Overheated Fuse - ECN Electrical Forums

Thanks to Johno12345 for the following:

Quote

This fuse and holder was removed from one of our oil quench cooling systems which had stopped working. There seem to be 3 things wrong that may have caused the heating. The terminal screw was loose, the fuse screws were both loose and there seems to be some spring contacts misssing from the burnt side. The fact that the load cycles probably accelerated the demise of this. The fuse is still in tact. Incidentally, does anyone know the relevance of the "RED SPOT" on the fuse?

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

If I'm not mistaken, the red spot blackens when the fuse blows.

Littlefuse makes fuses (called "The Indicator") with a small window so you can see part of the element inside. If the window is blackened, it usually means a dead short occured vs. an overload.

Is that a tensile-test piece on the desk? Takes me back a few decades!

Alan

That looks like a lot of strands for such a small conductor size???
If it is not the standard number of strands for the conductor size, it may not be a Class B stranding type, which most likely would not be permitted in this type of installation.

Curious, what is that PC-board memory module like thingy on the desk, beside the little screw?

PCM-CIA board?

That does look like the sort of stranding one sees on welding cable or the conductors in SO cord. What are the issues with using this sort of stranding?

-Jon

Are those ribbons wrapped around your shoes?

Red Spot is a brand-name.
That wire looks not unlike welding cable, with that many strands in it.

Hi,

Sorry for the delay in responding - I forgot my password [Linked Image]

I thought the red spot might indicate the status of the fuse by some sort of heat sensitive ink. We have some fuses with the windows and of course the BS3036 rewirables!

That is an Elevated Temperature 10mm dia tensile from our test lab.
I am not sure of the cable size or type but it might be SY cable, I will ask tomorow.

that memory board is a Postage Rate PROM, some of you might know that UK postage has increased from Monday and that tells the scales how much postage to charge to the franking machine.

Those are not ribbons, they are laces, 2 pairs is the style [Linked Image]

they are Osiris D3 2001.

I have found the Red Spot company and all of their fuseholders have 2 red spots!

These fuses are pretty common here.
As are the holders.
GEC HRC fuses are taking over from them though in the higher amperages.
Red-Spot is a trademark of English Electric BTW.
I would have thought that a few of your UK guys would have known that. [Linked Image]

There is one thing that I personally hate about this particular fuse carrier design and it shows that it was designed by a draughtsman, not an Electrician.
That being, try and pull one of them fuses with rubber inners and leather outers on your hands, it's not possible!.
GEC had the good idea of putting a secondary pulling flange on the fuse carrier, in all sizes from 32A upwards.
GEC is the preferred fuse-holder of our PoCo.

{Edit: Under our current Standards here, if you withdraw a fuse, the live contacts shall be shrouded, while the fuse is withdrawn, a few types of fuse-holders here were withdrawn from sale because of that fact.}

[This message has been edited by Trumpy (edited 04-06-2006).]

I have been reliably informed that the cable is/was tri-rated cable for additional flexibility, this fuse is mounted inside a 6foot square cabinet which regularly catched fire here and there, the whole kit is connected to 250A parallel breakers (surely a violation in its self!) makinig 500A