100 AMP Fuse Blowing on Service Disconnect on One Phase

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  #1  
Old 12-08-13, 09:28 AM
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100 AMP Fuse Blowing on Service Disconnect on One Phase

Mid 1980's house recently started overloading the 100amp service disconnect fuse outside. First time all the lights flickered in parts of the house and everything went off that was on that phase. Electrician came out, was useless and replaced the two fuses (originals were 200amp, now 100amp) and problem reoccurred after a few days.

None of the breakers are tripping inside the garage on the breaker panel. Only the one side is affected there are two 100amp fuses, and as you can see from the photo, the rights side is getting hot. Initially everyone suspected an open short on the compressor, however I have that breaker turned off, and also have the service disconnect to the OFF position for the outside heat pump.

This morning the inside emergency heat was running, and she was using the stove at the same time and it went down again.

One time it was triggered by using a hair dryer as well.





Thanks in advance for your feedback.
 
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Old 12-08-13, 10:00 AM
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Welcome to the forums.

Time to call another electrician. You have several issues that need to be addressed.

On your home service there is only one phase. Single phase service. You lost one of your 240v legs.

I see an old disconnect pull out that looks like 100amps. Not sure why there were ever 200A fuses in there and if there were..... HOW did you blow one of them out ? With age the fuseholders become fatigued/loose. That may be the issue with the one fuse.

You've got electric heating (reheats), electric stove, probably electric hot water. You are pushing a 100A service to the edge.

You would be better off running the heatpump so that you could shut the reheat coils off.
 
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Old 12-08-13, 12:25 PM
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With age the fuseholders become fatigued/loose. That may be the issue with the one fuse.
Agree........OR........the service might be plain overloaded. A third possibility is a combination of both.
 
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Old 12-08-13, 03:55 PM
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You are well overdue for a service upgrade.
 
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Old 12-08-13, 07:18 PM
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It is not possible to install a 200 amp fuse in a 100 amp disconnect. It is possible to install a 100 amp fuse in a 200 amp disconnect using fuse adapters.

I would agree with Joe, there is a loose connection at the fuse, or where the wire terminates.
 
  #6  
Old 12-09-13, 07:26 AM
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It is not possible to install a 200 amp fuse in a 100 amp disconnect. It is possible to install a 100 amp fuse in a 200 amp disconnect using fuse adapters.
Actually, they used to make 200amp fuses back in the day. Now you can only by 100amp. See 25208 Old Stock Cooper Bussman FRN R 200 Time Delay Fuse 250V 200Amp | eBay
 
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Old 12-09-13, 07:34 AM
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You should still be able to get 200 amp fuses for that pullout.
 
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Old 12-09-13, 07:44 AM
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Speaking of pullout, someone told me this setup predates the house (1982) and is old. When we get this fixed, what should we ask for?
 
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Old 12-09-13, 08:02 AM
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You will have a new disconnect or service panel with a main breaker installed if you replace this.
 
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Old 12-09-13, 08:04 AM
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Actually, they used to make 200amp fuses back in the day. Now you can only by 100amp.
No, fuses are actually quite common and popular and readily obtainable from any supply house and 200 amp is a very popular size, but they are a bit rare in residential use. What you linked to on Ebay is someone selling new OLD stock, probably from a hardware store that closed. Fuses are very much alive and well.
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Speaking of pullout, someone told me this setup predates the house (1982) and is old. When we get this fixed, what should we ask for?
I'd go with breaker disconnects which are much more common in residential use, but you still need to have the total load and the entire service evaluated.
 
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Old 12-09-13, 04:31 PM
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Actually, they used to make 200amp fuses back in the day
My point was that a 200 amp fuse can not physically fit in a 100 amp disconnect, but a 100 amp fuse can fit in a 200 amp disconnect using fuse adapters. Therefore, if your disconnect outside is truly a 100 amp disconnect you could never had 200 amp ones installed. If there was, you then have a 200 amp disconnect.

As the others have pointed out 200 amp fuses are quite common and still used today.
 
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