Electrical Usage

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Designing a Home with Low Voltage DC

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Designing a Home with Low Voltage DC
© Copyright 1993 By Charlie Collins From "Ask Mr. Solar" Column Published 6/18/93 Daily Spectrum

Question:What difference in design should I allow when planning a home with low voltage current?

Curt Larson, Long Beach, Ca.

Mr. Solar: Curt, there are several differences in using low voltage current you should consider when you are working on plans for a new home. You should also contact your local building inspector before construction so that you are both clear on your plans for low voltage.

One of the first things to consider is where you are going to locate your batteries in relation to your power generating source, whether it be hydro, electric solar panels wind or a gas generator. Normally you will generate 12 V D.C. power however due to the high line loss you will need to locate your batteries as close as possible to your power source. Line loss is actually voltage drop over the length of the wire and robes you of your voltage when your transmission line is too small.

We suggest locating your batteries outside your home in a building all by themselves that has proper venting for the hydrogen gas that your batteries will give off during use. You should not have any electrical switches, open flame or pilot lights in this area. This area should be secure with a lock so that no one that is not familiar with the batteries has excess to them. This is so that no one will accidentally drop a wrench across the terminals that will cause a large spark. Another reason that you should lock them so that people will not get the acid on themselves, which as you know will burn your clothes or hands. Also if you are using lead acid batteries then you must insulate the area so that they will not freeze if you are building in a winter freeze area. Nickel cadium or Nickel Iron batteries will not freeze until the temperature reaches -35 below zero therefore it is not necessary to insulate them. You can install your batteries inside your home however you must take extra precautions to be sure that they are well vented to the outside of your home. These are the same precautions that you normally should do with your car battery.

You should locate the controls and the inverter close to your batteries to reduce line loss. You may use 12 Volt DC power for your lights and radios as well as small TV's. We strongly recommend that you do this as you will finds that should your inverter fail you will still have lights. Curt, if you plan to wire your home for 12V DC power as we have for lights, radio, TV, etc., then you will need to do several things differently. The main difference is that you must use crimpers on all connectors rather that the usual twist nuts. The low voltage connectors will corrode and after a few years your connections will not be as good as you expect. You should consider running a separate heavy wire to a distant point or points so that you will not have any runs over 50 feet with your normal 12/2 wire. The reason for this is you will experience a line loss with low voltage and a small 12/2 wire will not give you the voltage at a long distance. It would be an excellent idea for you to use different color wire and thermal boxes so that later you will know what type of current is in each. There are special UL approved switches and lights made especially for low voltage DC power. You should use them because the AC type will disintegrate they are used with DC power. Wiring your home for 110 AC power from your inverter is the same as wiring your home using grid power.

If you follow all the above suggestions you will have a trouble free system for years to come; however remember to always check with your local building inspector.