5 Mistakes DIYers make using metal electrical boxes 

I learned how to properly use a metal box, I have never used a plastic box, in my high school electricity class. We did house wiring in grade 11, back in the late 60s. Back then, we used Marr connectors, instead of Wago, to join wires. One mistake I saw, in our own home, was in the receptacle near the kitchen sink. When the house was built, in the mid 50s, grounded outlets were only required near the kitchen sink and laundry tub. The "electrician", who wired that outlet, instead of extending the ground wire from the box to the outlet, used a nail under the outlet ground screw and touching the metal box!!!. By the time I saw that, many years later, the tip of the nail had rusted away, leaving the outlet ground terminal ungrounded!

Thank you very much for the very clear explanations.

Very well-prepared and presented video. Liked and subscribed!

Thank you Sir for all information you give 🙏

Great video. Thanks!

NEC 2020 says that the ground connection in the box should not be used for any other purpose. So you cant screw the ground conductor to the box AND use it for the device. A pigtail/second wire must be used.

Thanks. This is a great video.

Excellent, thank you.

Great info!

Nice video many folks would find useful since metal boxes in new residential construction are not nearly as commonplace as they were many years ago. Nonetheless there are certain applications around the house where plastic boxes are unacceptable, and we need to understand the differences in order to make safe electrical installations. As a side note, although not required, I like to wrap the switch or receptacle with a few layers of electrical tape before installing it in a metal box, especially in multi-gang switch boxes containing dimmers with screws instead of wire leads. You'll thank yourself for taking this extra step after a few times blowing up a $30 dimmer.

Thanks for the video. Very helpful. In the last situation with a short ground and adding a dimmer switch, can I use a straight through wago connector and screw only the long ground from the dimmer switch under the box screw?

I have seen conduit used as the ground and self grounding receptacle used will it pass inspection

We use a flat cable in the UK very similar with a ground/earth cable with no sheathing we call it Twin and Earth but we don't leave the bare copper cable exposed we add a sheath.

I was wondering why the switches in my 1978 house didn't have ground wires connected to them, rather only to the metal box. I now know from a little tid bit where you mentioned it. Thanks.

Most older steel boxes didn't have those grounding screws and required a green grounding clip to be installed. It might be nice if you addressed that problem with older steel boxes.

Also should have noted that if back-wiring the device, turn all the side screws in tightly to avoid possible contact with the metal box.

Here's another grounding mistake that was actually a fairly common practice 65 years ago or so. In the early to mid 1950s when NM cable with a ground wire begin to hit the market while 2 prong receptacles were still the norm, the electricians often wrapped the ground wire around the jacket of the cable before inserting it into the box and tightening the clamp. Assuming the whole circuit was wired with this new fangled grounded NM and all metal boxes you'd end up with what are known as "grounded two prong outlets "

The last house I moved out of was built in the 50s. Most plugs weren't grounded properly and 95% of them had live and neutral swapped because whoever renovated the house obviously wasn't an electrician. So, they put every receptacle in wrong. Being a guitar player, it wreaked havoc on my tube amp. The noise was terrible. Thank God I moved into a newer house that was built in the late 80s. When I plugged my amp and guitar up and turned them on, it was so quiet I thought maybe the power didn't turn on lol.

those are some great tips I see too many times that the wires are cut way to short !

When using Wago/wire nuts, I prefer that the Source romex ground wire be the one under the screw. The box stays grounded in case of other fails

Very informative, great job!

Hi- Thanks for the video. I have one question. In the video you connected the ground wire and a separate pigtail ground to the ground screw; then connected both to a Wago connector. My question is why did you need the pigtail ground if the incoming ground wire is already connected to the ground screw? Also could you have just pigtailed from the ground screw to the Wago, and then connected all other incoming ground wires to the Wago? Thanks!

I would add one edit to your list for DIY'ers using Metal boxes when Romex and other non class wires. Even when secured, the sharp edges of most boxes can cut into wire making the box live. Add bushings to protect your unclad wires be they Romex, Solid, Stranded Etc. Most DIY'ers think the bushings are for water proofing. I see it everyday.

The older bx wires had no ground wire but an aluminum grounding strip that is difficult to secure to the box.

