Episode 14 - Knob & Tube Wiring

Trevor Tremblay: It is very easy to determine if you have knob and tube. If your basement is unfinished, essentially just go downstairs, look up. Hey, there it is. You'll see the white tubes, you'll see the knobs. You'll see the insulated conductors, hopefully with insulation on it. Unfortunately, a lot of people convert the knob and tube where it's exposed to where it goes up the wall. So you might actually have to do further investigation to find out if you have knob and tube. If it's properly installed and maintained, it is very safe. Unfortunately, over time, time always wins. An older home, you're going to have multiple generations of wiring as their needs increase. You'll see aluminum extending from knob and tube, which is not allowed. You'll see new wiring methods intermixed so it could become a problem over time.

Karen Ras: Grounded in Ontario is a podcast for you, the province's licensed electrical contractors, master and certified electricians, and offers safety tips, tech and best practices. Now let's get grounded. I am Karen Ras and I work for the Electrical Safety Authority. I've got Trevor Tremblay back in the studio with me today and we're going old school and talking all about knob and tube. How are you doing today, Trevor?

Trevor Tremblay: Very well, Karen. Thanks for asking. I'm very excited to chat about knob and tube.

Karen Ras: Now, knob and tube seems like it's a blast from the past, but could be useful for those newer contractors who've never seen this type of installation before. Trevor, as a non-technical person, can you explain knob and tube wiring and how common it is in homes across Ontario?

Trevor Tremblay: Knob and tube is still very common in older homes, say 1950s era and earlier. It's definitely been around a lot longer than I've been. It's essentially just two conductors. Insulated conductors run throughout the house and it gets its name, knob and tube from the parts that are actually used in the installation. So every time you go through a structural member, you need a ceramic tube, which the tube comes from, and you have standoffs, ceramic standoffs, which essentially you tie your conductors down to when you're running along structural members. And these insulated conductors essentially just have a rubber rice cloth-like insulation on it, which can over time become brittle. Anytime you want to tap off that, it was always soldered and then just taped up to make it safe. One drawback is it didn't have a bond wire, so a lot of the time, you had the two-prong receptacles in your older homes. It's very easy to determine if you have knob and tube, if your basement is unfinished because you can essentially just go downstairs, look up, Hey, there it is. You'll see the white tubes, you'll see the knobs, you'll see the insulated conductors hopefully with insulation on it. Unfortunately, a lot of people convert the knob and tube where it's exposed to where it goes up the wall, so you might actually have to do further investigation to find out if you have knob and tube.

Karen Ras: Okay. Now considering all of this is knob and tube wiring safe?

Trevor Tremblay: Yes, knob and tube is safe. It's just like any other installation. If it's properly installed and maintained, it is very safe. Unfortunately over time, time always wins. An older home you're going to have multiple generations of wiring, so as their needs increase, you'll see aluminum extending from knob and tube, which is not allowed. You'll see new wiring methods intermixed, so it could become a problem over time and the code isn't retroactive, so we don't actually tell you to not install it. You can actually install knob and tube up until I think the last code cycle. You would've had to run a bond wire with it, but you were still allowed to install it. And I’ve actually seen in my history with ESA over 18 years, I've actually seen two installations with knob and tube. I'm not sure where they found all the parts. Unfortunately, they didn't run a bond wire either, so they couldn't really use it.

Karen Ras: Interesting. Now, as someone like me who relies heavily on electrical devices, are there any concerns with plugging into a home that is wired with knob and tube?

Trevor Tremblay: Since the system is probably up to a hundred years old? We already mentioned time plays a big factor. It always wins, deteriorated installation, and if you don't properly maintain it, it could pose a hazard. Unfortunately, back in the day, they had very few circuits in a home because they didn't have the electricity needs they have today. Today we have dedicated circuits for fridges, microwaves, countertop, receptacles, outdoor receptacles. Back then you had one circuit that did your countertops, your fridge, your outdoor receptacle. So every time you plugged in your block heater outside and you put your microwave on in your kitchen, it would blow. People would tend to replace the fuse originally with a 15 amp, and then when that blew again, then it went to a 20, and then when that blew again, it went to a 25. So the older homes, depending on how you load your circuits, it possibly could pose a hazard.

