Home Electrical Basics: Tools and How to use them

Tim says:

Now that we’ve gone over the terms and all important safety (You read that, right?), we can get into the tools we’ll actually use for basic home electrical repairs.  The list is pretty short, and odds are you already have most of the items:

–Non-Contact Voltage Detector: This wonderful device does one thing and one thing only….which is alert us to the presence of dangerous voltage.  If you don’t have one already, I strongly suggest picking one up.  Thankfully, they’re quite inexpensive compared to a DMM.

– 5 in 1 Screwdriver: This item most folks already have, because well, it’s a screwdriver.  The 5 in 1’s are handy because they have all the different size and type of bits you may need all self contained.  If you have just a plain philips and standard set, those work just as well.

– Needle-nose Pliers: Again, most folks will already have a set of these, but if not they’re quite inexpensive as well.

– Electrical Tape: Nothing fancy here, just a plain roll of good ‘ol black electrical tape.  Comes in quite handy for most repairs.

– Digital Multi-Meter: (Optional): Abbreviated as DMM, this small device allows us to read things like voltage and resistance.  Higher end models also include the ability to read current, capacitance, frequency, and check diodes, but that’s beyond what we need. Having a DMM is handy, but not necessary for most repairs.

And that’s it!  Told you it would be short.  Just about all home electrical repairs can be performed with just these 5 ( or 4 if you omit the DMM) tools.  Now I’d like to cover a few of them on their usage in a little more detail.

Here is a standard Fluke non contact voltage detector.  A decent one shouldn’t cost much over $20, and there are many out there for purchase that work just as well.  Two things you want to look for when shopping for one is that it is CAT II rated or higher  (as defined by the International Electrotechnical Commission.), and that it has some sort of independent verification (should have UL, CSA, or TUV marked on it).   Think of those ratings as a quality assurance that the product will perform as expected.

In practical usage, what this device does is flash a red light and, depending on the model, beep at you when in the presence of at least 90V ac.  This is handy because most households use either 120v or 240v ac.  Since household electricity has the nasty habit of being invisible, this device will enable us to verify that no voltage is present before we start work.

A standard Digital multi meter will run anywhere from $15 to well over $1000.  The high dollar ones are intended for industrial and professional use and aren’t necessary (thank heavens) for home use.  The basic functions you want to look for are AC/DC voltage and resistance(ohms) measurements.  Again, you’ll want to look for the same ratings as on the non contact voltage detecter (at least CAT II and with UL approval).  The non-contact voltage detector will be used the bulk of the time, but what the DMM is good for is in helping to troubleshoot problems.  For example if you have an outlet in which the alarm clock seems to work in, but the lamp seems really dim, you could use the DMM to check the voltage reading of the outlet.  It should be between 110-120v and if it’s not, it’s time to change out that outlet. The resistance setting, indicated by the Omega symbol for ohms, can be used to check continuity between two points.  This could come in handy for checking to see if a light bulb is good before installing it or to verify that motor isn’t shot on the vacuum cleaner.  Another outstanding use for the DMM is in troubleshooting automotive problems like a dead battery or a non-functioning alternator.

Let’s go over a scenario in which we’ll use the above mentioned tools:

Say there’s an light switch that’s been giving you grief because it sometimes just doesn’t want to play.  Here’s what you’ll need to do:

First, determine that the switch is actually getting power (and not just a tripped breaker).  To do this, remove the light switch cover using the 5 in 1 screwdriver.  Don’t worry about shock dangers yet, the switch is held in place by two more screws.  This is just giving us access to the wiring.  Next, turn on your non contact voltage detector and hold it near each wire you see.  It’s ok if it touches the wires, as the tip is plastic and won’t cause any harm.  The voltage detector should blink red at this point indicating electricity is present.  Next you’ll need to go the distribution panel and turn off the associated breaker.  Your breakers are all correctly labeled, right?  Don’t worry, mine weren’t either, but I’ll go over in a future post on how to remedy that.  For this example let’s say everything in the ‘ol “fuse box” is clearly marked.  After turning off the right breaker, you’ll once again go back to the switch and verify that the voltage is gone by re-checking with your voltage detector.  If after this check there are no flashing red lights, then all is safe to proceed.  Next, use your screwdriver to remove the switch from the housing.  At this point you’ll be able to gently pull out the offending switch just far enough to access the screws on the side holding the wiring in place.  Before removing the wires, make a note of which color wire goes where, so when you install the new switch you’ll know where they go. As a rule, the black wire is the hot, the white wire is the neutral, and the green one is the ground.  Loosen the screws to remove the wire.  Now that the bad switch is out, you can replace it with a new one.  Here’s where the needle-nose pliers will come in handy…  Household wiring is notoriously hard to bend due to being single strand, so the needle-nose pliers are used to help get the wire back around the screw terminal.  Once all the wires are back in place on the new switch, take the electrical tape and put a few wraps around the side of the switch so it covers the wire terminal screws.  This is an added safety measure against future shorts.  Push the switch back into the enclosure and secure it with the two screws and finally replace the switch cover.  Last step is to turn back on the breaker and finally enjoy a functional light switch as Edison  intended.

I know I glossed over that fairly quickly, so if you’re scratching your head on a few parts don’t worry. It was only intended to briefly show how the above mentioned tools would be used for a common household problem.  Now that safety and tools are covered, we can start to go over in depth how to go about curing any electrical ailments around the house.  Stay tuned!