers for electric heat, dryer, etc.

But for you maybe getting it turned on somehow would appear to be the real problem. I didn't have that problem.

i.e.- Large panel, few breakers. Then just add them and make it look more or less right.

You can always pay a 'real' electrician to come and bless what you have done.

One caution. Connections especially for large conductors may need to be retightened after a year or so since they 'relax' when under pressure.

Good luck. And get someone to show you how to be safe as you play. Left hand in back pocket, Put insulating tape on your tools if working near live wires. Always assume wires are live, etc.


Comment by John Tue Nov 7 10:47:24 2017
If you leave the 100 amp box in you will be at your limit right away,add a freezer and a fridge and a couple of space heaters and the breakers will start popping. If can swing it I would go a head and put a 200 amp box in.
Comment by Phillip Tue Nov 7 17:37:30 2017
In Australia, we put all our breakers on the bottom, in a horizontal line. It's funny seeing how it's done in different countries. The good thing about upgrading to a bigger box, are the options available to you later. We were able to have an electrical power-point installed in our box, saving us running chords from inside the house, whenever we wanted to use tools outside. And the power point is protected by the box, from the weather.
Comment by Chris in Oz Tue Nov 7 18:02:10 2017

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