This is Part-2 of our 4-Part Article About Knob & Tube (K&N) Electrical Wiring. Al’s Plumbing — in Plano, TX provides Full-Service Plumbing; maintenance, repairs, and replacements for every plumbing component in your home. Al’s sells and installs gas and electric water heaters. Al’s is near your home in; Plano, TX; Allen, TX; Frisco, TX; and McKinney, Texas. We service all homes in southern Collin County, TX, and northeastern Dallas County, TX with no additional travel charges.
Call Al’s Today To Discuss Any Concerns Or Problems You Have With Your Home’s Plumbing.
We will arrange an appointment at your convenience.
This Is Part-2 Of Our 4-Part Article With In-Depth Details About
Knob & Tube (K&T) Electrical Wiring — In Homes Built (up to) 1955
Click Here To Go To Part-1 Of Our 4-Part Article: AlsPlumbing.com Part-1 Of 4 Knob And Tube Electrical Wiring
Part-2 Discusses:
- Additional Ways To Spot K&T Wiring (other than in the basement or attic).
- Where the House Wiring connects to Power Company’s wiring (with Overhead Power Company wires – not underground).
- The home has a Fuse Box. Details about what you’re looking for are within this Part-2 (scroll down).
WHY K&T Wiring Is No Longer Safe.
Here’s What Knob And Tube Wiring Looks Like
Image Source: YouTube Embedded Video Link
TIP: If You Don’t Have Easy Access To A Basement Or Your Attic — We Discuss More Ways To Help Spot K&T Wiring At The Beginning Of Part-2.
Ways To Help Determine If Your Home Has K&T Wiring
This YouTube Video Discusses An Above-Ground Electrical Service Drop. It’s Where The House’s Wires Connect To The Power Company’s Wires.
Image Source: YouTube Embedded Video
SHOWN: Power Company Wire’s (white) Connected To House’s Wires (black) — At The Above-Ground Electrical Service Drop.
1. The Size Of House’s Wires — Where They’re Connected To The (above ground) Power Company’s Wires.
K&T wiring has a 60-Amp capacity — so the house’s wires are much thinner than a home with 100-Amp Service (or higher). See Photo Links Just Below.
A. Click Below To See The Power Company Connection To A Home — With 60-Amp Electrical Service. The home’s wires (coming from the metal pipe) are THIN.
Service Connection To A Home With 60-Amp Electrical Service
If Link Doesn’t Work, Copy This Into Your Browser: https://www.google.com/search?q=old+home+electric+service+drop&tbm=isch&ved=2ahUKEwiM2v_O-Zf9AhWW0ckDHePVAOUQ2-cCegQIABAA&oq=old+home+electric+service+drop&gs_lcp=CgNpbWcQA1CiCViBQWDbRWgBcAB4AIABQogB4ASSAQIxMZgBAKABAaoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=sQjtY8y9BJajp84P46uDqA4&bih=460&biw=951&hl=en#imgrc=UWgSy0s-qD-hoM
B. Click Below To See A Power Company’s Connection For A Home With 100-Amp (or Higher) Service. The home’s wires (coming from metal pipe) are Thick.
Service Connection To A Home With 100-Amps (or higher) Electrical Service
If Link Doesn’t Work, Copy This Into Your Browser: https://www.google.com/search?q=home+electric+service+drop&tbm=isch&ved=2ahUKEwiKgu3W95f9AhX72skDHf_mA6UQ2-cCegQIABAA&oq=home+electric+service+drop&gs_lcp=CgNpbWcQA1DWLVi0V2CvWmgAcAB4AoABcIgB0xySAQQ2MS4xmAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=qAbtY4qOKfu1p84P_82PqAo&bih=460&biw=951&hl=en#imgrc=uqP4ZVaC_GPpJM
2. The Home Has A 4-Fuses Fuse Box
TIP: If The Fuse Box Has More Than 4 Fuses — It Still May Be Connected To Original K&T Wiring + Additional Circuits That Were Added Later.
