20 Amp Fuse in Place of 15 Amp & House Wiring

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  #1  
Old 04-02-13, 11:49 PM
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20 Amp Fuse in Place of 15 Amp & House Wiring

I just realized the previous owner of the house installed a 20 amp fuse where there should have been a 15 amp. My guess is that this occurred 14 or more years ago.

One outlet on the circuit recently partially melted the plug around one of the prongs of a 14AWG circuit breaker/surge bar. It also slightly melted the plug around one of the prongs of the washing machine, but I don't know how long ago. Neither of these items were ever plugged in at the same time.

This particular circuit has run a handful of high amp items such as: microwave, toaster, coffee-maker, washing machine, refrigerator (although rarely, if never all at the same time) for in the many years while the 20 amp fuse was installed.

I switched the fuse back to a 15 amp, and I'm replacing the outlet. (The outlet is probably at least 50 or more years old).

My questions are:

After 14 years or more of there being a wrong rating fuse in the panel, would it have had any adverse affects on the wiring between the fuse box & the outlet, or anywhere else in the particular circuit?

Is there a way to test for damaged wires in a home?
 
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Old 04-03-13, 12:19 AM
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Welcome to the forums.

It's possible that since the circuit could have been run with a heavier load on it...... that the insulation on the wiring could be a little tougher/harder. I couldn't see it being an issue to worry about. There really is no way to test it but you are fusing at 15 amps now.... so the circuit is protected.

Receptacles are usually ignored. On heavy draw appliances and especially those with heating elements..... the receptacle needs to be in good condition. The contacts must grip the prongs of the plug tightly. If not......resistance goes up, voltage transfer is reduced and heat builds up fast.

I've seen people use chairs, bookcases and other flammable objects to keep plugs in place

People wonder why there are electrical fires.
 
  #3  
Old 04-04-13, 10:15 PM
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While replacing the receptacle, I checked the wires in the outlet box & noted that the feed wiring is 12 gauge, and wiring that was used to branch off to a small room appeared less thick, as if it were 14 gauge.

The wires all looked fine. But in back of the outlet box where one black 12 gauge wire resting against the sharp edge of a screw, I could see discoloration on the back wall of the outlet as if there may have been arcing or something started to burn. After disconnecting the old receptacle, I pulled that wire towards me & could see the insulation was gone where it had rested against the screw edge, and the bare wire was exposed.

I don't know how long ago this condition manifested. I'm told the last time the outlet was touched was 45 years ago when the small room outlets were installed. So, I'm guessing this condition just developed recently. But, I don't know if the condition that caused the melted plugs led to this damaged wire, or if the damaged wire led to the melted plugs.
 
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Old 04-04-13, 10:37 PM
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Melted plugs occur when the outlet is worn out. The contacts get weak and don't grip the plug and things heat up and melt.

That was a 12 gauge 20 amp circuit but now that # 14 was incorrectly introduced......the circuit must not be fused higher than 15 amps.

There is a chance that the wire shorted to the box at one time. It probably blew a fuse and maybe at that time they put the 20 amp fuse in.
 
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Old 04-05-13, 02:36 PM
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If the wire was still shorted to the box the 20A fuse should have blown too.
 
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Old 04-06-13, 08:35 PM
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If the wire was still shorted to the box the 20A fuse should have blown too.

The 20 amp fuse never blew. Even before I worked on the receptacle, I switched to a 15 amp fuse & that didn't blow either.
 
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Old 04-06-13, 09:43 PM
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Even before I worked on the receptacle, I switched to a 15 amp fuse & that didn't blow either.
Hmmmm. Then someone fixed the short.
 
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Old 04-10-13, 11:15 PM
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No.... After my plug melted, I found there was a 20 amp fuse in place of a 15. So, I replaced the fuse with the correct size.

After this, I decided to replace the receptacle. I pulled the cover off the receptacle & noticed charring at the back of the outlet. I found a hot wire with a bare spot where it had been against the sharp edge of a screw where the charring on the back of the outlet was. I cut that bad part of the wire away & hooked up a new receptacle.

Neither the 20 amp or 15 amp fuse ever blew in recent history (several years). The bare spot of the hot wire was just resting against the sharp edge of the screw at the back of the outlet box. It wasn't repaired until I replaced the receptacle. Had I not replaced the receptacle, that wire would still be touching the screw.

To put it simply, there was a period of time when there was a fuse in the box that didn't blow while the wire was contacting the back of the outlet box.
 
  #9  
Old 04-10-13, 11:27 PM
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To put it simply, there was a period of time when there was a fuse in the box that didn't blow while the wire was contacting the back of the outlet box.
That could only be possible if the box was ungrounded. If the box was grounded.... a hot wire could not stay in contact with it. The fuse/breaker would blow instantly.
 