Karen Ras: Well, this certainly brings us back to a simpler time. Can you add to that, Trevor, are you aware of any cases where homeowners modified their knob and tube system to accommodate those heavier loads?

Trevor Tremblay: It happens all the time. The over fusing is one of the bigger things, but you also see people extending new wiring methods from knob and tube over time, people are going to modify their installation to address newer needs, newer loads, and they extended their knob and tube with the newer wiring that comes with a bond wire. So when you get to the other end and you install your receptacle, people put in a three-prong receptacle. Unfortunately, that bond wire goes nowhere and people have the assumption that it actually is bonded. When they are replacing the two-pronged receptacles with three-prong, they have to make sure they're using ground fault circuit interrupters. This can be done quite easily at the panel, so you remove the wire at the panel, put in your device box, use your GFCI receptacle, there's a line load feature and it protects the whole circuit. We recommend doing that to all the unbonded circuits when they're doing this work, and a notification is required.

Karen Ras: Now you've said a couple of times that time is not our friend, especially when it comes to knob and tube, and I think that can probably go for any infrastructure. What is the life expectancy of knob and tube wiring?

Trevor Tremblay: If properly maintained over time, it could last a lifetime. The only problem is that it doesn't meet today's demands on the electrical system. Those circuits are always going to be overloaded. The installation, typically where it's exposed, is usually where it gets damaged. If you look in people's basements, it's run across. The easiest way to store stuff is right in the floor joists right above the wiring. People don't know it's wiring, they just assume it's a nice place that supports all their spare baseboards and stuff like that, and that's where usually all the installation falls off. That's why a lot of people change it in the basement to where it goes up the walls, because going up the walls, it's not exposed to any damage and it's actually usually when you remove the wall coverings, it's actually pretty pristine. And that's at the receptacle outlets too and where lights are, if you do a lot of changes or modifications, those wires tend to get brittle and the installation falls off there just over time. And from heating and regular use.

Karen Ras:  And changing out, this wiring is not outrageously expensive from what I understand, correct?

Trevor Tremblay: Typically it's not. Most homes can be done. Hopefully the basement's unfinished. That would definitely help because a lot of it can be fished up. Multi-level homes might be a little more, you typically don't have to remove all the wall coverings. A lot of times you might just have to drill specific holes or cut openings just in certain areas to bring the wires from floor to floor. And one thing to watch out for is possibly there could be asbestos in some of these older homes. And that's one thing to look out for when cutting open these walls.

Karen Ras: I think it's important for LEDs who are listening to understand the risks and hazards that they may experience as well as some of their clients, the homeowners. Can you tell me a little bit more about home insurance?

Trevor Tremblay: So it's always a good idea to get your insurance company involved and let them know what type of wiring is in your home. They might possibly say no. It's always a good idea to consult your insurance company and discuss the requirements of homes with existing knob and tube and possibly aluminum. They may even ask what type of service and require you to either upgrade your service and possibly the wiring.

Karen Ras: Now, Trevor, what would your advice be to lacs who are working on knob and tube or would like to?

Trevor Tremblay: My advice would be from what I could see in the industry is that a lot of these older homes and people that own them have a hard time finding electrical contractors to do this work. I think it'd be a great business model and trying to advertise that you actually specialize in this type of thing and once you get good at it, it could be quite profitable. So I'd recommend capitalizing on this little niche market and it's not that niche. You could advertise in older neighborhoods and probably get tons of work.