See Image Just Below: An earlier 4-Fuses Fuse Box Indicates K&T Wiring. It’s A 60-Amp Fuse Box.
Shown Below: A 4-Fuses Fuse Box — Was Installed With Knob & Tube Wiring
Shown: 4-Fuses Fuse Box — For K&T / 60-Amp Wiring
Image Source: YouTube Embedded Video Link
As Shown In the Fuse Box Above, without an electric kitchen stove
Typical K&T Wiring (without an electric kitchen stove) Had 4 Circuits:
- The kitchen had One 20-Amp Circuit
- All ceiling lights (throughout the house) were wired into One Circuit. That circuit was typically 10-Amps.
- There were 2 Circuits for Electrical Outlets.
- One circuit was typically 20-Amps.
- The other circuit was typically 10-Amps.
- Total Amps = 60.
How To Determine The Amps Capacity Of The Electrical Service
Shown Below: A 12-Fuses Fuse Box. It May Have Been Installed Later — With Existing Knob & Tube Wiring Connected To It.
TIP: If Additional Circuits Were Added Later — The Fuse Box Had To Been Upgraded To A Higher Capacity.
TIP: If More Than 4 Round Fuses Are In Service —
It’s Possible The Home Has (ungrounded) Early Modern Wiring — Installed In Some Homes Built Between 1950 — 1965.
TIP: Early Modern Wiring Has Cloth Outer Insulation. Today’s Wiring Has PVC (flexible plastic) Outer Insulation.
TIP: Early Modern Electrical Wiring Needs To Be Replaced Too — Due To Its Cloth Wiring Insulation AND Not Being Grounded.
TIP: To Understand All The Details About Your Home’s Electrical Wiring — Have A Licensed Professional Perform An Inspection.
Shown: 12-Fuses Fuse Box — For K&T Wiring/60-Amp Service + Additional Added Circuits Added.
OR Early Modern (not grounded) Wiring/100 Amp Service.
Image Source: YouTube Embedded Video Link
Image Source: Amazon.com Link
Both Early Modern Wiring & Today’s Wiring Are Visible Just Below
Image Source: YouTube Embedded Video Link
Shown: At The Bottom (of the (larger/upper Fuse) Box — You Can See Wiring With (silver) Cloth Insulation. That’s Early Modern Electrical Wiring.
Shown: At The Top (of the smaller/lower) Electrical Box — You Can See Today’s Wiring — It Has (black) PVC Outer Insulation.
Today’s Electrical Wire (often called: “Romex”)
Has 3 Separate Wires (Black = hot // White = neutral // (Uninsulated = ground wire)
They Are Grouped Together — Inside An Outer Layer Of Insulation (the outer layer’s color indicates the amperage it can carry).
Shown Below: Today’s Electrical Wiring
Image Source: Amazon.com Embedded Link
3. How To Determine If K&T Wiring Is Inside Walls
TIP: You Can Use An Infrared Heat Device — To Determine If There Are 2 Separate Electrical Wires Inside Walls
(like in the upper right-hand image just below).
K&T wiring’s hot & neutral wires are separated by several inches — to ensure they can cool properly within open air.
Today’s electrical wiring has 2 insulated wires – plus an uninsulated wire (the ground wire) inside a PVC (flexible plastic) outer jacket.
Shown: The YouTube Video Below Has An Infrared Image Indicating K&T Wiring (the 2 wires are separate).
Image Source: YouTube Video Embedded Link
How To Check For K&T Wiring In Walls With A Modestly-Priced Heat Sensing Device
Infrared-Image Devices are expensive. You can also determine if there are 2 separate wires with an Infrared Thermometer (shown below).
Image Source: Amazon.com Embedded Link
Click On Image To; See The Device, Read Details, or Purchase From Amazon.com
Note: This device doesn’t show an image. It only shows the temperature of what it’s pointed at.
TIP: To Check For K&T Wiring Inside A Wall:
- Turn off all electrical devices plugged into outlets.