I started off on painting/ drywall mud project in my house but decided I wanted to replace all of the new work plastic boxes that were installed in this house in 1990 with new work metal boxes. Reason being, the plastic boxes that were installed were of horrible quality and on just about every electrical receptacle that had frequent use, the plastic screw hole on the plastic boxes has cracked/stripped and so the only thing holding any back tension on the receptacles is the wiring itself. To make matters worse, the electricians used the old back stab wiring ports on every receptacle that I've taken out so far. So, with the stripped screws and back stab connections I had something that could easily turn into a house fire so I decided on using metal boxes b/c they're not going to strip or crack like the plastic ones and will have strong screw connection for a lifetime. I have good bit of drywall tools and experience and so I'm cutting the bottom 2 ft of drywall out in the guest bedroom where I started in b/c I'm also running brand new NM-b cable as well and with the drywall out of the way it makes installation of the boxes and fishing the new NM-B cable sooooo much easier. Thats also why I'm installing new work metal boxes instead of old work metal boxes. I don't like the old work boxes b/c so many of them come loose over time because they're secured to the drywall and not a stud. They're also prone to cause the drywall mud around them to crack. For the new receptacles, I'm going with some high-grade receptacles to replace the old ones (I think they were about $25 each). They are significantly heavier than the old cheap ones. I'm also adding an AFCI receptacle on the first box from the breaker and it will protect the other 4 downstream receptacles/fan/light. I bought the exact Wagos you have on the video (3 & 5 port). The first metal box will be an AFCI and it will have 1 load cable entering the box & 2 line cables exiting the box. Normally that would have been 5 ground wires tied together for that box but b/c the receptacles are self-grounding, that reduces it to 4. I learned how to do the box fill calculations recently and found out the box I originally had was not quite big enough so I had to up it to a 2-gang size box b/c they didn't make a 1 gang that would be large enough. Had to buy a special wall plate since its only 1 receptacle going in a 2-gang box. I do have a question for you though regarding the self-grounding receptacles / metal box- I had never heard of a self-grounding receptacle until I bought these but my understanding of them is that they're built differently and so when you screw a self-grounding receptacle to a metal box, it essentially bonds the receptacle to the metal box and so there is no need for 2 separate grounding pigtails ( 1 for the receptacle and 1 for the box) - instead you only need one pigtail. My question is when you tie that 1 grounding pigtail to the line/load ground wires, does code require you to tie the other end that 1 grounding pigtail to specifically the box or specifically to the grounding screw on the self-grounding receptacle? I wouldn't think it would matter b/c either way provides the grounding current a path back to the box, but does code or inspectors have a preference on which one you should tie the grounding pigtail to?

I installed a big, chunky GFCI outlet in a metal box. The outlet body was so large that it caused the hot screw to short out to the grounded box. I turned off the breaker after it popped and insulated the screws with electrical tape and also inserted a plastic tab between the outlet and the box as insulation. Never had that happen with light switches or standard outlets, but now I always use tape and an insulator tab whenever I install metal boxes.

In the UK, the earth (grounding) wire has to be sleeved, and most accessories have recessed line and neutral terminals to prevent shorting. Don't know why it's never been adopted in the US.

6:39. The existing ground wire is on the wrong side of the screw. Swap it to the right side and put the pigtail on the left.

I always like to run the ground wire(s) to the screw which will be nearest the neutral lead as well. A lesser chance of an errant ground lead touching a hot terminal. In my jurisdiction it is metal boxes all the way.

Talk about errors, my family and I were recently forced out of our home due to multiple code violations including no heat or hot water for months in upstate New York. I didn’t realize that for five years we were living with 100 amp service and only two 20 amp circuit breakers were working and hooked up to everything except the oven. Portable heaters were on low 24/7 and kicked the breaker 3 times a day causing multiple daily trips to the basement which was flooded with fecal water sewage. Absolute nightmare, boiling water to wash dishes, bathe etc. couldn’t cook food without tripping the breaker. No lights on ever, we used rechargeable led work lights and battery operated lights. 😞 Homeless in a hotel atm, family split up and looking for a new apartment.

The ground wire mentioned in the video is actually and technically called a bonding wire. Bonding and grounding is way different technically.

Interesting however plastic boxes and Romex are against code here. We always use metal boxes and conduit.

Do you have a video on wiring a junction box?

Why aren't all videos that clear!? Thanks!

I have noticed in the last few years (USA), metal boxes no longer come with 'included' grounding screws, but you MUST purchase them separately ! How cheep are those manufacturers getting!

I came across something different a few years ago. I have done a lot of LAN cabling in my time. A few years ago, while working in a new warehouse, I found I was running the LAN cables to a box with a divider, which separated the low voltage side from the AC side. The divider was made of the same steel as the rest of the box, so there was no chance of live AC touching the LAN cables. I saw that only on that one job and not since.

Many metal box plates DO NOT secure the romex well enough these days.

