Denray Posted May 7, 2014 Report Posted May 7, 2014 How do you tell if open ground when the lights show hot/neutral reverse. Open ground would just have the middle yeller light on. Click to Enlarge 30.93 KB
John Kogel Posted May 7, 2014 Report Posted May 7, 2014 Try that one agin, Denny? No comprende. [] Only the center light on tells you there is no ground. If you plug the cheezy 3-light tester into a 2-prong adapter, only the center light will light, no matter which way you plug it into a receptacle. So it can't tell you if hot and neutral are reversed on an ungrounded outlet. That is not what you asked, tho. To find reversed polarity on a polarized but ungrounded receptacle, hold your finger over the narrow slot and bring you voltage sniffer in to the wide slot. It will not ring, then ring when you remove you finger. Thanks Trent for enlightening me on that one.
Denray Posted May 8, 2014 Author Report Posted May 8, 2014 It's a three pronger and it's showing reverse polarity. But what if it had an open ground too. The reverse thing uses that center light, but so does an open ground. Perhaps it has an open ground and reverse polarity. How would you be able to tell that?
AHI in AR Posted May 8, 2014 Report Posted May 8, 2014 If you're in doubt just pull the plate off and look. BTW, those 3 light testers can't find a bootleg ground. Looking can. Or use a better tester such as a Suretest.
John Kogel Posted May 8, 2014 Report Posted May 8, 2014 It's a three pronger and it's showing reverse polarity. But what if it had an open ground too. The reverse thing uses that center light, but so does an open ground. Perhaps it has an open ground and reverse polarity. How would you be able to tell that? What I said, use your voltage sniffer, or what he said, ShurTest or pull covers.
Marc Posted May 8, 2014 Report Posted May 8, 2014 How do you tell if open ground when the lights show hot/neutral reverse. Open ground would just have the middle yeller light on. Click to Enlarge 30.93 KB As I understand the lamp characteristics, the left lamp would illuminate brightly and the other two only dimly (because they're in series with each other). Download Attachment: Receptacle_tester_wiring_diagram.pdf 33.68?KB Marc
mjr6550 Posted May 8, 2014 Report Posted May 8, 2014 I've always thought that you cannot determine if there is an open ground using a three-prong tester.
Jim Katen Posted May 8, 2014 Report Posted May 8, 2014 How do you tell if open ground when the lights show hot/neutral reverse. Open ground would just have the middle yeller light on. Click to Enlarge 30.93 KB You don't. Three light testers are ok as a quick go/no go look at a receptacle. They are completely useless if there is more than one defect in the receptacle wiring. They cannot detect multiple defects. BTW, I've found the Suretest to be very unreliable at detecting bootleg grounds.
Jim Katen Posted May 8, 2014 Report Posted May 8, 2014 As I understand the lamp characteristics, the left lamp would illuminate brightly and the other two only dimly (because they're in series with each other). Download Attachment: Receptacle_tester_wiring_diagram.pdf 33.68?KB Marc What's all that stuff on the right side of the diagram and why are there four switches?
Marc Posted May 8, 2014 Report Posted May 8, 2014 As I understand the lamp characteristics, the left lamp would illuminate brightly and the other two only dimly (because they're in series with each other). Download Attachment: Receptacle_tester_wiring_diagram.pdf 33.68?KB Marc What's all that stuff on the right side of the diagram and why are there four switches? It's a different product than the OP is using, apparently. I use it as representative of the 3 prong tester. Marc
John Kogel Posted May 8, 2014 Report Posted May 8, 2014 As I understand the lamp characteristics, the left lamp would illuminate brightly and the other two only dimly (because they're in series with each other). Download Attachment: Receptacle_tester_wiring_diagram.pdf 33.68?KB Marc What's all that stuff on the right side of the diagram and why are there four switches? The R's are resistors. R1 is 2000 ohms with a rating of 25 watts, big one.Switch 1 is the test button for GFCI, shorts the Line to Ground through the bulb. The R1 slows the electrons down so it isn't a dead short which would fry the tester and your hand. The Switch S2 is for converting to a European 240 volt tester, must be an internal setting. Marc, I wonder if S2 and S3 could be switching diodes that close when they are grounded? That could be some other gizmo tester. Check out this schematic. Click to Enlarge 39.3 KB No test button shown on this schematic. I am tired of this now.[?]
gtblum Posted May 8, 2014 Report Posted May 8, 2014 What's the difference? If it's screwed up one way, it's screwed up. Let an electrician figure it out!
Scottpat Posted May 8, 2014 Report Posted May 8, 2014 I agree with Jim, the Suretest is not always reliable with bootleg grounds. I have a three light tester and I use it from time time, they are quick especially with those dang childproof outlets. My tools of choice are a voltage sniffer and a cheap two prong neon light tester. Sniffers are great at detecting open or no grounds and reverse polarity..
Ben H Posted May 9, 2014 Report Posted May 9, 2014 How do you tell if open ground when the lights show hot/neutral reverse. Open ground would just have the middle yeller light on. Click to Enlarge 30.93 KB You don't. Three light testers are ok as a quick go/no go look at a receptacle. They are completely useless if there is more than one defect in the receptacle wiring. They cannot detect multiple defects. BTW, I've found the Suretest to be very unreliable at detecting bootleg grounds. I may be really lucky, but I catch a few every month with mine. I do get false positives though. So I pull the receptacles and double check.
rkenney Posted May 9, 2014 Report Posted May 9, 2014 How do you tell if open ground when the lights show hot/neutral reverse. Open ground would just have the middle yeller light on. Click to Enlarge 30.93 KB John Kogel's diagram is most common wiring for those testers. If there is an open ground only the center light will light regardless of the polarity of the other terminals. At that point reversed polarity doesn't even matter the circuit needs repair. (so, if you show reversed polarity, you can't have an 'open' ground) John's technique with the 'sniffer' works and will indicate reversed polarity if you want to go to that much trouble. The sure test lights are driven by a microprocessor so there is a lot more flexibility in lighting possibilities. No ground is indicated by lighting all three neon lamps. A little thought here and you realize what can you do to that display and indicate - open ground, and some other problem? fortunately the display also indicates a ground problem with one of the additional functions. There are only eight display possibilities with three light testers, cheapo or Sure Test, after that you need further investigation.
Jim Katen Posted May 10, 2014 Report Posted May 10, 2014 . . . I may be really lucky, but I catch a few every month with mine. I do get false positives though. So I pull the receptacles and double check. Wouldn't that pretty much be the definition of unreliable?
AHI in AR Posted May 10, 2014 Report Posted May 10, 2014 It's not 100% reliable but I have caught problems with mine. Most of the false positives I find occur in receptacles close to the service panel -- just as the owner's manual tells you will happen. I have found that mine doesn't find all true bootlegs either. If the Suretest doesn't alert to bootlegs and then you look inside the panel and find a lack of ground wires it's time to take off some receptacle covers.
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