Understanding the Basics of Voltage Drop

The reduction in the supplied energy of a voltage source as electric current passes through the passive elements of an electrical circuit is described as voltage drop. Put simply, it is the decrease in voltage as current moves through a wire in an electrical circuit. This phenomenon can lead to serious electrical issues if allowed to get out of hand. What causes a voltage drop and what are its effects? What can you do to avoid issues where this phenomenon is concerned?

Acceptable drop

It is not an unusual thing for some level of energy to be lost to the wire conducting it. But the real problem arises when the voltage drop is greater than set limits. There are voltage drop thresholds for different conductors, depending on type, amperage, load and length. In the US, the National Electric Code (NEC) sets the maximum voltage drop at 5% with a view to ensuring power efficiency. Anything beyond that limit is considered excess voltage drop.


Causes of excess voltage drop


The resistance level of an electrical circuit plays a major role in the degree of voltage drop. The higher the level of resistance, the greater the voltage drop. High resistance, which is characterized by less power reaching the load, is often attributable to the use of wires that are not compliant with code standards. This means the use of a wire that is not suitable for a particular circuit.


High resistance is not only caused by ineffective wires. It could also result from issues at wiring junctions or at outlet terminals. These problems include loose connections in a circuit or poor splices in it. High resistance may also occur as a result of corroded connections in a circuit.


Effects of a voltage drop


This electrical phenomenon can cause electrical equipment to malfunction. Low voltage causes electrical equipment powered with it to work in an irregular manner. If care is not taken, an excess voltage drop can make a piece of equipment to become damaged and stop working. Low voltage may even cause the load to perform harder and this does not make for efficient use of energy.


Voltage drop can cause heat to surge at a high resistance connection. In a situation where sufficient ventilation is not provided or there is a combustible material near the heating connection, a fire incident could result. A good number of fire incidents every year are caused by defective wiring, switches and receptacles.


Protecting against voltage drop


The most important step you can take to guard against problems such as fires that could result from voltage drop is the use of appropriate wires. Since wire that does not meet electrical code standards are responsible for high resistance, it then follows that the use of appropriate, standard wires can help guard against voltage drop. The use of a voltage drop calculator will be helpful in choosing the right wire and size.


There are times when a voltage drop occurs after some major appliances such as refrigerators and air conditioners are turned on. These appliances need and draw significant current to function, possibly at the expense of other smaller appliances and lighting fixtures. This type of voltage drop can be remedied by having dedicated circuits installed for these major appliances.


Voltage drop can bring issues which you will rather wish to do without. Steps should be taken to ensure that this electrical phenomenon is guarded against — this will very likely require the help of qualified electricians.

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