When Does a Fuse Catch on Fire?
When Does a Fuse Catch on Fire?
(OP)
We had an electrical fire in a heater controller enclosure today, where a 5 Amp fuse was disintegrated!
The 5 Amp fuse was in a block of 4 fuses, from left to right >>20A>>20A>>5A>>5A. The 3rd fuse from the left.
No breaker was tripped. The fuse just isn't there any more; it's all carbon charred dust, with black soot all inside the enclosure. No other wires melted; all insulation appears to be intact.
What could cause this?
And, here are the details, if it helps. 5A fuse is protecting a transformer from which drops a 480VAC down to 110VAC. The 20A fuses are for the heater elements. The heaters are 480VAC 8KW. The heater controller is a 110V PID controller from Omega. Very simple operation.
The main question again; what could cause a fuse to burst into flame? Underrated or overrated?
The 5 Amp fuse was in a block of 4 fuses, from left to right >>20A>>20A>>5A>>5A. The 3rd fuse from the left.
No breaker was tripped. The fuse just isn't there any more; it's all carbon charred dust, with black soot all inside the enclosure. No other wires melted; all insulation appears to be intact.
What could cause this?
And, here are the details, if it helps. 5A fuse is protecting a transformer from which drops a 480VAC down to 110VAC. The 20A fuses are for the heater elements. The heaters are 480VAC 8KW. The heater controller is a 110V PID controller from Omega. Very simple operation.
The main question again; what could cause a fuse to burst into flame? Underrated or overrated?





RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
Can anyone else confirm?
Thanks
RE: When Does a Fuse Catch on Fire?
Wheels within wheels / In a spiral array
A pattern so grand / And complex
Time after time / We lose sight of the way
Our causes can't see / Their effects.
RE: When Does a Fuse Catch on Fire?
If I only had a dollar for every time I was told they didn't do anything wrong!
RE: When Does a Fuse Catch on Fire?
analogkid2digitalman is correct in that this is usually caused by looseness which means it could be the actual connection of the wires to the fuse block too, not just the fuse.
That said... A 250VAC fuse jammed into 480VAC service is sure to toast during a fuse blowing fault event.
RE: When Does a Fuse Catch on Fire?
What is the current condition of the transformer?
e.g. if it developed a hard short that drew a high (peak) short circuit current, then a sustained plasma arc inside the fuse could have developed.
Have seen a 120V AC fuse (and fuse holder) blown completely out of a radio that took a direct antenna lightning strike.
Antenna lightning arrestors were installed (but old arc gap technology and, NO bonding from antenna ground to power service entrance ground, so the subsequent ground shift from the lightning hit just ate it up..
RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
Wheels within wheels / In a spiral array
A pattern so grand / And complex
Time after time / We lose sight of the way
Our causes can't see / Their effects.
RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
Somewhere I posted a link to the BEAMA website, but the search function won't find it. Here it is again:
ht
The following excerpt is really concerning:
Beware of products that are too good to be true. They are probably from China!
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If we learn from our mistakes,
I'm getting a great education!
RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
So that the screw terminal may well be nice & tight to start with, but the tin tends to flow away from the pressure and the whole thing loosens up.
Same thing applies to crimp terminals.
And rewireable mains plugs.
For all these things it's best to cut off any soldered ends and crimp /screw down onto the bare copper conductor.
rgds
Zeit.
RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
RE: When Does a Fuse Catch on Fire?
They won't stop overheating due to loose connections.