About Brownouts and Single Phasing

Brownouts and single phasing are terms used to describe common problems with the power entering a machine or a building. They are a common cause of compressor failures in commercial air conditioners.

Brownouts

A brownout is when the voltage being delivered drops below the minimum acceptable voltage.

The industry standard for judging the acceptability of the incoming voltage is that it should be no more than 10% above or below the air conditioner's nameplate voltage. For example, it would be very common in the United States to have a nameplate voltage called 208-230 volts. That means that the acceptable voltage range for that kind of unit would be 90% for 208v on the low end and 110% of 230v on the high end. This means the 187v-253v is the acceptable voltage range for a 208v-230v unit. If the incoming voltage is less than 187 on any of the three incoming power lines, it would be described as a brownout. When this problem occurs, it's almost always a utility company problem. Running equipment with a low voltage shortens the life of electric motors and may make the equipment unreliable.

There is a related problem called voltage imbalance. For air conditioners, the three incoming power lines should all have voltages within 2% of their average. If the voltage of the power line with the greatest difference from the average of the three voltages, is different by more than 2%, it is called imbalanced or unbalanced. This is sometimes caused by an unbalance of the electrical loads in the building. Running equipment with a voltage imbalance shortens the life of electric motors.

Single Phasing

Single phasing happens in commercial applications where three-phase power (i.e., when the machine is powered by three incoming power lines) is common. If one of those lines has no power while the other two do, it's called single phasing.

Single phasing is a critical failure of the power to the motor.? It will often result in blown fuses. A machine that runs under single phase conditions will burn out motors in a short time.

What do we do when we are faced with one of these problems?

The first thing to do is to determine if the problem is isolated within the machine, or if the incoming power to a machine or to the building is a problem. If the incoming power to the building is a problem, the first thing to do is shut off the power to all the equipment in the building. Leave it off to prevent damage to the equipment until the correct power is available to them. Next, someone must call the power utility. They will resolve it.

When these problems are limited to power to one air conditioner, it means that there is a problem in the circuit braker panel or the wire running the unit. An electrician could be called to resolve that issue. They would be replacing a fuse or circuit breaker or repairing a wiring connection problem.

When the problem is within the unit, it would be a fuse, terminal block, contactor, or wiring connection problem, usually burnt wiring. An HVAC technician would resolve these problems.

In areas that experience brownout or single phasing with their incoming building power, It is possible to protect equipment. A device called a "Phase Monitor" is the standard solution to repeated incoming power episodes. The phase monitor watches both the voltage and for a loss of a phase, and will shut the unit off as a safety control.

To see if a phase monitor would be a viable solution for you, contact #HeliosServicePartners.

Please DM us or email [email protected] Let us help you avoid the risk of brownouts and single phasing.

https://heliosservicepartners.com/your-partner