What Is 120 Volt Power

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In North America people variously describe the electricity available from their household receptacles as 110 and 120 volts, using the terms interchangeably. For all intents and purposes, the terms mean the same because transmission losses and power drops can reduce the 120-volt power supplied by the power company to as little as 110 volts by the time it reaches a receptacle.

The true voltage at most receptacles is usually somewhere between these values.

Advertisement . Video of the Day . There is no international standard for the voltage of electricity supplied to residences and commercial establishments. In many countries, including those in Europe, 240 volts is the standard, while in Japan the standard is 100 volts.

In North America, power comes into a home's service panel (breaker box) through two cables, each at a voltage of 120 volts. Lighting and standard appliances require the power from only one of these cables, but when it is necessary to run an appliance that requires a higher voltage, the cables can be combined with special wiring and fixtures to provide 240-volt power.

Advertisement . The rated voltage input in each cable the power company feeds to a service panel is 120 volts plus or minus five percent due to fluctuations in transmission loss in the power lines. This means that the power at the panel can be as low as 114 volts. As the electricity encounters resistance in conductors and does work while passing through electrical devices along its path, its voltage drops still lower.

In a house with extensive circuitry, it is not unusual to get a 110 volt reading or less at receptacles far from the panel. Advertisement . Most appliances are rated for 120 volts, so if your receptacle is supplying electricity at a smaller voltage, the worst that can happen is that it won't work as well.

Chances are better, however, that you won't notice any difference in its performance.

If a nameplate on an appliance shows that it has a 110 plug, this most likely means that the appliance is designed to operate at 120 volts, but will continue to operate normally if the voltage drops to 110 volts.

You may begin to notice a loss in performance in some appliances if you plug them into a long extension cord. Advertisement . The receptacles and plugs used in countries with 240-volt standard voltage are shaped differently than those in North America so you can't confuse them; receptacles and plugs in Japan, where the standard is 100 volts, are shaped the same.

100 vs 120 volts is different enough to affect the operation of a Japanese appliance plugged into a North American circuit.

In particular, electric toilet seats, or washlets, made in Japan have been known to overheat and catch fire. On the other hand, the voltage in Japanese circuits isn't large enough to operate North American appliances at their full power. Advertisement . The power converter is an essential component in an RV’s electrical system.

Typically, coaches have two essentially separate electrical systems; one that provides 120 volts AC to high-power consumption, high-wattage appliances such as coffee makers, microwave ovens, hair dryers, air conditioners, etc. The other, low-voltage part of the electrical system provides 12 volts DC to lights and other items which don’t have high current draws, and are sometimes powered by onboard batteries (which provide power when you’re not hooked up to an outside power source or generator).

When you are connected to campground power or running off a generator, the power converter changes the 120 volt AC power to 12 volts DC, which is compatible with the low-voltage electrical system and batteries.

This electricity supplied by the converter can take the place of the power from the batteries, and can also recharge them. Many basic single-stage converters, typically found in older and lower-priced coaches, are still in use. They don’t have the sophisticated internal circuitry to properly charge and condition batteries.

Some converter models supply only a fixed voltage of around 13.2 volts, which prevents batteries from reaching full charge and also shortens their service life. Modern multi-stage charging circuits typically include four operation modes: boost, normal, equalization and storage (or float).

Related article:RV Battery Basics: A Beginner’s Guide. Batteries have become quite expensive, and faulty charging by the converter can be both inconvenient due to loss of power, and costly in terms of ruining batteries.