I was troubleshooting a 480V heater in our paint shop. I was checking the fuse disconnect for voltage. Line side 277V to ground on all three phases. Line side A to B, A to C, B to C 480 V. Okay so the load side, 277 V on all three phases. Load side A to B 480V, A to C 0V, B to C 480V. So somethings not right, so I pulled the fuses out and I checked them. Fuse A was bad. So how did I get 277 V to ground??? Maybe somebody else has experienced this before. Thank you for your help.
Fuse blown, but still allowing current on the load side?!
- Thread starter zappy
- Start date
ptonsparky
Tom
- Occupation
- EC - retired
- Location
- Illinois
- Occupation
- retired electrician
When looking at fuses, read the voltage across the fuse. A voltage across the fuse indicates the fuse is open. That avoids the issue with reading back fed voltage from the connected load.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
That's what I do. A form of FOP testing.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
I have also done that with a test light. If it lights, the fuse is blown.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I use my K-60 for 99% of my troubleshooting.
Years ago, someone asked me what stops the current of the load from blowing up the tester.
I had to ask him what stops that from happening on a line-to-line test for it to dawn on him.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Yep. Get out of that habit.