Interesting that on your last example of the clipped ground, you put it on the wrong side of the ground screw. It would also have been easier, and maybe better to take advantage of the second ground screw for the pigtail. Also you noted that the blastocyst box did not have a ridge next to the ground screw, but it does have a small bump which serves the same purpose.

At 6:26 mistake 3 is made

Our house has very old metal boxes. We had to reverse the polarity of several receptacles and discovered that the receptacle had a grounding wire going from its green screw to the plate tightening screw at the bottom of the box (that is used to secure the romex). Then the ground wire from the romex was secured to the plate tightening screw at the top of the box (also supposed to be used to secure the romex). We are not electricians and can’t afford one to remedy this. Does anyone know if we need to replace the metal boxes and redo all of this, or if the method the house came with is ok?

Why is there a Ground and Neutral wire. The neutral wire is grounded in the main box so it seems one would work. Is it a load issue or possibly an open/broken wire issue, or extra safety issue??

Question - can you use both grounding screws in a box? If you have three wires, can you put two on one screw as shown, and the third on the second screw? Thank you.

Screw in any extra terminal screws not used on recept installation, keeping them from possibly shorting to box. 😉

I think of a continuum of practice being bad practice, code, and best practice. Best practice can never violate code. For me, best practice is to reduce splices in the ground wire, so I run it long, wrap it around the ground screw, and then run it to the outlet or use it as a pigtail for multiple grounds. I don't like G-clips because they are more affected by corrosion, in spite of being allowed by code. To skip tightening down the cable clamps on the type of box shown requires one to neglect an obvious feature that is staring them in the face. While I've seen that happen, it's pretty rare. What is much more common is for the installer to fail to install cable clamps in other knockouts and in handy boxes, which do not have built in clamps. The other mistake is probably made out of ignorance, and that is overloading a box. Many DIYers have no understanding that there are code limits to the number of conductors in a box, based on its volume. BTW, there is a small benefit to using a plastic box on an exterior wall, as it creates less of a thermal bridge than does a metal box, as long as its depth is not greater.

I live in an older home, 1950s, how can I tell if the metal box is grounded? And if there is no ground wire, then what?

The ground wire to the box (metal) is a redundant exercise, as most if not all switches and outlets have grounded frames. It is still a good practice yo ensure secure grounding.

Why the specific need for a "#2 square screwdriver"?

Where to begin... Metal boxs where the outlet is wired backwards is a classic, suicide grounds - the ground of and outlet jumped to the neutral or the ground off them metal box connected to the neutral. Light switches wired to switch neutral rather than hot. 3 way switches using the bare ground as not a ground. This one is common one around here but metal 2 gang surface boxs on the end of an extension cord that is 14 AWG, with dual duplex 20 amp sockets on a metal wall plate, romex clamp holding the cord rather than a gland. and on the other end of the cord, you guessd it, ground pin cut off.. I admit I do have a collection of self built special purpose extension cords myself but they are all done properly. Gotta love the over stuffed in wall metal box where everything it too short, daisy chained and no matter how many breakers you turn off, something it still live, oh cant leave out the fluff of years and mice feces or bug carcasses... Stud boxs in the wall no where near a stud, just hanging on by faith, wall plates fastened with self tapping screws. Metal boxs fastened to a stub with pipe strapping and metal ducting tape, I see this mostly around HVAC equipment. I do admire the ability to improvise but yeah.. Ok I have used the metal tape to cover an accidental knockout until I got a proper plug for it. The use of wire nuts that are too small or not at all and it's just a layer of tape or better yet those automotive crimp on butt connectors.

I have seen boxes with 4 or more wires going into it and the people that installed it had two hot wires hooked the wrong way on one screw witch had caused a problem for other Receptacles down-the-line. Never understood why they couldn't just pig tail the wires instead of fighting with putting too many wires on one screw

Loads of steel boxes have no ground screw. If the ground wire is attached to the switch or receptacle ground screw, the box will be grounded when the switch/receptacle is screwed to the box.

