Your Friendly Local Electrician

Posts Tagged ‘oncall’

A voltage tester is equipped with two probes and a light bulb but has no power source.  The 120/240 voltage, or neon-light that shows that there is voltage, lights up when voltage is present.  This device is used to find the incoming hot wire when more than one black wire is in a box and to check for proper grounding.

If you attempt to work inside of a service panel, and this is not recommended for those that are not skilled in electrical work, it is necessary to look for any current leakage, for any electricity that is outside of its proper place.  This should only be attempted after all power to the panel has been turned off.  Once you are sure that there is no electricity coming in to the service panel, remove the panel cover.  Touch one of the voltage tester probes to the ground/neutral busbar (bus) (a busbar in an electrical power distribution refers to thick strips of wire that conduct electricity in, for one, a service panel.)  Touch the other probe to an open space first on one, then on the other hot bus.  If the tester lights up, call an electrician.

Once you have checked that the power is off, insert the probes into the slots of the outlet.  If the bulb does not light up, the power is off.  Test both openings of a duplex receptacle (double container.)  After this, remove the cover plate, and touch probes to bare ends of each pair of black and white wires attached to the receptacle.  Tester should not light.

It is necessary to check for grounding.  Grounding is the process of removing the extra electrical charge on an object by transferring electrons between it and some other item of substantial size. When a charged object is grounded, the excess charge is balanced by the transfer of electrons between the charged thing and a ground. A ground simply said is an object which serves as an outwardly substantial reservoir of electrons.  The ground is capable of transferring electrons to, or receiving electrons from, a charged object in order to neutralize that object.

To check for grounding in a receptacle with power on, put one of the probes in the short (hot) slot.  Then touch the second probe to the bare metal cover plate, or to the plate screw, or insert the second probe in the grounding slot, if there is one.  If tester shines weakly or not at all, the receptacle is not well grounded.  Then, with the power off, remove the cover plate and look for a loose grounding connection.

To test for the electric power at a switch, first turn off the electric power to the circuit and then remove the cover plate over the receptacle.  Place one of the probes on the metal box, or if the box is nonmetallic, place one of the probes on the bare grounding wire.  Touch each switch terminal with the second probe.  If the tester lights up, then there is power coming in to the receptacle.  If this is the case, go back to the electrical service panel and turn off the right circuit.

If you need to find the right incoming hot (electrified) wire in an electrical box, cut power to the circuit.  Remove switch, receptacle, or fixture from the electric box.  You need to bend the loose electric wires away from each other and the electric box because you need to keep these wires from touching each other and from touching the box.  After this has been accomplished, restore the electric power.  Cautiously, touch one of the probes to the metal box (or to the grounding wire if the electric box is made from plastic.)  Then touch the second probe to each black wire.  The voltage tester should light at the hot (electrified) wire.

• On Call Electricians.Available in Manhattan, New York (212)461-1429. Residential or Commercial – http://yourfriendlylocalelectrician.com #