Types of Wire in a Home (Residential)

This article covers different wire types in a home for power.

For more information on where wires are allowed to be installed, look at Table 19 in the Canadian Electrical Code Book.

– JackElectrician (YouTube Comment!)

Table 19 explains “Trade Designation” (type of wire), “Conditions of use” (where a wire is allowed to beused), “CSA type designation” (shortname for the wire), and temperature the conductor insulation is rated for!

Please continue to give your feedback and corrections. I should have definitely included Table 19 in the video for your own research.. thank-you JackElectrician! I often try to avoid code as things change too often to maintain, but Table 19 is a very useful to understand wire types as an electrician in Canada.

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What We Cover in this Article:

• Different Types of Wires in a Home (for Power)
• How to Find Where Wires Are Allowed to Be Used (Table 19)

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Different Types of Wires in a Home (for Power)

The video above breaks down that in Canada, we mainly use NMD90 as wire type. This is rated FT1, which means you have to be careful where it’s being pulled, such as in air duct plenums! (This relates to low-voltage wire, too!)

Regarding FT1, you can learn more in Appenix B: 2-130. (Remember, in code tests, teachers ALWAYS make you look in Appendix B for answers!).

FT stands for “flame test” with different ratings, like FT1, FT2, FT4, FT5, and FT6. Each test undergoes a certain procedure which exposes the wire to flame and it must pass under certain conditions.

If you only have FT1 wire, many times it’s easiest to just avoid particular areas, rather than get the special cable required. Reading your jobsite specifications in the back of your electrical prints can always provide more details, too!

When reading a wire like 14/2, understand we count insulated conductors (not the bare bond wire!).

Example: If 14/3, we have 3 insulated conductors, plus a bare bond wire.

Tricky Example: In fire alarm cable, the bond wire is insulated green, which means it’s counted! If you order 14/2 fire alarm wire, there’s only two conductors (red & black.. no bond!). If you need the bond in fire alarm cable, you’d order 14/3 for its 2 conductors + insulated bond!!!

In the Canadian Electrical Code Book, understand some tables “trump” general tables. In other words, if a table with more weight says something different, those rules apply over the general rules.

For example, Section 14 of the Canadian Electrical Code is Protection and Control. Rule 14-104 (2) is a general rule about the maxium overcurrent protection for certain size of wires.. at the time writing, that is:

• 15A for #14 AWG copper conductors
• 20A for #12 AWG copper conductors
• 30A for #10 AWG copper conductors

This rule tell us we cannot have a bigger circuit breaker for these wire sizes for typical installations (general rules).

But.. (summarized).. Rule 14-104 (1)(c):

The overcurrcent device shall not exceed allowable ampacity of condutors they protect, except…. as provided for by other Rules of this Code.

If working with motors (Section 28), that section takes precedence regarding ampacity of wire size, breaker size, etc.. as Section 28 can upsize breakers and fuses 200-300% in some cases because of “in-rush current”.. otherwise the breaker will always trip when a motor first starts!

In Table 2, notice #14 is rated for 20A in 75 degree column? But we’re told #14 is rated for 15A? This is because 15A is for GENERAL use.. where we don’t know the application. (Why do we use 75 degree column? Because most equipment [breakers] are 75 degree rated, even though wire insulation is 90 degree rated!)

Wiring a residential home typically falls under “general rules” for basic plugs and switches, because as electricians, we often don’t know what the user will be plugging in, so we must wire it according to code, to protect the wire.

If the customer explains a certain plug will be for a high-demand load, let’s say 30A, we then need to make provisions for that purpose to ensure the wire has proper overcurrent protection (circuit breaker, fuse, etc), and.. that the House Calculation still meets the main home’s feeder size!

I will now repeat what was shown in the video, showing pictures of:

• #14/2
• #12/2
• #12/3
• #10/2
• #10/3
• #8/3

Please refer to 12/3 to compare with 14/3 (I didn’t have any on hand, sorry!)

14/2 Wire Common Uses in a Home

#14/2 NMD90 is our most common wire as electricians in a home.

It’s used for basic plugs and switches (general use), rated for 15 Amps, which means electrical devices like plugs and switches need to be rated for 15 Amps, AND the circuit breaker must protect the 15 Amp wire, too!

As electricians, #14 is often used for Fridges, Dishwashers, Washing Machines, Microwaves, basic plugs and lights, and sometimes for the bathroom GFCI (it’s best to run a #12, though!)

Other uses of 14/2 wire are for Switch Legs. Back in the day, if power was at a light, electricians would run power down the white wire to the switch box, then switch the black wire back up. (This is no longer common, because a neutral must always be in a box due to newer smart devices!).

Sometimes in a commercial setting, we use 14/2 NMD90 as two hot wires (208V in 3-Phase), instead of one hot and a neutral (120V).

