Extra Low voltage, Home Automation Guideline


Saudi Arabia

I want to study and explore Extra Low Voltage systems. Fire Alarm systems and Home Automation and security. I find these areas are less explored by many engineers and I don't want to be one of them.

Can anybody suggest me some good books on these which can give a comprehensive understanding of the subject. I once, read Electrical Wiring by Ray C Mullin which discussed Low voltage in a very detailed manner. Maybe, such kind of book on Extra Low Voltage will make my day.

I want to understand more about Networking i.e how LAN, Data circuits are distributed, to which equipment does Fire Alarm Control Panel connects precisely and equipments used in Home automation and security etc...

PS: Extra Low Voltage is sometimes referred to as Low current system.


Senior Member
Extra low voltage is sort of a catch all
phrase since some jurisdictions don’t agree with the almost universal 50 VAC “limit” belie which shock fatalities are extremely unlikely. It has nothing to do with power limited cases except how it is treated by for instance 70E. I think you are thinking of power limited which is covered in NEC. There are a few different classes but the key is that power (voltage and current) is limited so much that fire hazards are minimized. It gets its own Code Chapter 7 and unlike the rest of the book Chapters 1-3 do not apply unless specifically referenced in Chapter 7. Its fairly well written. Just get the NEC Handbook and read up. There are other”power limited” cases outside of Chapter 7. For instance all dielectric fiber is nonconductive so can be run in any voltage space. Intrinsically safe equipment is power and storage limited (no big capacitors) so that it cannot start an explosion. If it meets this requirement the special hazardous location wiring rules can be ignored and standard Chapter 3 style wiring used. Some things are not in NEC. For instance CAT5 can be purchased with 600 V rating and meets UL 508A requirements (as AWM) but not building Code since it is less than 18 gauge, so can only be run in power limited wire spaces even though it meets the insulation requirement.

Not much to know here except that you need to know and understand the Code, same as always.