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Re: Fuse failure #20689 01/21/03 03:32 AM
Joined: Jan 2003
Posts: 53
Len_B Offline
Could just be bad fuse

[This message has been edited by Len_B (edited 01-22-2003).]

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Re: Fuse failure #20690 01/21/03 07:08 AM
Joined: May 2001
Posts: 30
Nevin Offline OP
No that is not the photo. The fuses are all three FRS-R fuses. The connections were all sound. The replies in the first three posts seem to me to be the most likely reasons. Although I'm not quite sure why the spring clips would have lost their tension unless it was progressing to that point over the last few years or months and finally simply became to weak. I am putting those clip clamps on as resqcapt19 suggested.
I guess here's a prime example of where thermographic imaging could have caught the problem early on before it failed.

Re: Fuse failure #20691 01/21/03 01:25 PM
Joined: Jan 2003
Posts: 134
lighthouse Offline
Nevin...i have a question

what size horsepower motor is on the air it a 25 hp ? we know by the fuses it"s 460 or 480 volts.right?

Re: Fuse failure #20692 01/21/03 02:43 PM
Joined: Sep 2002
Posts: 83
Pearlfish Offline
I apologise guys.

My eyes crossed columns when I looked in the catalog. Thanks for catching my error.

Re: Fuse failure #20693 01/21/03 06:11 PM
Joined: Apr 2002
Posts: 2,527
Bjarney Offline
On "...why the spring clips would have lost their tension..."

This usually happens over a long time interval. The metal loses spring tension by softening through the annealing process.

Re: Fuse failure #20694 01/21/03 07:30 PM
Joined: May 2001
Posts: 30
Nevin Offline OP
Yes it is a 25 hp motor. it is an older one. Not a newer motor with the better energy efficency. I will have to look again on the motor for all the Specs.

Re: Fuse failure #20695 01/22/03 12:08 AM
Joined: Jan 2003
Posts: 134
lighthouse Offline
Nevin. you need to put in the 60 amp fuses per code.sizing motors,wiring, overloads, breakers or fuses is a gray area for a lot of electricians,even me years ago.but it not that hard.take the hp of the motor and check the code book 430-150 3 phase go down to 25 over to the voltage 460 it says 34 go to 430-152 time delay fuses it says 175% so now 34 x 175 = 59.5 amps.code 430-52 allows you to go up to the next standard size fuse or breaker look in 240-6. put in the 60 amp fuses [Linked Image]

an here one to think about. if you were to use one time fuses 34x300%=102 amps,you would go up to a 110 fuse and all on that # 8 wire.

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