Remember, underneath a conductor’s insulation is just copper.. The color is used only to help electricians identify which wire is which, and to follow code rules.

The Black wire could be A Phase, and the White wire B Phase! Depending on the electrical panel, this could provide 240V or 208V to a single phase motor!

Never use the bond wire as a conductor!!! – I’ve heard of electricians doing this as a last resort.. super dangerous.. only use a bond wire to ensure equipment is not energized (safety)!

14/3 Wire Common Uses in a Home

The most common use of 14/3 wire in a home is for 3-way and 4-way switches.

14/3 has 3 insulated conductors, and a bare bond wire. We use these 3 insulated conductors in a 14/3 wire as travellers which connect between switches to turn on and off a light from multiple locations.

The Feed and Switch method was very common when wiring a 3-Way Switch, but this gives a dead-end (no neutral), which is no longer allowed, as every switch box needs a neutral for smart devices!

Did you know there’s 8 ways to wire a 3-way switch? (The secret is keeping it as simple as possible for maintence purposes. Remember, never run power to a light box.)

Another common use of 14/3 in a home is for ceiling fans.

The red wire turns the ceiling fan light on and off, while the black wire is for the actual ceiling fan. (The black can either be wired for a pull string, its own switch, or spliced together with the red to turn the light and fan on together).

Many years ago, 14/3 was also used for kitchen counter plugs to provide two circuits, but share a neutral (Edison 3-Wire Circuit). This is bad practice, as if you lose the neutral, the circuit turns into a 240V series circuit.

Today, kitchen counter plugs now get its own #12 home run, with a max of two plugs on one circuit, which we cover below.

Another use of 14/3 wire is breaking the metal tab of a plug to create a Split Receptacle Outlet (with the same circuit). The top plug can then be switched, while the bottom plug has constant power!

One last use I can think of for #14/3 is for photo-voltaic switches (photo-eye). In a commercial condo / apartment building there’s often a photo-eye on top of the building to turn off and on the outdoor lights depending on the sunlight. (Sometimes they combine both a timer and a photo-voltaic switch!).

12/2 Wire Common Uses in a Home

#12/2 NMD90 is most often used for kitchen counter plugs in a residential setting.

In a commercial setting, every plug and light is typically #12/2!

Also, if the wire length is too long with #14/2, we often upsize to #12/2 for voltage drop.. generally rule of thumb is every 100′ feet you upsize to the next wire size.

Rules keep changing for how to wire kitchen counter plugs, and what size of wire for counter plugs, over my electrical years.

Previously, electricians used 14/3 which provided each plug its own circuit, but shared a neutral. In theory this seems good (and affordable as you reduce one wire), but in practice, it’s not, if you lose the neutral (like a drywall screw into a wire!)

Why? If you lose the neutral, you create a 240V series circuit with electrical devices which were intended for 120V! If each device resistance is not the same, one load gets way more voltage (boom), and the other load is undervolted!

This is called an Edison 3-Wire Circuit (Multi-Wire Branch Circuit). Companies try saving a dollar with this, but I’ve heard court stories (sued) from this wiring approach.. a drywaller screwing into a neutral, and the fridge gets destroyed.

So what do you do? Don’t share the neutral on kitchen counter plugs, and you’ll never run into this issue. (Even in commercial wire sets, it was becoming common that everything gets its own neutral.. This increases cost and pipe fill, but reduces these types of issues later on).

Anyways, today kitchen counter plugs are #12. We pull a dedicated #12/2 home run to a kitchen counter plug, and no more than 2 plugs are spliced onto a kitchen counter plug circuit.

Another use of #12/2 as electricians is for PTACs (Packaged terminal air conditioner), which are self-contained heating and air conditioning systems often mounted to a wall. These units often receive 208V, so we just provide both insulated conductors (black and white) to power this unit (no neutral required).

12/3 Wire Common Uses in a Home

In a residential setting, 12/3 NMD90 was not commonly used, as we’d use 14/3 for most situations, like 3-way and 4-way switches. This is to keep costs down, as electrical code provides the bare minimum we’re allowed to install.

However, in a commercial setting, #12 is almost always required as a minimum wire size, so #12/3 was used in place of #14/3. For these reasons, #12/3 NMD90 is not commonly used in a home.

But, in most commercial buildings, we often deal with metal studs, or installing EMT pipe (single condutors), so we do often use #12/3 AC90 (armored cable.. BX).

The odd time I would be on a commercial jobsite with woodframing. In these situations we may use 12/3 for 3-Way and 4-Way switches to comply with the electrical specs of the jobsite (as commercial wiring is almost always minimum #12 for plugs and lighting).