- Connect a high electrical-demand device (like a portable heater set to medium) to the outlet.
- Wait 10 minutes.
At The Outlet:
- Slowly move the thermal-device around all 4 sides of the outlet — until you find where it’s registering more heat (coming from electrical wires inside the wall).
- Once you find a wire, slowly move the device left & right And up & down — to determine if there’s a 2nd warm wire nearby.
- If you detect a 2nd warm wire a few inches away — it’s K&T wiring.
TIP: If you prefer to see the actual image (like in the YouTube Video image above) — you can purchase a Thermal-Image Device.
TIP: You can also buy a Thermal-Image Device that connects to Apple or Android Smart Phones.
These devices are available from Amazon and many other retailers.
Because they don’t have buyer satisfaction ratings (on Amazon) — we can’t confidently suggest a specific brand or model.
4. Ungrounded Electrical Outlets
- If these outlets are present — your electrical service is not grounded. Based on the age of the home, ungrounded outlets indicates K&T wiring.
- If the home was built between 1950–1965 — it may have Early Modern Electrical wiring — that wiring isn’t grounded either.
Note: Early versions of modern electrical wiring were also not grounded.
In 1962 — the National Electrical Code (NEC) Began Requiring Grounded Outlets In Kitchen & Baths.
On 1/1/1971, The NEC Began Requiring All Home Outlets To Be Grounded.
Most (if not all) homes built after 1975 likely have grounded outlets throughout the home.
Note: State and Local laws may not have required electrical wiring at the same time the NEC did.
Shown: (3 holes) Grounded Electrical Outlet
Image Source: Amazon.com Embedded Link. Click On Image For Details.
TIP: The Ground Wire Connection Is On The Lower Left Corner Of The Outlet. It’s Painted Green.
TIP: If You See This Type Of Outlet In A Home — The Electrical System Is Likely Grounded.
TIP: Seeing This Type Of Outlet In A Home — Doesn’t Guarantee The Electrical System Is Grounded. It could simply be a replacement outlet.
Push-Button Light Switches
Images Source: Amazon.com Embedded Link
When K&T Wiring Was Originally Installed — Push-Button Light Switches Were Installed.
Ungrounded (outlets) Porcelain Light Fixtures
If you don’t see the (rounded-bottom) slot below the 2 (flat) slots — It’s not a grounded porcelain light fixture.
Why Knob & Tube Wiring Is No Longer Safe
Top Safety Concerns About Existing Knob & Tube (K&T) Wiring Still In Use.
TIP: Few (if any) Home Insurers Will Write A Policy On A Home With K&T Wiring.
TIP: Most (if not all) Mortgage Lenders Won’t Write A Mortgage On A Home With 60-Amp Electrical Service.
- K&T wiring is At Least 68 years old (last installed around 1955) AND Up To 143 years old (first installed in 1880).
- K&T wiring is not grounded. This may lead to possibly catastrophic electrical shock– in the event that any part of a short-circuit is touched.
- K&T wiring’s insulation is badly degraded due to age & exposure to heat.
- K&T insulation is either asphalt-saturated cloth (earlier versions) OR rubber (later versions).
- The asphalt-saturated cloth insulation is a Fire-Accelerant (due to the asphalt).
- The rubber insulation becomes brittle due to heat and age. In some cases the insulation falls off of live wire(s) — see 2nd image below.
- If insulation is missing, touching an exposed wire — can cause possibly catastrophic, electrical shock.
- With insulation that is badly degraded or missing — an Arc-Fault can occur (electricity jumping from one wire to the other) within the wire.
- Most of K&T wiring is separated by several inches BUT there are many locations where wire-splices are located (coupling 2 or more wires together).
Original K&T Wire Splices
- Original K&T Wire Splices (joining 2 or more electrical wires together) — were twisted, soldered, and then wrapped with cloth or rubber tape.
- Wire splices are at high risk of creating an Arc-Fault — due to degraded insulation.
- An Arc-Fault can set the insulation on fire — and that fire sets the house on fire.
