Tuesday, June 16, 2015

Electric Receptacle Safety Checks, Easy and Inexpensive

Gardner Bender Receptacle Tester and Circuit Analyzer GRT-3500

Buying your first house can be an educational experience. By the time you get to the fifth or sixth purchase, you notice patterns – and one such pattern seems to be how many do-it-yourselfers are confused about the simple task of wiring an electrical outlet. I’m happy to say that not a single outlet in the house we just sold was wired with reverse polarity. Not so with the new house, which features a finished basement where work was done by “an engineer.” I suspect an engineer of the software variety, since an electrical engineer is pretty unlikely to install the light switches upside down. Ya think?

Oh, well, at least he didn’t use lamp cord instead of 12-gauge Romex® to control ceiling fans on 20-amp circuits – been there, seen that, about three houses ago…

Once the dust has cleared from moving across country, I’ll need to get into my new electrical system and undo the mis-wired outlets. That means I’ll dig out my trusty electrical circuit tester, a Gardner-Bender GRT-3500. To use the device, which looks like a rather chunky black three-prong plug, just plug it into the receptacle. As long as the circuit is hot, I’ll get an immediate scan of the circuit. Just read the interpretation off the body of the plug to learn the state of the outlet. Since there are (at least in theory) three wires in the system - hot, neutral, and ground - six results are possible: 

  • Open Ground: either the ground wire’s not connected to the plug or ground is broken somewhere in the wiring. 
  • Open Neutral: the return wire (usually white) isn’t connected to the plug or the circuit is open somewhere. 
  • Open Hot: No light at all means there's no power to the plug the hot (black) wire isn't connected. You also see this if the breaker’s tripped or the plug’s controlled by a switch that's currently in the OFF position. 
  • Hot / Ground Reversed: The bare and black wires are connected to the wrong terminals, white is correctly connected. 
  • Hot / Neutral Reversed: The black and white wires are connected to the wrong terminal. 
  • Correct: All three wires are connected to the right terminals. Whoopee! 

The serious problems - Hot / Neutral reversed or Hot/Ground reversed - are flagged with a red light; the other error conditions only cause amber lights. 

Hot / Neutral reversal, also known as reverse polarity, is probably the most common error the tester catches. While few (if any) electrical devices used to care much whether current runs left to right or right to left, almost every electrical device made in the past few decades has a polarized plug for safety's sake. They can only be plugged into (modern) outlets in one orientation, a design to ensure that should there be a short in the device, exposed metal parts won't carry the current. A socket with reverse polarity is considered an electrical shock hazard, which is why they're noted on pre-purchase home inspections. Electronic devices, as opposed to simple electrical devices like toasters and lamps, are more sensitive to the condition as well. Fortunately, reverse polarity is fairly easy to fix: just switch the black and white wires. 

This particular tester doesn't analyze GFCI (ground-fault circuit interrupter) receptacles, which are required in wet areas (bathrooms, kitchens, garages, basements...). Gardner-Bender does have a tester that does so, which costs about half again as much. 

The only problem I've had with it mine is that the prongs seem to be a little closer together than normal, so it can be hard to insert into sockets. Unlike older models, the chart is printed on both sides so you can read it even if a plug was installed with the ground on top, which some electricians use to indicate a switch-controlled circuit. And some DIYers just do out of ignorance.


PLUS: easy to read, easy to use
MINUS: doesn't test GFCI outlets for faults, prongs set rather close

What They're Saying: For only a few dollars a Gardner-Bender GRT-3500 can test your home's electric receptacles for reverse polarity or improper ground. 

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