ECN Forum Forums General Topics of the Trade General Discussion Area Toasty Fuse

These fuses are for one of two heat strips in an roof top air handler. This emptied the building by tripping the smoke detector in the unit. The center fuse failed and burned,scorching the fuses above and below. I checked the disconnect, wires,fuse block,and contactor points for signs of overheating and found nothing. All connections were tight. There are no shorts to ground on the heat strips or anywhere else in the circuit. I cleaned up the soot on the block contacts, installed new fuses and everything fired up ok with normal amp draws and no voltage drops. I've never had a fuse fail without being able to find the cause. Any thoughts or is this going to be one of those unexplainables?
[IMG]http://members.cox.net/jkochan23/Picture%20011.jpg[IMG]

IMG]http://members.cox.net/jkochan23/Picture%20016.jpg[IMG]

It definitely looks like the center fuse had overheated to failure and fire by the looks of the copper in the second photo. If the fuse clips look good I would imagine the fuse itself may have developed a high resistance connection at the fusible element itself.

-edited for lack of spelling/typing ability-

[This message has been edited by Crowbar (edited 01-04-2006).]

[This message has been edited by Crowbar (edited 01-04-2006).]

jkochan,
I've re-posted these pics in the Photo's Submitted for Discussion Area.

The new thread can be found here .

{Message edited to add link}

[This message has been edited by Trumpy (edited 01-04-2006).]