Old house, 100A fusebox, should we replace w. breakers?

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DonL

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JW is correct that fuses will blow quicker than Breakers of the same size.

I do believe fuses are safer. But keeping spares is a smart thing to do.

Most home style breakers contain a heating element and a bimetallic Cutout, Heat makes them open.

The breaker may take a dead short or UP TO 10X rated Value to trip Immediately.
The surge current of normally operating devices (Mostly Motors) is the reason that breakers have delays built in.

Normally they will trip at there rated current in Milliseconds (MS). Could be many, depending on the load.


If it was very many seconds, the Fire could have already started, and that would defeat its purpose.



I disagree with that link as it states.

"A fuse might make the difference if you get hit with lightning."

I Fuse can not protect from a direct hit from lightning. It will jump across it.

A gas discharge tube connected to a good ground maybe, but not a fuse of any type can fool Mother Nature.

Making sure the current flows into the ground, instead of your equipment is the key.
 
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DonL

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We have plenty of spares, tho some are rather old.
Maybe we will stick with what we have.

Not a bad choice, You may want to Pick up more spares when you go to the big town.

Old is good, If it is working.

They are getting harder to find.
 

DonL

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I lived in a house many years ago and the wires ran parallel on insulators.

It was cool to see real time old school.

That was back before a ground was ever ran to any outlets.

The wire had Cloth insulation, I guess Grandma made it. lol
 

JWelectric

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While teaching at DCC we did a test using a GE 20 amp breaker and a very large rheostat. We loaded the breaker to 30 amps for over two minutes before it opened. We loaded the same breaker to 120 amps and it took just under 10 seconds but over 9 seconds to open. (The watch had 10.2 seconds but we subtracted the reaction time to operate the stop watch)

We did the same test using Square “D” home line and Siemens breaker with similar results.



I need to make some corrections. I talked with Tommy today about our experiment. Tommy was one of my students who has done nothing but go forward in the electrical profession. He remembers the experiment and kept his notes to wit I need to make some corrections.

The max load was 100 amps not 120. We also determined that there was a plus or minus 15% in the ammeter that was being used also. The meter was out of an old control panel and wasn’t completely accurate. The GE breaker fared better during the testing than the other two with the Square “D” taking the longest to open.

We also used a NON-20 amp fuse that opened faster than he would work the button on the stop watch with the old pot set at the same resistance for the 30 amp test on the three breakers. It opened faster than the old ammeter would and we never got a reading on the amperage so for the sake of the experiment assumed it to be a 30 amp load as it was the same setting for 30 amps for the breakers although the connection was made a little different.

Please forgive my mistake as my memory is not as good as it once was and this test was done in September of 2002.
 

DonL

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I need to make some corrections. I talked with Tommy today about our experiment. Tommy was one of my students who has done nothing but go forward in the electrical profession. He remembers the experiment and kept his notes to wit I need to make some corrections.

The max load was 100 amps not 120. We also determined that there was a plus or minus 15% in the ammeter that was being used also. The meter was out of an old control panel and wasn’t completely accurate. The GE breaker fared better during the testing than the other two with the Square “D” taking the longest to open.

We also used a NON-20 amp fuse that opened faster than he would work the button on the stop watch with the old pot set at the same resistance for the 30 amp test on the three breakers. It opened faster than the old ammeter would and we never got a reading on the amperage so for the sake of the experiment assumed it to be a 30 amp load as it was the same setting for 30 amps for the breakers although the connection was made a little different.

Please forgive my mistake as my memory is not as good as it once was and this test was done in September of 2002.


Got to love them students JW.

They don't have the CRS yet.

I do not rely on my memory because I ran out 1 Megabyte ago.

I bet the students really enjoyed you as a teacher.


Good teachers are hard to come by, and they will remember You Forever and a Day...


You are the best.
 

capecod

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We are open to these options, just want to do a bit more thinking and studying.
Thats why Im so glad we found this forum, very educational.
 

ESCO

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People are afraid of fuses but they do open circuits [ disconnect] faster than most breakers
But you are right they are less user friendly
 

capecod

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I sure appreciate all this information, and I now agree with you all and my husband, the fuse box will stay.
We have plenty of fuses and managed to find a replacement for the big main knife fuse, used but in perfect shape, from a local electrician.
Thank you!
Jane
 

BobL43

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Got to love them students JW.

They don't have the CRS yet.

I do not rely on my memory because I ran out 1 Megabyte ago.

I bet the students really enjoyed you as a teacher.


Good teachers are hard to come by, and they will remember You Forever and a Day...


You are the best.
Stir, stir, stir sir
 
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