How To Use a Voltage Tester | Ask This Old House

[Music] okay heath electrical testers love it because i do a little bit of electrical work terrifies me that i'm going to like to keep myself so i always want to know if something's energized or not no electrocuting yourself and these are very very important these make make it very easy to identify whether something is energized and the importance of that is to make sure that it's off when you're working on it yeah or if it's on if it's wired correctly or if there's a problem going on what's going on and i'm glad to see that a pro like you actually use them because uh i thought it was just mine you just thought it was gonna lick the finger and touch it no i've seen it before all right so what do you want to start with so we'll start with this one this is one of the easiest ones to use this is something a homeowner ought to have it's just a contactless voltage tester now it's not going to tell you what's there for voltage but it's going to tell you something is or isn't energized right so for here we can point to that prong here at chirp we can tell there's something going on there we don't know how much but we know that it's energized somewhere it's energized right and it's not just for um plug it into a receptacle right if you've got a wire exposed or a cord coming in and you want to know if the fans exactly just touch the same thing gotcha okay now the one drawback to these is they're great they're really really good they're not perfect so because it is contactless you can get phantom readings occasionally if you put on the wrong spot you may think it's not energized and it is so you always want to follow up with an actual contact tester if you're going to work on something and by contact you mean it literally has got probes right and you expect those to make contact with the thing either in the receptacle or the cord of the switch that has got the energy exactly so for me i'll use this this is my multimeter this does a lot more than a typical homeowner would need but having a simpler version of this is still a good thing is this a simpler version and this is a simpler version so how does this work so this is simply we'll take that and we'll plug it in and when it lights up it gives you several different levels to tell you what voltage is present so the lighting up tells me that you've got power yeah and then i'm seeing 24 volts 48 volt 120 volt and 240 correct the first three are lit up so that tells me that that's getting 120 volts 120 volts of this yes but not 240 correct okay and so that's going to help you know what that outlet receptacle switch or whatever is getting for power exactly so if you use this first and for some reason it didn't go off you double checked it with this oh wait a minute i really do have power there i want to make sure we shut that off any chance of false or phantom readings for that or with this you shouldn't no this is direct contact this should work gotcha okay and then this cute little guy right here this little guy actually gives you a lot more information than you think all right so i'm seeing a grid on the front it's got a well so there are three indicators yep and then the grid right here it's got different combinations the first one is off middle one's on second so forth exactly what's this telling us so we can't use it on the two prong which is why something like that works well but if you have three prongs this will give you a perfect indication of what's going on so you'll plug this in it'll show which lights are lit up so on on off and on that grid if i may and i look at that on on off says hot neutral reverse did i get that right so we have reverse polarity which means what so that means the black wire and the white wire are actually reversed on the receptacle on the receptacle so when you have a receptacle like this and you wire it there's a specific way to wire it so the brass screw would get the black wire the white screw or the silver screw will get the white neutral wire and the green will get the ground and if you do that correctly you're okay and if you do it incorrectly you'll it'll still work it still works but not properly what do i care if it still works because it's a safety hazard how so so you wouldn't think so you think you'd plug something in it operates what's the difference what does it matter say you have this metal lamp okay we got a desk lamp right here we got a bulb we turn it on we're working and this particular one is wired correctly nothing something something which means correct correct it says correct so so the hot wire is correct the neutral is correct and the ground is correct everything is good in this and that's great but if it was backwards if we were to take that that this is the one that we've already indicated is is reverse polarity reverse polarity right so this is still working this is still working on off no problem we can kind of show here we have power there up to the bulb turn the switch we shouldn't have power there no wait so that's hang on a second that's energized up there that's still energized so reverse so if i were to take this bulb out and i were to touch that right socket right there especially with a lamp like this you have this metal lamp and you have that brass shell right there you're waiting to get zapped why is that happening with the wires reversed because in a socket the center pin wants to be the hot wire it wants to be the black the shell wants to be the neutral right when it's reversed it goes the other way around and it's also the switch is now turning the neutral off and not turning the hot conductor off so there's a little pin in there i'm not going to touch it that's supposed to be the hot the shell is supposed to be the neutral those are now reversed which means the power is coming to the shell correct really if we put it back the way it should be let's put that bulb in okay hang on this is confusing so it still looks like it worked you're like what's the difference still energized go ahead and turn the switch off uh i like it now it's wired the way it should be that center pin is the hot conductor that's been turned off the neutral is now the shell you're not going to get hurt okay so headline here i'm definitely going to have that one in my bag definitely of these two right here you think i should have both definitely this one if you have three prongs if you're stuck with two prongs somewhere that's good to have so you know what's going on all right i'm gonna have all three abundance why not good thank you heath i appreciate it thanks thanks for watching this whole house has got a video for just about every home improvement project so be sure to check out the others and if you like what you see click on the subscribe button make sure that you get our newest videos right in your feed

Channel: This Old House

Views: 341,314

Keywords: This Old House, DIY, Construction, Home Improvement, Ask This Old House, Building, electrical, Heath Eastman, Kevin O'Connor

Id: 0groxS9MaSw

Length: 6min 17sec (377 seconds)

Published: Sun Nov 28 2021