Fuse blows immediately when replaced

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Posted by: from St.catharines
12/29/2016 at 12:04:03 PM

I am having an issue trying to determine why the fuse for the back bedroom keeps blowing.

I have an older home and yes it has aluminum wiring. I have removed all 6 outlets, switches and ceiling lights. The electrical boxes are all open and the bared wiring is out and separated but the fuse still blows. I measured the resistance of the wires, my black or power feed has 5 ohms resistance, the white or neutral wire shows ground. Do you think that the two are contacting each other?. I have looked in the fuse panel and all the wiring looks fine,no signs of over heating or arcing. Any suggestions? ,

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Date/Time12/29/2016 at 1:13:28 PM

The white wire is connected to ground in the panel what are you ohming the black wire to I would suggest that u find the start and the end of the CCT and then work your way from the panel and out.

Make sure all wire clamps are Loose not pinching the cable coming in.

If the fuse or breaker trips black wire have to be connected to either ground or neutral somewhere.

Is it a fuse or a breaker you have.

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Date/Time12/29/2016 at 1:16:48 PM

If you have made any connections at all in ceiling oct boxes, turn off all the light switches in that area and see if impedance is still 5 ohms.

Its common for homeowners to screw up connections where the switch legs do not carry a neutral.

If that doesn't help, call an electrician. AL wiring is dangerous to work on if not properly trained.

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Date/Time12/29/2016 at 1:17:11 PM

Another thing is make sure to have everything unplugged on that cct before doing your ohm or other tests anything plugged in will mess up your tests and a CCT will usually have around 12 items like plugs and lights on it switches don't counts.

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Date/Time12/29/2016 at 4:06:25 PM

Hello Stephen,

Unfortunately your readings don't really mean too much as other have stated; there are too many variables such as length of cable, connected loads, etc; and I am not sure what you are measuring between to get a reading of any sort regardless.

The question is really is the fuse melting or breaking into pieces? If it is melting then it is an overload, if it is breaking into pieces then it is a short circuit. It might be difficult to see if the fuse is blackened (which generally means that it has been shorted circuited), but not 100% of the time. If the glass is clear and you can see the element clearly then it is likely an overload.

I have done a lot of AL wire remediation and I can tell you that in almost all situations like this there is a loose connection that is causing a fault of some sort. The second most common is a hidden junction (usually with a mixture of CU and AL wire). The third most common is a damaged wire; either through lack of maintenance, something that happened during construction or by external elements such as rodents.

If you search the Trusted Pros site, there is an article that I wrote which talks about the most common issues with AL wire.


John Kuehnl-Cadwell

Master Electrician

Datawise Solutions Inc

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Marco from MCC Electric in Quispamsis
Date/Time12/29/2016 at 4:15:32 PM

The only thing I can suggest is to contact a qualified electrician and he will know what to look for.

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Date/Time12/29/2016 at 9:39:08 PM

What you need to do is inspect the wiring to rooms that border the back bedroom, and inspect the switches, receptacles and lighting outlets as previous done in back bedroom, if you have a meter you can check for a short which would be follow by a reading between the hot and neutral on receptacles or outlets. if no reading all is good.

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Robert from ElecTriLight Ltd. in Oakville
Date/Time12/30/2016 at 12:13:35 AM

There are so many things to look for when searching for short circuits and open wiring. Some companies carry wire tracers that can be helpful to find where wires are damaged but are also expensive, so these companies would charge a fair hourly rate, but it seems you wish to locate the problem cheaply and remedy yourself, which may be a bit outside of your knowledge.

You can ask yourself if any buried junctions or wiring changes have been made in the past 10 years and think from there. I have also found people adding hardwood flooring who use long nails can easily damage wires under floors, near baseboards, door frames or even hanging pictures can do it. In most cases our wires should be 1-1/4" from any surface, but fished wires within closed walls may be found directly below the surface. You should be able to isolate which cable is causing the dead short and start from there. Check junctions in lights and possibly even prior to the junction boxes you believe feed only that circuit. There is no reason why an electrician would not use a 14/3 wire and run split circuits in a nearby switch or receptacle box... best advice, call a LEC in to avoid a house fire and make sure you have at least 3 working smoke detectors that are newer than 10 years of age (lifespan).

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Date/Time12/31/2016 at 4:34:02 PM

Electrical is not a hobby. Sorry, you don't know what you are doing and should hire a good electrician.


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