Electrical Wiring

You wouldn't want to. The Watts are the reason why.

If you needed to power 2000 watts worth of appliances and you have a 120v system, you'd need a little under 17 amps to do it. A relatively thin 12-gauge wire will handle that much power. To power the same load with 12v current, you need 170 amps--and wire 3/8" in diameter.

The built-in transformer you speak of requires 110 volts. They're known as step-down transformers and are a ratio of the incoming voltage. For example: a 10:1 transformer will drop 100 volts to 10 volts. If you gave it 12V you'd end up with 1.2V.

In short: No to your question.

There are many appliances -- such as Google's servers -- that are designed to run on a 12 VDC supply. Appliances designed for recreational vehicles (RVs) and boats often run on 12 VDC.

In theory, a technician with some knowledge of electronics could convert an appliance that is designed to require 110 VAC and convert it to require only 12 VDC. If you are lucky, the appliance already has a transformer and rectifier that converts input power to 12 VDC, and a technician can simply attach a 12 VDC power plug, cable, and fuse directly in to that point. In practice, you would need some system to prevent accidentally plugging the 12 VDC power plug into a 110 VAC outlet, which would probably destroy the appliance, and also prevent accidentally plugging in both the 12 VDC power plug and the 110 VAC power plug, which risks destroying the 12 V power supply.

A few devices use the AC cycle to derive a time base (50 Hz or 60 Hz), and so cannot work on 12 VDC power alone, unless you use an "inverter" that generates that frequency.

Some devices -- such as air conditioners -- require a lot of energy. Given a particular energy requirement, reducing the voltage by 1/10 means increasing the current by a factor of 10, which requires power lines with 10 times as much copper. Increasing the voltage allows us to reduce the amount of copper used -- which is one reason some automobiles have a "42 V automotive system".

In short: 240/120 V @ 60 Hz frequency.

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In the US, lighting and low-power appliances run at 120 volts plus or minus 10%; meaning 108 volts to 132 volts at 60 cycles per second called hertz (Hz). To get the actual figures for your locality it is best to ask a local licensed electrician or your local electricity supply company.

However, US houses get 240 volts at 60 Hz at the panel. If all the wall outlets were fed with that 240 volts you'd have the lower current and higher power advantage of the European 50 Hz system and it would be safer too, since each "hot" would still be only 120 volts from ground, which reduces the shock hazard compared to some European 230 volt receptacles or socket outlets.

However the most important difference is how the Neutral wire is connected:

240 volt 50 Hz service

Please note: there is no 50 Hz service in countries which use a 60 Hz, such as the US and Canada. The following information is given just for comparison purposes.

A 240 volt 50 Hz appliance can have up to 3 wires altogether:

• one single 240 volt "live" or "hot" wire;
• a neutral wire;
• a safety "earth" or "ground" wire but this is not required if the appliance is of the type known as "double insulated".

The hot wire feeds alternating voltage from the power station to the load and, because the voltage is alternating, the load draws an alternating current. Then the neutral wire returns the current to the power station to complete the circuit.

240 volts 60 Hz service

An appliance that is designed to be connected to strictly 240 volts 60 Hz is connected with only a two-wire cable plus a safety ground wire. (For example 240 volt 60 Hz base board heaters use that.)

The only time a cable with three wires plus safety ground is used is if 120/240 volts is needed in the equipment. (For example kitchen ranges or washing machines which have time clocks or programmers that require only a 120 volt feed.)

Thus an appliance designed to run on a 240/120 volt 60 Hz supply can have up to 4 wires altogether:

• two 120 volt 60 Hz live "hot legs" which run in opposing phase to one another: when one hot leg goes "+" (120 volts positive) the other leg goes "-" (120 volts negative);
• a neutral wired as a "central" common current return conductor:
• a safety "ground" wire but this is not required if the appliance is of the type known as "double insulated".

One of the two hot wires feeds a 120 volt alternating voltage from the power station to the 120 volt load - the clock or programmer - and, because the voltage is alternating, that load draws an alternating current. Then the neutral wire returns the current to the power station to complete the circuit.

Important conclusion

There is a 240 volt voltage difference between the neutral and the hot conductor in the 50 Hz system and only a 120 volt voltage difference between the neutral and each of the hot conductors in the 60 Hz system.

That is why an appliance designed to be connected onto the 50 Hz system cannot be used safely on the 60 Hz system without first having a proper technical inspection done, followed by any necessary modification work done to ensure that the appliance can be operated safely because, in the main breaker box, at the point where the 60 Hz "neutral" gets connected to the ground, this difference will cause serious problems!

