Does your 10 year warranty actually cover things like this or is it more along the lines of 'major structural defects' which is pretty common/mandated in some areas?
Doesn't the contractor get a chance to 'make it right' or at least get a chance to look at the problem before you hire someone else to make repairs? I am in the camp that the connection was a slightly loose and enough heat cycles made it worse - but how long do you really expect something like that to be warrantied for?
I highly doubt that the warranty covers this.....I believe the builders warranty covers major structural: foundation, integrity of load-bearing walls, etc. I also believe that the short term component of the builders warranty covers certain things within the first year or two - things that are expected to last more than a year. Those items would include a vent fan in a bathroom, the garbage disposal, a window lock, etc. What's generally not covered? Things like settling resulting in minor exterior cracks in the stucco.
There's a difference between something failing and something being done improperly. In this case, the component parts failed because they were installed incorrectly. Each part has a proper use somewhere, but not in this combination. Furthermore, there's no user interaction with a 4.5" x 4.5" box that would cue anyone to its deficiency until it catastrophically fails.
Had the connections been secure, it's possible that this improperly done work would never have been discovered. I agree with that.....Let's say you're not mechanically inclined, and I build and sell you a car. When building this car I make the brake lines out of aluminum and use single flares throughout. Let's say that it somehow holds together. Six years down the road, out of warranty and having otherwise functioned without failing, one of those lines lets go. Am I not liable? Particularly if it can be easily demonstrated that I knew or should have known better?
I don't expect them to warrant or cover a light switch or breaker - something that a reasonable person can be expected to interact with. They hid this behind a cover that Joe Homeowner would never have any reason to open up. And it "functioned" up until the deficiencies - a loose connection and no room in the box - combined to cause this. Even though we recognize that this 4.5" x 4.5" box was acting as a "pull box" and perhaps was intended as a holding point for work to be done the next week, it nonetheless ended up being used as a box, and as a box the fill requirements weren't met. What is the point of the fill requirements? When I google the basic question of why we have box fill limits, I get answers such as this:
"....a box that is overfilled can cause a fault, arcing, or even a fire." Of course the companies that did this work would point out that this admonishment cautions against a possibility, and that the actual causation was just the arcing, since we can't prove the box was smoldering for all of the previous 6 years.
These kinds of questions are answered by fire investigators and forensics, none of which will be utilized here because its just not worth it. In this case, Joe Homeowner stood out there, looked at the equipment pad and the wall and thought, "No way. There's no way someone would do that." Four screws later he found that they did.....There's no way in hell these ***-clowns get a second shot. I'll eat every penny and move on before that happens. You don't get a chance to right an intentional wrong; you get a chance to right a mistake. Big difference here.
I'm a reasonable person. My assumption is that someone at these companies will be very disappointed to see that one of their guys did this. My assumption is that they'll want to make it right. My assumptions are sometimes wrong....