Supply houses sell bundles of green insulated ground stingers. Most come with a loop and a ground screw on one end. You screw it into the threaded hole in the box and pigtail all the grounds together. Always use a wirenut. Why? Because by code most multiple wire connections are required to be mechanically sound without the device holding them together. For example if you take three neutral wires and remove the wire nut the wires must remain in mechanical contact with each other by being twisted together. You can't do that with a wago. So wago's would be illegal on a multi wire branch circuit. Personally after forty years as a commercial electrician I truly don't trust any type of spring pressure connector to hold a good connection for decades. I've often run across work done fifty or more years ago that was just as good as the day it was done. Years ago a friend asked me to come over and check her refrigerator. It was out in the garage and the cord cap and outlet had melted. I pulled it apart to find it had been wired with aluminum. Lots of wire so I cut off all the crystalized wire and put a cu/al receptacle in the box and replaced the cord cap on the fridge. Turned it on and it worked. I asked the neighbor why his custom built home was wired with aluminum. He said the builder wanted him to decide for copper or aluminum so he talked to his father in law who was an electrical engineer and his fil told him the aluminum was just as good as the copper and cheaper so go with it. At the time aluminum was legal and widely used. Unfortunately time would prove it to be a bad decision. I expect spring pressure connectors will eventually be as unpopular as quick wire receptacles.

Last picture of metal box, white wire is on wrong side of grounding screw.

I always splice 1 pigtail to go to the box, and 1 for each device to the grounding conductor using a wire nut. It's much simpler.

Am I seeing this correct? At @6:25 the white wire, which would be neutral where I live and not what you would connect to a ground, is entering under the screw from the wrong direction.

If light switches do not need a ground, why is there a grounding screw on the switch???

It is also good practice to wrap a few layers of electrical tape around the terminals on the outlet to avoid any contact with the metal box.

For components like a NEMA 5 outlet that needs grounding, isn't the component frame connected to the component ground? In this case, isn't a metal box connected to a grounded component grounded through the component frame, component ground screw, and ground wire? Why does the box need to be separately grounded?

6:20 is it legit to screw the green ground wire from the switch directly to the screw?

It’s safe to install electric tape around the screws outlet ?

If you convert an old two prong outlet into a GFCI one and the metal box is not grounded, it will not be safe. If the live wire touches the box it energize any equipment case and the GFCI will NOT protect. One would need a GFCI upstream to protect.

Mistake #5 shows an example of a ground wire cut at the screw. This wire is on the wrong side of the screw (mistake #3). The pigtail was installed correctly, but the ground wire should have been corrected first.

Should we use a conduit?

This must be the fiftieth, possibly the hundredth, vlog about how to install a device box and they're still not getting them correct???

The think that it worries me is plastic Romex boxes in a comercial or industrial building. Where are the real inspectors especially in California??? I have seen so many illegal installations in comercial buildings that is sad!!!!

The sharp edges around the hole in a metal box is much safer when you insert a rubber grommet first .

I had water damage that was going to require major renovations and the contractor doing the estimate said it would require code updates. He stated the metal electrical boxes would need to be replaced because they are only allowed in commercial applications. Does anyone know if metal boxes are forbidden in residential applications in Michigan?

Typically the bonding screw electricians will loop around the bonding screw and the others will be pigtailed (the bond then goes to the device) depending on the situations . Waggo connectors are shit.

Try doing that with 240V AC similar to what we use in the U.K. Trust me, your mistakes will be a lot more painful.

hate those wago connectors. i've replaced plenty of burnt out ones, they simply don't hold up to any current. BTW 10 year electrician speaking

Do not use wahoo connections for electrical outlets they cannot handle the a load I've seen too many Wires turning purple and insulation melting walk wahoo connectors are great for doing electrical circuits and lighting low amperage

From an electrician: most of these issues mentioned are also common to plastic boxes. Specific to steel boxes: don’t enter more than one cable together under one half of the clamp, make sure the clamp is approved for the type of cable you are entering, make sure you are using boxes for their intended purpose, box fill limitations must be adhered to as standard size steel boxes are much smaller than standard size plastic boxes, ensure neutral wire does not contact side of box or afci circuits will trip.

Mistake #1 is using metal boxes. There are only a ^maybe^ couple reasons to use metal boxes with NM cable.

Sad to see these mistakes

The 5th mistake mentioned is not leaving enough ground wire to connect to the device being inserted into the box after connecting the ground wire to the metal box. There are some ways around that. Many new devices are self-grounding and will pick up the ground from the metal box itself, no ground wire needed. The device will have to say in its specs that it is self-grounding, but a way to tell is that usually they'll have a brass clip where one of the mounting screws goes through. Be sure to read the instructions, if there's a washer on the back to hold the screw in place before insertion, that washer may also need to be removed. Another option in the example shown would be to use the other grounding screw in the box to create a pigtail or, if your device comes with wires attached already (and if long enough), connect that ground wire to the other grounding screw.

Thanks for the video. Question when you removed the knockout hole cover do you use rubber grommet to protect the wire from the sharp edge

Mistakes that I have seen in metal electrical boxes. The previous person did not wrap the outlet with electrical tape. Thus if removing the outlet and if the power is still on, the power screw can contact the box and create an arc. Oh that is not fun.

