top of page

Brown Out Conditions - Effects on Electrical Equipment

A brownout is a temporary interruption of power service in which the electric power is reduced, rather than being cut as is the case with a blackout. Lights may flicker and dim during a brownout, and the event also often wreaks havoc with electrical appliances such as computers. One could consider a brownout the opposite of a power surge, an electrical event in which a sudden burst of power enters the system.

There are a wide ranges of causes for brownouts. Just like blackouts, overloads on the electrical system can trigger a brownout, as the generating facility is unable to provide enough power. It can also occur when events such as storms disrupt the distribution grid, or when there are other problems in the system. Brownouts can last for a few seconds or a few hours, depending on the type of brownout and how quickly a power utility can get full power running again.

In some cases, a brownout is actually deliberate, in which case it is known as a voltage reduction. Voltage reductions are undertaken when utilities sense that a disruption in the grid may lead to serious problems. Rather than instituting rolling blackouts, the utility may temporarily cut voltage to some customers in an attempt to stabilize the grid and to allow reserves of power to accumulate again.

During a brownout, utility customers should turn off appliances like computers, as the irregular power supply can damage them. It is also a good idea to turn off lights, leaving one on to alert the customer to the restoration of full power. You may also want to check with the neighbors; if your house is the only one out, there may be a problem with the power supply in your residence, and you should take a look at your circuit board and breakers. You may have inadvertently caused a brownout by overloading your home's capacity to carry power, for example.

Here is one way to calculate amperage with two knowns that are normally readily identified on your equipment

The Formula - Watts (P) divided by Volts (E) = Amps (I) or P/E = I

Example under normal conditions = 7000 watts / 240 volts = 29.1 amps

Example with a voltage reduction = 7000 watts / 210 volts = 33.3 amps

**Many times a a reduction in voltage causes equipment running on the cusp of their circuit breaker rating to trip the circuit breaker or other overcurrent devices (i.e. fuses) because of the additional current caused by the reduction.

This happens very much with air conditioning equipment. A contributing factor is when the equipment is not running at it's designed nameplate ratings in regards to amperage because of it's age or equipment neglect such as dirty condenser coils or blocked air intake. Yearly maintenance is very important. Avoid costly service calls when very little can be done if your equipment is running efficiently and generally the condition will return to normal after the brown out ends. It is a good idea to have spare fuses ready if your equipment disconnecting means has them installed. Not all equipment will have fused disconnects so you'll want to check. Turn off your main circuit breaker to the equipment and open the disconnect switch by the equipment. If you have fuses they will be visible.

Newer high efficiency equipment is very sensitive to brown out conditions because of the advanced electronics.

Use other equipment like dishwashers, electric clothes washers and dryers in the evening when temperatures are cooler putting less stress on the grid minimizing the need for the utility co. to turn down the voltage to it's customers during the day.

If you feel your home or business is affected, you can call your utility for information. If information about your brownout is not available, report it to the utility, as they may not be aware of the problem being it could be an issue with power lines or transformers.

bottom of page