Column #862 09/03/11
On The Level
Q. Seems just about every time we have a hard rain, like during Irene last Saturday, the circuit breaker in our hall bathroom kicks off. The circuit breaker is the one that doubles as an outlet. Obviously this should not be happening but is this a sign of real trouble? We lost power for only a day but when it came back on the breaker was tripped. What can I look for as to the reason this is happening? Would you recommend I contact an electrician to take a look? The home is 15 years old now. This has happened just over the past year or so.
A. The circuit breaker in your bathroom is called a Ground-Fault Circuit Interrupter (GFCI) and is a safety device designed to protect you and not the circuit. They began to be required to be installed at certain locations in the home beginning in the late sixties around spas and swimming pools. As the years advanced other household locations were added in response to studies concerning accidental electrocutions in the home. GFCIs are designed to sense the current passing through them and when they sense a problem in the range of four to six thousandths of amp, they trip out. Putting that in perspective, 20 thousandths of an amp across the heart muscle of an adult, healthy male will kill him—eighteen thousandths of an amp for a woman. That’s no joke.
The newer the home, the more places you are likely to encounter them. We recommend older homes be retrofitted with GFCIs at baths, garages, kitchen counters, workrooms etc—all the places where a new home would require them. They are cheap, easy to install, save lives and are probably second only to smoke alarms in their life saving value. I know they have saved me more than once working with power tools. If you look at the back of a GFCI outlet as it comes out of the box you’ll see there are places to install wires from the power source and places to wire outlets down the line from this outlet. The power side is called the line and the downstream outlets are called the load. What this means is that if you wire an outlet through a GFCI type outlet, the outlet wired through is also protected by the GFCI. That means if the downstream outlet is presented with a condition that would cause a GFCI to trip and open the circuit, cutting off power, then the GFCI through which the outlet is wired will trip.
The outlets that are wired through and protected by a GFCI outlet are supposed to marked with a little sticker or even a magic marker that says, “GFCI Protected”. In a house the age of yours it’s likely that the sticker or mark either was never there or has worn off. Modern GFCIs say on their packages that you may wire as many as six outlets through the GFCI. Electricians will frequently wire outlets in locations that require GFCI circuitry through one single GFCI that they will place in a bathroom, powder room, garage or near the panel box. The GFCI outlets are less expensive than GFCI breakers that install directly into the main panel so whenever they can they use the outlet style GFCIs to satisfy the code requirement.
I’ll bet that the reason your bath GGFC trips when it rains hard is because the outlet that is causing the tripping is wired through the bath GFCI but is located outside somewhere. Take something to plug in, such as a light, and with the bath GFCI tripped open go looking for the outlets that are protected by this GFCI. The outlets that test dead will be ones governed by your bath outlet. Double check by resetting the bath GFCI and go back to the ones you found dead and see if they are now hot. Check the covers and outlet weather caps of the exterior outlets protected by the bath GFCI to see if they are rotted, loose or missing. I’ll bet you find some problem along these lines at some point in the chain. Repair the bad weather barrier on the outlets and wait for the next hard rain to see if you’ve solved the riddle.
Should you feel moved to pull out an outlet to check the wire attachments or replace cracked or broken outlets be sure to shut off the circuit at the circuit breaker in the panel box. Prove that the circuit is dead by plugging a radio into the bath outlet with the volume up to where you can hear it at the panel. Flip breakers until you hear the radio go silent. I don’t necessarily believe the listing of what breaker controls what found on the panel door— I learned that the hard way. If you don’t feel comfortable doing this then call an electrician. The good news is that when the problem presents itself the GFCI does its job and trips the circuit open eliminating any further danger. But any tripping GFCI is a signal that something is wrong and it behooves you to find the cause and fix it.
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