Home >> Science & Nature >> Science

The Effects of Low AC Voltage

Electricity fills dark homes with light, enough to find the TV remote and start the microwave oven to make popcorn while basking in air conditioning. This enormous demand for electricity in the home strains the system. When this consumption occurs, some areas may experience brownouts, in which voltage is reduced because of an overburdened electric grid.

Power, Amperage and Voltage
- There is a very simple relationship between power, amperage and voltage: Power, measured in watts, is the product of amperage and voltage. Given the same voltage, a device that uses twice the amount of amperage as another will use twice the amount of power. If power is constant and voltage decreases amperage will increase. This is precisely what happens when there is an unexpected drop in voltage.
Increased Current Draw
- Suppose you have a drill designed to operate at 120 volts and 420 watts. That means it normally draws 3.5 amps of current to maintain 420 watts of power. If voltage is reduced to 100 volts, the device will still require 420 watts of power. It can maintain this amount of power if it draws 4.2 amps instead of 3.5. When voltage drops, electric devices draw more current to maintain the same power.
Circuit Breakers
- The circuit breakers in your home are designed to protect you from overtaxing your electric circuits. If you ever tried to plug in your lamp, stereo, air conditioner and hair dryer to the same circuit, you probably ended up sitting in the warm quiet dark with wet hair, because you blew the circuit breaker. You were trying to draw more current than that circuit could safely deliver, so it shut it down. If voltage is reduced, circuit breakers may flip even if you did not overburden a single circuit with too many devices. At normal voltage, the circuit could handle your air conditioner by itself. At reduced voltage the air conditioner might draw too much amperage for your system to handle.
Overheating
- Circuit breakers do not leave you in the dark just to inconvenience you. They are there to prevent a fire. When a circuit or device is drawing more current than it is designed for, it heats up. Your home has fuses or circuit breakers to prevent the house from burning down. Individual devices may still operate at reduced voltages, but they may run hotter. Power tools will not last as long nor run as efficiently at reduced voltages. Electronic equipment can be damaged operating at low voltage. If the lights are dimming, it's probably best to limit electric device usage until normal voltage returns. It's safer and your things will last longer.

Science