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Old 04-11-13, 11:29 AM
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The bare spot of the hot wire was just resting against the sharp edge of the screw at the back of the outlet box.
Is that a plastic box mounted with screws to wooden framing?
 
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Old 04-13-13, 04:54 AM
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Metal box. It's in the basement mounted on a cinder-block wall. There's plaster covering the wall, so I don't know if there is wooden frame or not. The screw hole in the second pic looks like wood, unless it's some 50 year old screw anchor.

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In pic below, the bare spot of the wire is visible.
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  #12  
Old 04-13-13, 10:40 AM
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Curiouser and curiouser.

Yes that certainly appears the be arc flash residue at the screw hole, and the damage to both the screw head and the hot wire are impressive. Yes, that does look like wood that the screw wad driven into and you say it's a masonry wall, so there doesn't appear to be any conductive material there, but that's normal.

This, BTW, is a very clear example of why electricians do not use flat-head screws, with their sharp edge, inside electrical boxes.

What's really interesting is that this appears to be the end-of-line outlet on a circuit with a grounding conductor, and that conductor, judging from the loop at the end of it, appears to have been connected to the grounding terminal on a 3-slot receptacle.

Here's a guess at what has happened here: It appears that the metal box was bonded to ground when the arc occurred. Otherwise there would not have been a complete circuit for the power to follow. It also appears that that complete path was lost after that, because the receptacle, and the circuit, functioned for a number of years after the initial fault.

Do you have a multimeter. Preferably an analog one, but a decent-quality one will do. Can you, or have you, checked the voltage from hot to neutral, from hot to ground, and from neutral to ground in this outlet (the box and the wires in it, not the receptacle)?

You should see 120V, 120V and ~0V, respectively. What you're testing for is a continuous path to ground. This test is not definitive of an adequate path, but it is indicative of whether there is still a path at all. Because it looks like you've lost that path somewhere up the line.
 
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Old 04-14-13, 01:39 AM
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Yes, I do have a multimeter, it's digital. I also have a Kill-a-Watt, and one of those 3-prong plugs that light up to tell you if the outlet is grounded. That's about it. Most of my other stuff is for automobiles.

You wrote: What's really interesting is that this appears to be the end-of-line outlet on a circuit with a grounding conductor, and that conductor, judging from the loop at the end of it, appears to have been connected to the grounding terminal on a 3-slot receptacle.

This outlet is a lone one in the basement. The rest in the circuit goes upstairs to the kitchen. There is a branch off this one to a small room in the basement to two outlets that haven't been used in many years. The 'grounding conductor', was connected to the ground terminal on the 3-slot receptacle. There's also a second ground wire that was also hooked to the ground terminal on the 3-slot receptacle. That ground wire runs to the small room outlets I imagine.

What do you mean by: It also appears that the complete path was lost after that

And.... How do I go about checking for these voltages (i.e. which probe goes where)?

There's something else I noticed about this circuit & I'm posting some pics of it. I noticed the initial incorrect 20-amp fuse had discolorations on it's base connector. Like-wise the new 15-amp that I had recently put in now also has such marks. Discoloration appears also in the fuse box where this fuse goes in. I checked another fuse on a different circuit & the fuse base & the fuse box connection is spotless.

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  #14  
Old 04-14-13, 07:03 AM
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I noticed the initial incorrect 20-amp fuse had discolorations on it's base connector. Like-wise the new 15-amp that I had recently put in now also has such marks. Discoloration appears also in the fuse box where this fuse goes in.
Those discolorations are actually signs of series arcing that occurred between the fuse and base of the fuse's socket. It's not that uncommon in 50 year old fuse boxes, but it does indicate there wasn't a tight connection between the fuse and the contact at the bottom of the socket.
 
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Old 04-14-13, 11:51 AM
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What do you mean by: It also appears that the complete path was lost after that
If the hot conductor remained in contact with the metal box and the box was bonded to ground, no fuse should have held. Since the receptacle continued to function while that fault was present, the most reasonable explanation is that the other half of the circuit, the path to ground, was somehow lost.

How do I go about checking for these voltages (i.e. which probe goes where)?
Originally Posted by Nashkat1
Can you, or have you, checked the voltage from hot to neutral, from hot to ground, and from neutral to ground in this outlet (the box and the wires in it, not the receptacle)?

You should see 120V, 120V and ~0V, respectively. What you're testing for is a continuous path to ground.
That is, from black to white, from black to bare and from white to bare, with all wires disconnected and separated, on the wires in the cable bringing power from the panel.