Karen Ras: See, that's why I love the Grounded in Ontario podcast. Not only are we giving you safety tips, but we're also giving you business tips. Now back to the knob and tube wiring. What can LEC's do to maintain that knob and tube wiring?

Trevor Tremblay: The first thing they'll do is inspect the whole system. Anything that's visible, inspected, make sure that the installation is actually still there. A lot of times where it's exposed, it's been beaten up, so they probably have to replace it, open up the devices, make sure that the installation on the conductors inside of your device boxes are still there. Check to see what's on your circuit. New circuits might have to be run. Like I said earlier, you possibly could have your outdoor receptacle, your kitchen counters and your fridge all on one circuit, which tends over fusing of breakers or fuses, sorry, they'd have to double check. If you did replace the two prong receptacles, that actually is GFCI protected. If you're replaced with three prongs, I do recommend for the most part, if it's exposed, replace it. Like I said, inside the walls is usually pristine, so I wouldn't go out of my way to do too much other than that. But at the end of the day, it's an old system and updating is something you probably should do.

Karen Ras: So let's say I want to update my home's wiring from knob and tube. Let's walk through some of the most commonly asked questions. Do you need to gut the walls to replace knob and tube wiring?

Trevor Tremblay: Typically not. Some cases you might have to remove some wall coverings. A lot of times it's simply just cutting little holes here and there just so they can fish wires up and down. Multi-levels two or three story houses would be a lot more difficult, but at the end of the day, it's not going to be a total gut.

Karen Ras: Okay, and do you need to remove all the knob and tube wiring before rewiring is complete?

Trevor Tremblay: If you do run new wiring, the knob and tube that's actually visible would have to be just cut out. It's fairly simple to do. And anything that's not exposed and goes up through the wall, essentially just cut it at the wall or at the structural, remember where it's going and then just push it in so no one can use it after that.

Karen Ras: Okay. Now, do I need to add outlets around my house to bring it up to current code while having the knob and tube replaced?

Trevor Tremblay: If you're just bringing new wiring to your existing outlet, then no. We do recommend that you add existing outlets because typically they're never in the right spot. You don't want extension cords sitting there running behind covers. They're designed for temporary use, not for permanent, and if you actually remove all the wall coverings, then you would have to bring that area up to code and meet the minimum coverage for receptacles in that area.

Karen Ras: Thank you, Trevor. Certainly a big role for LECS to play when contending with knob and tube wiring in homes. Century homes are beautiful, but old technology comes with its challenges. Before I let you go, we did have a question from a listener, Jason in Hamilton asks, is it acceptable to terminate the grounded white conductor to the existing bonding lug supplied within the meter base specifically for a GenerLink installation?

Trevor Tremblay: Thanks for asking Jason. This is actually a fairly hot topic with us and some utilities at the moment. So when you are installing a GenerLink, it comes with a white number 10 tail depending on the size of your GenerLink, and that has to terminate somewhere in your meter base. Typically, meter bases don't have enough lugs or connection points to install this connection properly. So you'd have to actually use an insulation displacement connector if you're using USEI-90, which will actually cut the installation, make sure you take off one jacket because sometimes the teeth aren't big enough to bite through both jackets. If you're using copper, you can use a split bolt right to the neutral on the load side of the meter base. You can't put the white conductor right to the case. It has to be done in approved wiring methods and hopefully there is enough lugs in your meter base, but typically there isn't. So there's a couple ways to do it and putting it into the box is not the right way to do it.

Karen Ras: Alright, good information yet again, that's all the time we have for today. Thank you for joining us, Trevor.

Trevor Tremblay: Thanks. It's been totally tubular.

Karen Ras: Thank you again, Trevor. Always a pleasure. And thank you to listeners for sending in these questions. We want to hear from you, so please email us at podcast@esasafe.com. We're open to topic suggestions, questions and comments. Make sure you subscribe on any platform where you get your podcasts so that you'll get notified about our next episode. Until next time, be safe, work safe and stay grounded.