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#19087 - 12/19/02 03:40 PM Parallel Fuses?????
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6805
Loc: Brick, NJ USA
Did a property survey yesterday for 50KSF retail store, 2 story, partial basement, +/- 60 years old.
Opened one main disc, tag states 800 amp, 250 volt, 3 phase, 4 wire.....
It has 2-400 amp fuses per leg.....????

The second disc; 400 amp, 250 volt, 3 phase, 4 wire has 2-200 amp fuses per leg...???

THe line and load are both buss....
The discs were made by Federal, and the rest of the discs are "Empire"; all fused pull-outs from 100 to 400 amp.

My questions
Was parallel fusing ever "legal"??
(Must have been at one time, as NJ has had inspections for a long, long time)
Is this an actual 800 and 400 amp feeder??

Also, anyone ever seen a CB panel rated 187 amps??? (42 circuit & 36 circuit, 3 phase, 4 wire, "Empire" brand,1940-1950 vintage)

PS: None of the above are autographed by Thomas Edison!

John
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#19088 - 12/19/02 04:15 PM Re: Parallel Fuses?????
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
 Quote:
autographed by Thomas Edison!



oh but if they were John......

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#19089 - 12/19/02 05:00 PM Re: Parallel Fuses?????
Nick Offline
Member

Registered: 08/13/01
Posts: 603
Loc: Riverside, CA
Were the fuses physically attached or in separate clips? I have never seen it in <600 V but paralleling the barrels in one clip is quite common for obtaining higher AIC ratings in Medium Voltage applications.

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#19090 - 12/20/02 12:34 PM Re: Parallel Fuses?????
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6805
Loc: Brick, NJ USA
Further info:
On each phase, there is one knife; there are two (2) fuses for each phase; they are next to each other in individual clips (holders).

Sparky:
Yes, if only the autograph was "real".

I have pictures of the discs, and I guess I'll spend some time this weekend trying to figure out how to send them in.....

John
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John

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#19091 - 12/20/02 12:49 PM Re: Parallel Fuses?????
DHeath Offline
Junior Member

Registered: 06/19/02
Posts: 2
Loc: Plainville, CT USA
Prior to about 1970, safety switches (per UL Std 98) above 600A did have (2) parallel fuses. I don't think it was permitted for 600A and below.

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#19092 - 12/20/02 01:00 PM Re: Parallel Fuses?????
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6805
Loc: Brick, NJ USA
Dheath:
If the fuses are paralleled...do you have 800 amp???
John
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#19093 - 12/20/02 01:09 PM Re: Parallel Fuses?????
DHeath Offline
Junior Member

Registered: 06/19/02
Posts: 2
Loc: Plainville, CT USA
Yes, but continuous load can't exceed 80% of paralled fuse rating (i.e., 800 x .8 = 640A max cont. load.)

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#19094 - 12/21/02 09:33 PM Re: Parallel Fuses?????
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Parallel Fusing sounds dangerous,
I've come across this a number of times,
especially where the fact is not marked.
Causes a bit of confusion, if you are trying to Isolate a circuit, it's almost like a Ring Circuit, but it's not!.
Pull one fuse, the voltage drops to 220 odd volts, pull another, nothing changes, try and find the other leg of the circuit.
This sort of wiring, should be outlawed!
Especially where Poly-Phase circuits are concerned.
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