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I'm wondering something. It's purely theoretical.

Let's say I'm in home automation etc and I've got lots of little modules, for examples to control lights, access codes, doors locks, etc... All these modules uses DC voltage. But houses mostly are wired with AC circuits.

Does it sound ok for you to have some tranformers in the basement, (for example 5VDC/10A, 9VDC/10A, 12VDC/10A) and then wire the house with DC circuits in addition of the classical AC circuit ? Are there some limitation ? (cable length) Or any specific care about ?

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  • \$\begingroup\$ Of course it's possible. With heavy enough gauge wire the copper losses will be minimal. My main concern would be the legality of a private individual running additional electrical wiring in their house, and how it would affect the resale value. I would talk to a building inspector and electrician in your local jurisdiction to make sure this is done properly. \$\endgroup\$ – Matt Young Jan 5 '14 at 16:26
  • \$\begingroup\$ I agree with the above post. You could certainly do this, but there are laws against modifying homes without permits - especially when it comes to structural or electrical modifications. \$\endgroup\$ – sherrellbc Jan 5 '14 at 16:28
  • \$\begingroup\$ Ok thanks, it's a purely theoric question, I won't do that (for the moment :p) \$\endgroup\$ – Emmanuel Istace Jan 5 '14 at 16:40
  • \$\begingroup\$ alexan_e's answer will kill you. This is a lethally dangerous "solution". It is only suitable when the power supply and ALL operated LV circuitry is fully enclosed and not accessible by users. In the context of the question it is both dangerous to life and not a valid answer. \$\endgroup\$ – Russell McMahon Jan 6 '14 at 1:55
  • \$\begingroup\$ Distributing energy at high voltages and converting down near point of use greatly minimises transmission loses and or wire size needed. \$\endgroup\$ – Russell McMahon Jan 6 '14 at 1:56
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You can find some information on Low Voltage wiring in NEC Article 720 "Circuits and Equipment Operating at Less Than 50 Volts.

Article 720 is relatively brief and basically states that conductors should not be smaller than 12 AWG. 12 AWG is some hefty wiring for the low voltage you are considering.

Article 725 covers Class 1,2 and 3 "Power Limited Circuits"

A Class 1 circuit is one that is under 1000 VA. The maximum VA you listed is 120 (12V * 10A). As long as you have your circuit properly fused or on a circuit breaker you can classify your circuit as a Class 1 under Article 725.

725.25 States that you can use 18 AWG and 16 AWG in an approved raceway or cable.

Typical house wiring of this type is called bell wire. This cable usually has a brown outer jacket and has solid conductors (one white and one red) It is also available with more than 2 conductors and is used for wiring of doorbells and thermostats.

If you anticipate regular circuit loadings of 10Amps I would consider using 16 AWG wire. Otherwise I would think 18 AWG would be fine.

Edit: I see that 725.23 " Class 1 Circuit Overcurrent Protection" states that circuit amperage for 18 AWG wire shall not exceed 7A. Circuit Amperage for 16 AWG wire should not exceed 10A

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