- Joined Oct 3, 2010
I just had a bunch of wires melt in a control panel because a fuse didn't blow. It was a TR5R (5A time delay fuse) that was "protecting" a phase angle fired SCR heater controller. The heater had shorted out. I'm thinking that for those 14AWG wires to melt, they had to have well over 20A flowing through them for an appreciable amount of time. According to the TR5R data sheet, the fuse should have blown in <1 second if it had 20A flowing through it. the best I can come up with is that the fuse didn't see high enough current for long enough due to the "long" delay between AC cycles due to the phase angle firing. I don't have a lot of faith in this explanation, but like i said, I got nothing better. Any ideas?