Glass fuses

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powerplay

Senior Member
I have come across an old industrial/commercial electricians home that was wired using relays for lighting and hydronic heating, as well as panels full of glass fuses. The idea was that breakers were unreliable. Aside from the inconvenience of finding a fuse replacement and parts, are there any insurance or other concerns that anyone know of regarding all the glass fuses or are they really that great? Thanks again!
 

Little Bill

Moderator
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Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
I have come across an old industrial/commercial electricians home that was wired using relays for lighting and hydronic heating, as well as panels full of glass fuses. The idea was that breakers were unreliable. Aside from the inconvenience of finding a fuse replacement and parts, are there any insurance or other concerns that anyone know of regarding all the glass fuses or are they really that great? Thanks again!

A lot of Ins. Co. around here won't insure a house with fuses. If the house is already covered they will continue to cover it but if the house sells, they will require the panel be upgraded to breakers before they will write a new policy. The reason being, a HO will replace a fuse with whatever size will go in the panel. Where as, most HOs don't know how or won't replace a breaker if it fails. Assuring proper OCP is their motive behind this.
 

Jraef

Moderator, OTD
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Location
San Francisco Bay Area, CA, USA
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Electrical Engineer
... The reason being, a HO will replace a fuse with whatever size will go in the panel. ...
Or worse yet, the penny behind the fuse trick. I bought an old Victorian house in Seattle that was built in 1889. When I put in a breaker panel, I yanked the old Edison base fuse box from when the house was electrified (it was originally built without wiring). I scored a 1909 Indian Head penny in great shape. Sold it at a coin shop for $150!
 

broadgage

Senior Member
Location
London, England
As others post, insurers may require the MCBs be used in place in of fuses to greatly reduce the risk of the wrong size OCPD being used.

Otherwise, no problem in useing fuses.
I would however be rather concerned at the use of glass fuses. Are these cylinderical glass cartridge fuses, with the fuse wire visable within ?
If so, they are probably unsuited to branch circuit protection, and pending any major upgrade, the glass fuses should be immediatly replaced with ones listed for the purpose.
Here in the UK glass fuses have only very low interupting ratings and can fail explosively if subjected to the fault currents likely to be found.
One brand has a maximum interupting rating of only 10 times the normal current, that is a 15 amp fuse can only safely interupt a fault current of 150 amps.
Other types are only intended for vehicle electrics and similar, not for line voltage.

Ceramic bodied fuses filled with sand or other materials have very much higher breaking capacities and are suitable for virtually any likely fault current.
 
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