A licensed electrician or electrical engineer would be able to consider whether or not a particular large appliance, that was manufactured to work on 50 Hz-only, could be modified to run safely at the higher 60 Hz frequency. However it won't usually be worth the expense of doing the work because it would be more cost-effective to buy (new or secondhand) an equivalent large appliance designed to work on 60 Hz.

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In the U.S. it's 120 volts AC running at a frequency of 60 Hz. It was increased from 110 volts in the 1950s.

The historic reason for 110 volts is the Direct Current (DC) power systems created by Thomas Edison. It is believed he chose 110 volts because that is what his light bulb worked on. Later, these systems were converted to Alternating Current (AC), so you didn't need a power plant on every street corner, but the voltage level wasn't changed, so existing lighting didn't need to be replaced. (At that time they didn't care if they got AC or DC.)

An interesting question is why the rest of the world did not wind up using 110 volts. How did 220/230/240V get started over there?

The US system theoretically could be made as good as the European system (slightly better than, actually) with no infrastructure change except to houses themselves. US houses get 240 volts at the panel through the Black and the Red hots. If wall outlets were all fed with 240V you'd have the lower current and higher power advantage of the European system and it would be safer too, since each "hot" would still be only 120V from ground (not 240V) which keeps the reduced shock hazard advantage. If the wiring has been done correctly it should be impossible for someone to touch both Black hot and Red hot at the the same time by accident.

It was Thomas Edison who promoted the use of (then) 100 volts as some tragic experiences in the early days of power distribution showed that 100 volts was not usually lethal for a shock. Remember that in the early days, single un-insulated wires were strung though ceramic insulators, both exterior and interior, and so there were many more shock hazards present. Each splice was made by wrapping one wire around the other one and soldered. The use of junction boxes was non existent. As technology advanced good, long life, insulation was wrapped around the conductors.

Scroll down to related links and look at "Household AC electrical power in different countries around the world - voltages, frequencies and plug types - Worldmap for AC Voltage and Frequency - Wikipedia".

Nowadays terms Residual Current Device or RCD and Ground Fault Circuit Interrupter or GFCI refer to the same type of electrical safety device.

If there is no fault anywhere in a circuit supplying single-phase alternating power to a unit such as an electrical appliance, machine or other equipment, the current flowing to the unit at any instant in the "hot" or "live" wire should exactly match the current flowing away from the unit in the neutral wire. Similarly, there should be no current flowing in the unit's safety "ground" or "earth" wire.

It is a basic fact of electrical engineering design that all current flowing to an electrical appliance, machine or other equipment from the power generation station via its supply circuit's "hot" or "live" wire should only return to the power station via that same circuit's "neutral" wire.

So, as a result of that basic fact, if any current isflowing in the ground wire, it must be caused by a fault condition and the supply of current to the circuit needs to be stopped urgently. Many years before today's electronic RCDs or GFCIs were designed, much simpler electro-mechanical relays called Earth Leakage Circuit Breakers (ELCBs) were invented so that, if any such ground current exceeding just a few milliamps was detected, they would "trip" - meaning "operate" - to break the current supply to the circuits for which they were installed to protect.

An Earth Leakage Circuit Breaker was the first name given to what is now called a Ground Fault Circuit Interrupter (GFCI) . The original type of ELCB or GFCI was designed only to detect a current flowing in the safety "ground" or "earth" wire.

So the original type of ELCB or GFCI did not check for any difference in current flowing in the live and neutral wires, a difference that would be an indication of another type of serious fault condition. Such a fault can be serious because, even if no current can be detected flowing in the ground wire, the "missing current" may actually be flowing to ground via someone's body!

After miniature electronic circuits were invented the invention of RCDs became possible: an RCD constantly checks for small differences in the currents flowing in the live compared to the neutral wire and for any current flowing in the earth wire. If any such "fault current" is detected, the device is designed to act very fast to shut off the supply of power to the circuit and the unit(s) it is protecting, because the "missing current" may actually be flowing to ground via someone's body!

That is the reason why, when RCDs were invented, most manufacturers of GFCIs adopted the same technology because it offers so much more protection to users than the original GFCI could ever give.

In the US and Canada such devices are still commonly known as "GFCIs" or "GFIs" even though they have the additional "residual current detector" functionality, whilst in Europe and elsewhere the more accurate name of "Residual Current Detector" or RCD has been widely adopted for general use instead of using the name of the originally much simpler GFCI device.

For more information on all these topics see the answers to the Related Questions and the Related Link shown below.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.