Retired Techie
Getting older, not necessarily wiser!
Smoking Outlet
Published on March 11, 2022 at 7:58 am by LEWIntroduction
To be honest, I did not actually see the outlet smoke, it was reported to me. When I got on scene the circuit had been disconnected form breaker box. My first clue that something had happened was several items plugged into the wrong outlets.
An investigation showed all the dead outlets were shorted. A look inside the breaker box confirmed that the wires had been disconnected.
Questioning the caretaker, I found out about one of the outside outlets had been smoking. I could well believe this, as the whole circuit was a dead short. So I set out to identify the problem and try to repair it.
Not a particularly difficult task, except the electrical code and construction is somewhat different here in the Philippines, than what I was used to back in the US.
Basic Theory
So let us start with some basic electrical theory. First up is Ohm’s Law, which states that the voltage is equal to the current times the resistance (E=IR). Next, we are dealing with Alternating Current (or AC). And the voltage in the Philippines is 220 to 240 VAC, not the 110 VAC we use in the US.
According to Ohms law, if we have zero resistance (a short), and 230 VAC, we would need infinite current (I = E/R with R being zero, one of those divide by zero conundrums). Since the breaker is has a current ratting, it should, in theory, trip.
Troubleshooting
This is a two wire system, common and hot leads, no ground wire (probably a good place to think about installing a GFCI). Since the wires are disconnected in the Breaker box, and nothing is plugged into the outlets, the resistance across the two prongs should be the total circuit resistance.
Before doing anything else, I set my meter for Volts AC and measure across the outlets. The result was zero ohms, indicating no power, and the circuit is safe to work on.
After confirming no power, I switch to ohms on my multi meter, and measure the resistance. This turns out to be zero ohms.
The next step is to pick an outlet in the center, and disconnect one side, then measure the resistance on the two legs. The first leg, between the breaker box and the outlet reads infinite ohms (open), and the rest of the circuit reads zero ohms. This tells me that the problem is in the second half of the circuit.
Moving further down the line I finally isolate the problem to a shorted wire run between two outlets. This will require pulling new wires, which will be interesting as the conduit is under cement.
Conclusion
This was an example of using some basic electronic theory, and half stepping troubleshooting to isolate a problem.
An examination of the plugs showed signs of water intrusion. However in this case, since several outlets are near the garden areas, I thing it is sprayed water, and not rain, that caused the problem.
I have several next steps to perform when I get eh time. Fist, pull a new wire pair, second look for a better waterproof outdoor outlet box, and third investigate adding a GFCI outlet to the circuit.
Add New Comment