The second gremlin started attacking our phone system. At apparently random times, the breaker for the switch would trip. The switch just happened to be mounted on the same wall as our disconnect box. Aha! Just find where the water had leaked in. Nope, not the case in this scenario.
Two odd facts came to light. First, the breaker was in the main panel in the old section of the building, not the new panel in the new section. Second, just before the breaker tripped, the conduit leading to the panel (about 40 feet that we could see) would hum violently.
Time to call CE -- if the phones would stay up long enough. The breaker tripped again just before we hung up the phone. When the electrician got there, we started tracing the conduit.
Our first guess was that there was an exposed wire somewhere in the conduit. The conduit ended up going outside, where a weatherproof box and outlet was mounted about a foot above the ground next to the AC system. A new section of conduit had been added, which ran back inside the new section to power the phone switch.
It was only a few feet from the outlet box to the switch, so what could possibly go wrong? The electrician opened the outlet box -- it was full of water. The seal had probably been damaged when the new conduit was installed. When it rained, the conduit would fill up until it shorted the outlet. In the few seconds until the breaker tripped, some of the water would be boiled away, allowing the breaker to be reset. The electrician removed the outlet box and sealed up the connection.
This entry was submitted by Michael Blazer and edited by Rob Spiegel.
Michael Blazer served 12 years in the US Air Force in metrology. In the last six years, he was doing test and evaluation on electronic warfare test systems and was the tester for a new survival radio. He has worked as several different types of engineer, and now builds test stations for a living. For fun, he mentors a local BEST (Boosting Engineering, Science, and Technology) team, and helps to maintain all the electronics kits for the San Antonio BEST hub.
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.