I don't think connecting the ground wire to the metal box does anything useful when using romex (as opposed to metal conduit, flex or rigid). The ground happens back at the main panel. The ground wire is connected to the ground bar which is connected to a ground rod. If metal conduit is used, the metal box is grounded back to the panel. Please explain how grounding the box does anything useful when using romex.

you need to mention the amount of wires permitted in an box each has a finite amount of wires allowed!

Just don't buy conductive junction boxes. Most logical solution.

Currently NEC does not stipulate for boxes. There are also nylon. When I rise to power, that will change. Only metal boxes will be code. Plastic and nylon will be banned and non code compliant. I hope the NEC pulls their head out of their @$$ soon. Whenever they do, it can't ever be soon enough. A simple light switch DOES require a ground wire. Why would you say it does not ? There is also a grounding screw on the light switch. The switch carried line power and if shorted can shock you if you touch screws or have metal plates.

i see in metal boxes the switches and outlets screws are not tape

I thought metal boxes were only required for industrial/commercial applications, for the 2nd ground that the conduit affords? Without the conduit running back to the breaker box, metal receptacle boxes are pointless IMO. I've seen some people loosely wrap the entire receptacle with electrical tape, around the terminals. When I see that I think "just use a damn plastic box" lol

Nice video... I remember when I was about 21 or 22 years old... I made sum electrical boxes out of wood 🪵 and more than ten years later those boxes I made are still in good condition... 🫡😳

Not breaking off the ears of receptacles or switches when mounting a metal box that is not flush with a wall surface while using a standard wall plate.

I never understood the metal box concept in homes. I do realize plastic molding technology was not common say in the 1960's and 1970's but for codes requiring metal boxes in residential settings today is absurd. I have worked on many older projects. I do my best to suggest a retro fit of a plastic box in place of metal. However if the person I am working for will not allow it, I will leave them. One thing I do is wrap the electrical device, be it a receptacle or switch, in a high quality rubber electrical tape. This is just another layer of protection against shorting the connections to the box. Here is some advice. If you work on or own an older home that you are remodeling please do these things. If the main panel is a fuse box, replace it with a breaker panel. If the conductors are cloth covered, rewire it. If the conductors are aluminum, definitely rewire it. Rodents love the taste of the vinyl coating on conductors. Check frequently for rodent damage on exposed romex. If they have chewed the sheath tape it and get some pest control. If they have chewed the coating on the conductor, replace it and get some pest control.

At 6:26, why didn't you put the existing ground wire on the right side of the screw so that tightening the screw pulls the wire in instead of pushing it out? This is literally one of the common mistakes that you complain about!

Metal or plastic if it’s a device box or any other box the continuity of the bond must continue down stream and be also bonded to any non current carry metal parts. If not sure please hire a professional certified electrician instead of watching RU-vid videos

use plastic boxes when you can. i ama electrician

Commercial electrician here. Don’t put more than 1 wire under a ground screw, simply use a ground pigtail and attach all your grounds to said pigtail. Also there are more metal boxes out there than the one he showed; always use an appropriate box connector to ensure the wire is kept both secure and free from damage. Also be aware metal device boxes aren’t always allowed in residential wiring based on jurisdiction for new work.

Anyone who says Wagos are crap is someone who clings to old ways with a closed mind. Don't listen to another thing that person says about anything, because that is absolutely not true.

If anything that was covered is new to you, do not try it yourself without having a pro look it over.

Wago's are CRAP!

I’m not too sure why someone who is not an electrician make these videos…

Step 1. use a plastic box!

6:21 One of the ground wires is in backwards. You're welcome.

I thought that I might pick up a point or two. Not happening. I will not use romex. In my opinion romex should be illegal. MC is the cable of my choice. Don’t lecture me on the correct connectors. I’m an NEC kind of guy.

nothing new here except the connectors, all just basic knowledge,

It makes me cringe when I see a guy using wahoo connectors for electrical outlets please do not use these please do not start a fire.

Mistake number 6, using Wago connectors. Using them is no different than back wiring a receptacle, everyone know not to do that.

Good video I guess, but let’s be perfectly honest, residential guys are dangerous as it is, let alone all the home owners trying to play electrician. Commercial/industrial journeyman can easily do residential work, but it doesn’t work the other way. Same thing with utility side. Lineman can’t do what a commercial/industrial journeyman can, but we can easily work utility lines. There’s a reason we cost what we cost, we’re part mechanic, part engineer and part fabricator and installer. We are the king of all trades.