Oddball Fuses - ECN Electrical Forums

Rewired has been exploring again [Linked Image]

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I happened to stumble on this in the girlfriends apartment building(s).
The " 550" and " 575" amp fuses are in the main disconnect of two of the buildings, the " 380" amp fuses are in a third building which actually has TWO main services, one for the units, one (225 amp main breaker) for the house load and now disconnected electric hot water tanks. ( all had electric hot water at one time, only the other buildings brought in a 100A gooV 3 phase service for the tanks, all of which is now disconnected..

I found a couple good violations that I will post later

Individual runs of copper water pipe? That's crazy!

Those also look like custom made fuses. It looks like the ratings were probably hand stamped on them. Those are pretty cool, so long as theyre used properly

Don't think that's water pipe, but a metal-encased, mineral powder filled (as insulation) cable. I forget the tradename, but there was a thread about it on here somewhere....

Pyrotenax. [Linked Image]

In the NEC it is called MI Cable.

It is fireproof (more or less) it can operate even while sections of it are exposed to open flame.

A typical use of it is for life safety emergency circuits.

The insulation between the copper conductor and the copper sheath looks like Sheetrock and is somewhat flexible until exposed to high heat than I believe it turns hard more like ceramic.

or MIMS

Mineral Insulated Metal Sheethed

Just an off the wall question but do you think they used this type of conductor because it basically runs unfused from the service head ( between the 2nd and 3rd floors) down to the sub basement where the disconnect is located... I assume they would have to have buried it in the masonry and concrete slab for protection?!?!
Doesnt seem correct, but thats how it was done 40+ odd years ago.

A.D

Here is the thread where MI (pyro) cable was discussed. [Linked Image]

{Message edited to fix tag}

[This message has been edited by Trumpy (edited 08-21-2006).]

Very cool! I will be definately looking up more information on pyro cables. That is the first time I have actually seen it installed and in service. Too bad its not too popular here any more, I would have really liked to get lessons on how to properly install pyro and get some hands on experience installing the stuff.

A.D

It looks like the lock nuts on the MI connectors are ferrous. That could be a problem. It apprears that the 3 MI connectors enter the enclosure via some type of plate that is bolted to the inside of the enclosure. I assume that is nonferrous to pevent induction heating.
Don

Don, they look like copper or brass to me.

Aluminum locknuts possibly? Seen those before when i worked behind the counter. Damn I will have to go down to the basement again and look! [Linked Image]

A.D

Do you think it pops at 576 amps?

LOL
Possibly!
We will never know because
"Murphy's law" happened there a few years ago.. A "$1500" Pole top transformer burned up in order to protect a pair of "$15" fuses..
Isn't that how it goes sometime days!!

A.D

I rewired a house once and found a whole lot of MI cable had been used throughout. It was weird finding it in a house. Its all gone now....