what causes electrical low voltage?

Question

Residential electrical circuit has a low voltage reading in the light fixtures only. What could be the cause of this?

Answer 1

The laws of physics.

Since superconductors have not been perfected for commerical or residential applications, all of the wiring between you and the electric utility has resistance.

Note: For purposes of this answer I am ignoring the complexities of reactance, power factor, etc.

Electricity flowing through a conductor with resistance will cause a voltage drop.

Voltage Drop = Amps x Resistance of conductor(s)

The resistance of the conductors is based on the conductor size and length.

Basically you've either got too much load or trying to go too far.

Since you mentioned low voltage readings, we will assume you have a volt meter and know how to use it. Just keep in mind that the AC supply in your home is more than capable of killing you.

You will want to measure the voltage at an outlet near the main panel to get an idea of the service entrance voltage.

A second measurement at the light fixtures will show you the voltage drop through the wiring in your home. If you turn off all the lights on that circuit, the voltage should rise to the same level as the main panel.

As you compare the voltage readings, keep in mind that the laws of physics exist outside your home too. The utilities wiring and transformer are also affected by the size of the load and the length of the wires.

If the voltage at the main panel is low, the electric utility may be responsible for correcting the problem on "their side of the meter". Low voltage from the utility is sometimes referred to as a "brown out". This is most likely to occur during periods of peak load when the electrical system is loaded the most.

Answer 2

Low Voltage Electrical Supply

Answer 3

It could be that the light fixtures are on a specific phase. Let's use phase "B" for example. Now, Phase A is hot, but let's say phase B is dead. Now you've got a hot water heater, a furnace, or some other 240volt appliance that it taking the voltage from phase A, going through the appliance, and giving you a dropped voltage onto phase B. My advice, turn all two-pole breakers off and test the voltage on each phase to ground/neutral on the incoming main wires. Normal is 120 on both. If you don't get 120 on both, trace it back and find the dead leg.

Answer 4

Take a cup of water and pour lots of salt into it. Then hold two fingers of the SAME hand into the salt water. Touch both poles of a 9V battery and you will get a shock. The shock could be very weak or quite painful depending on your skin and for how long your fingers were soaked in the salt water. But even with dry hands you can get a shock from low voltage DC if e.g. you have an injury and are bleeding. Electricity flows easily through blood. Never let the current run from one hand to the other.

Answer 5

Residential electrical circuit has low voltage reading, bec they are designed that way. They dont need anything more then 120V. However commercial building would be more like 480/277 Volts. To answer your question, many times the feeder size has alot to do with it as well as the length of the feeder. Hope this helps.

Answer 6

There are many causes of low voltages. Some of them are:
1). Overloading of a particular phase.
2). Cable size.
3). Phase failure
4). Rust and worn out cables.
5). Loose connections.
6). Neutral failure.

Answer 7

To great a load for the power supply or too small a wire gauge in the supply line. In the latter too much power is lost in the wiring, which can cause overheating and fires. CAREFUL!

Answer 8

almost anything

low voltage is all around us