I recently solved a home heating issue. If you like messing with fixing your own house, there is a wealth of knowledge out there. The issue I was trying to solve involved our furnace and, ultimately, the furnace circuit breaker. A circuit breaker is a reusable electric fuse. They were invented in 1924. It breaks the circuit when a set amperage is exceeded. Runaway amperage tends to set things on fire, so each circuit in your home has one.
So why am I writing about this relatively benign experience of home ownership? Solving this issue as quickly as I did, as a novice, really drove home the value of well-understood and well-documented failure modes in a product. The circuit breaker has 99 years of field usage and failures under its belt. Now with the internet, it isn’t just the experts with this century of knowledge at their fingertips. YouTube is society’s great equalizer for knowledge, even if you don’t have the skills to apply it correctly. Which, in turn, is the source of so many great “fail videos.” With this acquired knowledge, I immediately knew what to look for once I had the symptoms and went through the recommended diagnosis steps.
Comprehensive knowledge of a product, its failure modes, and root causes comes one of two ways; either we have investigated and documented it in the design process using DfR, or we acquire that knowledge involuntarily over many years of field use. Our customers are the test engineers, and our field service team is now R&D, and no one is happy.
This specific circuit breaker failure mode would have been miserable to root cause in the field. There were no visible clues as to the failure mode. Worse off, everything looked new, appeared to function properly, and was deceptively simple in appearance with no visible wear.
What was the issue? Ultimately, a change in material properties in a bi-metal strip from years of thermal cycling caused the failure. This could have only been root caused by very specific bench testing derived from a specific hypothesis and access to the original material specifications. If the circuit breaker was new technology, and we were root causing this issue for the first time in field conditions, my house would still be freezing. So many new technology customers get left out in the cold (pun totally intended) when they trust us, and we don’t do DfR properly. I share more detail on the experience in this video.
-Adam