How to Avoid Loose Electrical Wiring Connections
Electrical Troubleshooting Question:
I have replaced a good amount of receptacles in my home, and I'm the type of person that worries about every last thing possible and mainly about burning my house down. I know that loose connections are bad and very dangerous.
Wire around a Receptacle Screw Terminal
Whenever I loop a wire around a receptacle screw terminal I make the screw very tight to ensure and snug connection (as tight as I can with my screwdriver). What I want to know is if this will be okay. I have read somewhere that you can flatten the wire from over tightening the screw and create extreme heat. I just want to know if this will burn my house down, or if it is okay left alone.
We have not had any problems with any receptacles, and they are all cool to the touch. If you could get back to me with that answer, that would be great.
Thanks a lot. Matt.
Hi Matt - Great Electrical Repair Question!
First of all - would you PLEASE tell me where you found the information about tight screws. You are the second person to share this concern and it is false, especially when it comes to solid wire on an outlet screw terminal.
There may be a slim possibility of flattening a #14 wire down to the point of breaking the wire off, but I have never seen such a problem on an outlet. I have personally stripped out the screw a few times, and even broke the screws off when tightening down #12 solid wire on outlets. The only place I would advise caution would be inside the panel when tightening the mounting screws down on #14 solid wire where it attaches to circuit breakers and especially neutral and ground busses.
The mention of an overheating Tight Connection where the wire is flat is in my mind incorrect. Tight connections do not cause fires, loose connections do. Loose connections arc when the wire or circuit is under a load. I should point out that wiring outlets are typically done using two methods - Series and Parallel.
The Series method can create problems because the load of the whole circuit travels through each device, whereas using the parallel method this is not the case - only the load for each individual device is fed through that device or outlet.
Here is a brief explanation of these methods where two sets of type-nm cable wire are in each outlet box:
Series is where the two wires of each color are attached to the outlet terminal screws, blacks on the brass colored screws, white on the silver colored screws, OR the wires are stripped and pressed into the rear push-a-matic connections for some brands of outlets. This method can cause problems, especially when space heaters or large load devices are plugged into the circuit, the load is placed through each outlet wired with this method.
The Parallel method is where the two wires of each color are pigtailed or spliced using wire connectors to a third wired which is then connected to the outlet. With this method the load travel trough the splices, not the outlets.
As long as the splice is done properly by twisting the right length of wire and firmly screwing on the wire connector there should never be a problem. Now I know that there are situations with older homes where there are the smaller metal outlet boxes that do not have enough room for the pigtail splices, so in this case you will need to use the screw terminals. The ground wires for each method are typically twisted and spliced using a ground crimp. If a high consuming device is used such as a space heater then I would install a dedicated circuit and outlet for it.
From: Matt M
Thanks a lot for your quick answer to my question, I feel better about it now. I saw that you mentioned pig tailing the wires together by twisting them and then using a wire nut. I have always used the Ideal brand push in wire connectors in receptacles. Will these be okay left alone? If a wire should pop out in the future due to heating from a heavy load, is there a good chance that this could burn my house down, or will something simply stop working?
Thanks a lot.
From: Matt M Thank you for the video.
I don't see too many of those hazards in my own house, and I try to do things as safely as possible. As I mentioned I use those push in wire connectors, which I really hope are safe. I just fear that a wire will pop out of the connector, or will slide out from under a terminal screw on a receptacle or something like that.
There are a few receptacles in my home with 2 #14 gauge wires under one screw. When I replaced these receptacles, I really tried to make the screw nice and tight so it will be safe.
One final question I had was about reinstalling a switch or receptacle after replacing it. They say to fold the wires so that everything fits into the box neatly. But if the wires are pretty short, you can't really fold them very nicely. Since there are many outlets like that around my home, I would wrap them with electric tape after wiring them and then just push them back into the box, but not necessarily folding the wires.
Will this be safe left alone, or will the pressure cause the wires to come out from under the screws?
Thanks a lot for your help.
From Dave: Matt
Usually with a case where there is a loose connection devices will begin to work intermittently, the connection will begin arcing and eventually the connection will burn apart. Most of the time, a fire will not start if the connection is confined to a protective junction box, and it will depend on what type of wire and insulation material is involved. You may find this video useful: https://ask-the-electrician.com/video-home-electrical-wiring-safety.html And the links that follow give a summary and checklist of checks people can make to eliminate fire hazards in their homes.
Arc Fault Circuit Interrupters are mentioned to be installed on questionable circuits, and although this is a good idea I feel that due to the wiring methods used in older homes the AFCI will have a lot of nuisance trips, if it even stays on at all. AFCI's work best on isolated circuits such as bedrooms where there is a dedicated circuit for the AFCI. AFCI's will trip with just about any type of arc, even from some types of light bulbs, and they will not work if the neutral wire is shared with another circuit.
A lot of house fires are due to people overloading a circuit, including extension cords because the extension cord may not be the same size of wire and type of insulation as the circuit it is plugged into. This causes the wire insulation to melt and catch on fire, as you will see in the video.
Dave From: Matt M
Hi Dave, That's good to hear about the push in connectors. And yes, all of our receptacles and switches have a ground wire attached. As for the receptacle with 2 wires under one screw, I installed a new receptacle putting one wire on the screw and one in the stab in connection in the back. I know these are not the most reliable connection, but I know they're used all over my house. As long as they don't pose a fire hazard then I'm okay with using them. I would much rather have to call an electrician years down the road to fix it than call the fire department to put out my house. In most cases, would there be warning signs that there is a loose connection before a fire starts? Will something stop working, or would something like a failed stab in connection pose an immediate threat? I just don't like the idea that wires might be popping out of the back. I heard that this method of wiring is still used in new construction. Is that true?
Thanks for the help, Dave. I really appreciate it. Matt.
Hi Matt, You mentioned two #14 wires under one screw - that is not a good idea. Can you pigtail those? If I had that situation I would turn off the circuit, remove the old box and replace it with a larger box.
The task is tricky but it can be done without damaging the wall if you are very careful. I have pictures of this process, they just are not up on the website yet.
As for the push-in connections - the devices that have this capability are tested by the Underwriters Laboratories, and they are safe to use except when high load devices are placed on the circuit such as space heaters where they are going on and off allot. This can create a problem with push-in connections that are not pigtailed. I personally have used the push-in method, sometimes using the series method when wiring spec homes, and I have never had a call-back. I just make sure the insulation is stripped back as shown on the rear of the device and I'll even give the wires a tug to make sure they are locked in tightly.
When using this practice the wires will never pop out of the connector. Under ideal conditions where the junction boxes are larger and the wire sizes are longer then the wires can be folded back neatly into the box. In your case, because of the situation you have it sounds like you are doing the best you can, and wrapping the outlet with electrical tape is a great measure of protection as well.
It sounds like you have done a good job. I'm wondering if you have ground wires in all the outlet boxes?
One thing I see allot is people replacing 2-wire, ungrounded outlets with grounded outlets without having a ground connected. This is incorrect and a violation by code. The only way this is permitted is if the outlet being installed is a GFCI and the label is placed on the cover stating that the outlet is ungrounded. The GFCI still works, only by sensing current to ground through a device that is plugged into it, if such a condition is experienced.