10/2 Wire Common Uses in a Home

#10/2 NMD90 is often used for Air Conditioners in a home. (Or dedicated motor loads). In the case of a motor, like an air conditioner, we are not using the white wire as a neutral.

We’d use Black as one phase, and White as another phase to create 240V for heavier loads in a home. (If you’re on a three-phase panel, this would be 208V single-phase).

In condos and apartment buildings, emergency lighting is often #10.

So #10/2 is often pulled to emergency light heads because they are run off DC (batteries), and the upsize of wire is crucial for low voltage drop so EM Lights are as bright as possible.

10/3 Wire Common Uses in a Home

#10/3 is most often used for a dryer (for drying clothes) in a home.

A 10/3 NMD90 wire has three insulated conductors, a Red, Black and White.

The red and black conductors provide 240V for the heating elementor (and I assume motor load) of the dryer.. but he dryer also requires 120V for the lightbulb and its electronics, so we use the white wire and one phase (Red or Black), to create 120V for this purpose. (This is done within the dryer itself by the manufactuerer.. we just wire up the wires to the unit’s diagram).

Other than a clothes dryer, 10/3 NMD90 is not commonly used in a home.

Remember, cost increases tremendously with wire size, so when talking about 10/3 and 8/3, we want to provide the bare minimum wire size required to such equipment to reduce cost, but still provide adequate amperage for now, and in the future.

Never leave out #10/3 or #8/3 on a jobsite over night!! Sometimes we forget #14 or #12 out.. this is still bad, but #10 and upward is a big mistake!

8/3 Wire Common Uses in a Home

#8/3 is most often used for a range (your stoven / oven) in a home.

Voltage may differ at the electrical panel, depending if it’s a single dwelling (single family home), or condo / apartment, but electrical theory regarding how voltage works is the same.

Typically, single family homes are 240V, and apartment / condos are 208V (due to the building’s electrical panel being three-phase).

Three-phase means there’s three hot wires [A Phase, B Phase, C Phase]. Careful, because you can have 208V Single Phase [A + B Phase] or 208V Three Phase [A + B + C Phase]. This is why it’s very important to read the nameplate of equipment.

An #8/3 cable has three insulated wires (red, black, white), and a bare wire (which is your bond wire). Two insulated wires are your hots (red and black), the white is used as a neutral (for 120V), and the bare wire (bond) is always used as a form of protection so equipment chassis cannot be energized!

We use two hot wires (red & black) to create 240V (or 208V Three-Phase) to reduce the size of the cable for the requied wattage, but 120V is required for the electronics on the electric range like the clock, timer, or other digital settings!

So one hot and a neutral gives 120V, but for the stove-top elements and oven element, two phases are used to provide 240V (208V in three-phase).

If you want 1500W on 120V, your single hot conductor needs to handle 12.5A!

With this 120V example, if a stove has 4 elements, your cable needs to handle 50A (12.5 x 4).. not including the oven where you bake delicious cookies 🍪!

So, 240V allows us to reduce the wire size (which reduces cost).

Let’s say an oven is rated for 12,000W:

12000W / 240V = 50A..

But if you’ve taken your electrical schooling regarding house calculations, you know we do not calculate a range this way, where many online resources will say this is how it’s done. A range is not calculated like other electrical loads, like a hot water tank, for example.

Depending if you’re in Canada or USA, the code gives us a flat number to use, then a percentage to include after a certain wattage demand. (This is why range breakers are often 40A). This is because a range’s electric elements turn off and on (non-continuous), and it’s rare the range will use its full wattage rating at once!

How to Find Where Wires Are Allowed to Be Used (Table 19)

Refer to Table 19 (for all wires, except flexible cords) and Table 13 (for flexible cords, like light and lamp wire, or christmas-tree cord wire). These tables in the Canadian Electrical Code Book will guide you for when to use wires in different situations.

In a residential setting, we mostly use NMD90 for branch circuitry, where we bring a home run from the electrical panel to an electrical device (like a plug), then splice from box to box.

For what wire type for a home’s main feeder, in Canada, we often used ACWU90. This is typically the only situation we can still use aluminum wire, which most home insurance companies will allow.

Many times we refer to ACWU90 as “Teck Cable [TECK90]”, but TECK90 is actually copper, and has plastic inner sheath around the conductors. (It seems you can also order TECK90 as aluminum.. but this is not common).

Aluminum suffers from oxidization (exposed to air), galvanic corrision (when two dissimilar metal touch), as well as termal expansion (heat and cooling). Because of this, it was always recommended to use Antioxidant Paste, also known as deox, penetrox, or noalox on the conductors before terminating under a lug.

(After some quick research online, there seems to be debate on the topic of is Deox Required on Aluminum wire, and if it’s really needed.. interesting read..)

I hope you enjoyed this article about different types of wires in a residential settings (for power).