This outlet is a lone one in the basement. The rest in the circuit goes upstairs to the kitchen.
What does it power in the kitchen? Are any of your small appliance (countertop) branch circuit receptacles on this circuit?

There's also a second ground wire that was also hooked to the ground terminal on the 3-slot receptacle.
The wires for each phase - hot, neutral and ground - should be spliced together in this box. A third piece of wire, the same color and gauge as the wires in the cable and about 8" long, should be added to each of those splices as a pigtail. The pigtails should be connected to the appropriate terminals on the receptacle and all terminal screws tightened down, whether they have a wire attached or not.

In addition, this metal box needs to be solidly bonded to ground. That can be done by adding a second pigtail to the ground wire splice or by making that pigtail longer than the others, and using either a ground screw or a ground clip to connect it to the box.
 
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Old 04-17-13, 04:43 AM
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What does it power in the kitchen? Are any of your small appliance (countertop) branch circuit receptacles on this circuit?


This lone outlet in the basement is what the washer runs off of.

Aside from this lone outlet, there is a branch off to a small room that has two outlets (rarely ever used).

Upstairs, there are four outlets in the kitchen. It powers the fridge continuously. Other items on the circuit are the toaster, coffee maker, & microwave.

It's always been a rule to never use the microwave at the same time as the toaster or when the coffee maker is making coffee, and to never use all three at the same time, or any when the washer is running.
 
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Old 04-17-13, 09:57 AM
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This lone outlet in the basement is what the washer runs off of.

Aside from this lone outlet, there is a branch off to a small room that has two outlets (rarely ever used).

Upstairs, there are four outlets in the kitchen. It powers the fridge continuously. Other items on the circuit are the toaster, coffee maker, & microwave.
It sounds like three of those receptacles in the kitchen are countertop receptacles. If so, they need to be on a 20A circuit that only serves them, and has GFCI protection. There should be two of those circuits. The receptacle for the refrigerator can be part of one of those circuits, but nothing is allowed outside the kitchen.

The washing machine also needs a 20A circuit. If it is in your unfinished basement then it will need to be GFCI protected. The other two outlets in the basement may need to be separated from it.
 
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Old 04-18-13, 11:58 PM
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Back to the root issues here...

I need to check to make sure I have a 'continuous path to ground'. That, I haven't done just yet because I still don't understand how, and don't want to make the next episode of '1,000 Ways to Die'.

Also, it's apparent the fuse in the panel was either loose or didn't make good contact to the fuse socket base in the fuse panel, since there is evidence of arcing. Perhaps the socket base is not flush. I'm going to assume that they do not sell replacement parts for this fuse panel since it was popular in houses at the same time the 'Leave it to Beaver' was popular on TV.

I've got a book coming in that has pictures & may explain all about house wiring so I can understand it better. Hopefully I will be able to locate my aloof cousin who is a retired electrician. Maybe I can get him to come and look at things.

As for the initial problem....the circuit/surge bar with the melted plug is long in the trash. I did accomplish some other things: the old outlet is replaced, the damaged section of the hot wire was cut away, the wires are moved away from sharp screws & edges, the right amp fuse is tight in the panel.
 

Last edited by Mechanicus; 04-19-13 at 12:30 AM.
  #19  
Old 04-19-13, 05:18 AM
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My theory: The short in the recep box caused the 15-amp fuse to pop a couple of times so the previous owner put in a 20. By then the short had cleared itself, and there it remained until you discovered the issue.
 
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Old 04-19-13, 08:02 PM
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I need to check to make sure I have a 'continuous path to ground'. That, I haven't done just yet because I still don't understand how,
You see a ground wire in your cable. That's a start.

Back to basics 1: When you do the testing asked for earlier, if you find ~120V hot-to-neutral but you don't see the same thing hot-to-ground, then you don't have a continuous path to ground from that location. You'll need to create one, repair the one you have, or provide an alternate means of protection.

Back to basics 2:
Originally Posted by Nashkat1
It sounds like three of those receptacles in the kitchen are countertop receptacles. If so, they need to be on a 20A circuit that only serves them, and has GFCI protection. There should be two of those circuits. The receptacle for the refrigerator can be part of one of those circuits, but nothing is allowed outside the kitchen.

The washing machine also needs a 20A circuit. If it is in your unfinished basement then it will need to be GFCI protected. The other two outlets in the basement may need to be separated from it.
I've got a book coming in that has pictures & may explain all about house wiring so I can understand it better.
If that book is Wiring Simplified it just may be the best investment you'll make in getting up to speed on your electrical system. Two primary reasons: One, Wiring Simplified is constantly being updated to be in compliance with the most recently adopted NEC and, two, it explains why, as well as how, things are done the way they are. If it's some other book, all bets are off.
 
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