4 Comments to “She Blinded Me With Science or How do I Wire my Earthship?”

  1. Jeremiah Morrison

    Jun 27th, 2010

    Good morning,
    My father and I got a chance to visit you last year while you where still filling tires on the U’s. I am very interested in your electrical system. I pulled my code book out and in the CEC it doesn’t matter if it is AC or DC the wire must be sized for the load. Wire size decides breaker size. I do suggest larger appliances that have known loads be on there own circuit as it makes servicing much easier and safer.
    If you have any questions I can help with please send them my way as I would love to start picking peoples brains at work. Do post your prints or sketches when you get a chance I would love to see them.

    Good luck
    Jeremiah

  2. Chris

    Jun 28th, 2010

    it doesn’t matter if it is AC or DC the wire must be sized for the load

    Yes … this is my understanding as well.

    Wire size decides breaker size

    I have not read enough on Class II circuits but I believe you are allowed much lighter breakers for comparable wire sizes.

    I will try to post my work on the electrical as I proceed.

    Any comments are welcome!

  3. Seth

    Aug 5th, 2011

    A great resource for planning out you DC electrical system is to look at the boat industry. There are tons of resources available out there.

    DC wiring principles are well established in boats, RVs and yachts. Fire (including electrical fire) is one of the leading causes of loss of life and property at sea so the industry takes safety and efficiency quite seriously. Check out this primer from a major boat equipment supplier:

    http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&catalogId=10001&page=Marine-Wire

    For folks just running a couple of LED lighting circuits, that’s probably enough to get you in business.

    For folks planning on trying to go totally off the grid or just doing as much DC as possible, I highly recommend Charlie Wing’s book “Boatowner’s Illustrated Electrical Handbook” and Nigel Calder’s book “Boatowner’s Mechanical and Electrical Manual.

    DC wiring is much more sensitive to voltage loss than AC wiring. That’s whole reason AC was invented and adopted. This voltage loss is also sensitive to temperature, so while rules about the maximum number of conductors in a given size of conduit are designed to keep temperatures down low enough not to start an electrical fire, we’re also really interested in not squandering our electricity by generating electrical resistance heat in the walls.

    For wiring a whole house in DC it really pays to get a good understanding of the unique characteristics of DC and designing to your needs in addition to the code–it would take a whole lot of extra solar panels (with a lot of embodied energy in them) to make up for an ill-designed DC distribution system.

    Also, since some of the biggest energy loads in most homes is refrigeration, the section in Calder’s book on designing and building your own fridge/freezer is invaluable.

    As a side benefit, since it draws on bountiful experience in the boat building world, it may be easier to gain buy-in from building officials when your design falls too far outside the conventional AC-wired home.

    A terrific bonus of maximizing the use of DC and just having a few AC plugs for convenience items is that you can bypass expensive frequency matching DC-AC inverters for grid tie. If you’re going to grid-tie, connect from the grid to a battery charger then to your battery bank. For household AC loads, run an basic inverter off your battery bank. Your DC generation equipment ties into the batteries on the load terminals. Since the batteries separate the grid from your “power station” there’s no need for special planning permission from your utility and no fancy equipment. The drawback is that you are not set up to sell back excess power to the power company so you’ll need a dummy load like an electric hot water heater tank for when your batteries are full and supply>demand. You also won’t get to benefit from net-metering. It would take a huge battery bank and inverter set-up to handle large 220v appliances like an electric clothes drier or electric cooking range, so you could run those directly to your AC panel. It might not be for everyone, but it goes to show there are more ways to go than the standard PV to frequency-matching-inverter-charger net-metering.

    Sorry for the wall of text. I must have some engineer blood in me–I can geek out on systems design a bit.

  4. Sandra

    Aug 5th, 2011

    Great info…I will make sure Chris sees this!


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