- As Compared: Today’s homes’ wire splices are inside a Junction Box — to guard against sparks flying if something goes wrong.
- If an Arc-Fault occurs inside a junction box — the likelihood of a wire fire causing a house fire is dramatically reduced.
Click Here To See A Typical Original K&T Wire Splice: Common Original K&T Wire Splice
(If Link Above Doesn’t Work — Copy This Into Your Browser:) https://www.google.com/search?q=knob+and+tube+wiring+rubber+insulation+missing+in+attic&sxsrf=AJOqlzVExz6j_R1A5BBAiwXBRTC145ig5w:1675097769216&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiEzv274e_8AhUPkGoFHWqkBSIQ_AUoAXoECAIQAw&biw=960&bih=468&dpr=2#imgrc=qCP2m2pualhfjM
This YouTube Video Demonstrates An Arc-Fault Causing An Electrical Wire’s Insulation To Catch On Fire
(At Time: 0:40 / 1:56).
Image Source: YouTube Embedded Video Link.
This YouTube Video Shows Missing Rubber Insulation On A K&T Wire — That’s Live With Electricity.
Image Source: YouTube Embedded Video Link.
SHOWN: Very Old (and unsafe) Electrical Wiring With Cloth &r Rubber Insulation.
Beginning In The 1960s: Higher Electrical Demand Required Today’s Modern Electrical Wiring Being Installed.
TIPS: The National Electrical Code (NEC) Devotes Article 394 – To K&T Wiring.
Copy The Link Below Into Your Browser To Read NEC Article 394:
https://up.codes/s/concealed-knob-and-tube-wiring
K&T Wiring Isn’t Illegal. The NEC Does Not Require Replacing K&T Wiring — (State or Local Laws May Vary).
The National Electrical Code (NEC) Allows Extensions Of K&T Circuits Up To 6 Feet – BUT Without Additional Outlets.
Due To Its Minimal Amps Capacity — K&T Wiring Has Likely Been Stressed Due To
Using Fuses With Too High Amerage — OR Bypassing Fuses Completely
Overheated wires damage the wires’ insulation.
To See A:
1-Amp Fuse: Copy This Into Your Brower:https://www.grainger.com/product/BUSSMANN-Plug-Fuse-1A-1DC08?opr=IDPPLARECS&analytics=PLAPDP
2-Amp Fuse: Copy This Into Your Brower: https://www.grainger.com/product/BUSSMANN-Plug-Fuse-2A-1CZ15?opr=IDPPLARECS&analytics=PLAPDP
3-Amp Fuse: Copy This Into Your Brower: https: https://www.grainger.com/product/6F466?gucid=N:N:PS:Paid:GGL:CSM-2295:4P7A1P:20501231&gclid=EAIaIQobChMI9e397YOT_QIVygitBh34KwA6EAQYASABEgLyVfD_BwE&gclsrc=aw.ds
As Compared – Today’s Electrical Devices Use:
- 12.5 Amps — 1500-Watt Hair Dryer OR Portable Electric Heater.
- 11 Amps 18,000 BTU Window A/C
- 6.5 Amps 18 Cubic Foot Refrigerator
- 5-15 Amps Washer
- 9 Amps 60-Inch TV
The Dangerous Ways That Some Home Owners Dealt With K&T Wiring’s Limited Amps Capacity
- Some people used much larger Amps fuses — so fuses wouldn’t blow.
- Today, 30-Amps Fuses seem to be the largest. We don’t know if larger fuses were once available.
- K&T wiring is rated at 20-Amps for electrical outlets.
- A 30-Amp Fuse allows s 1-1/2 times as much electricity into K&T circuits — than the wire can safely carry.
- This stressed the wiring — well beyond what it was designed for.
- Worse Yet: Some people bypassed fuses altogether — allowing any amount of electricity into the wiring.
- This caused house fires.
- This author knows how this was done — but won’t describe it.
As Compared:
- Today’s homes typically have 100-Amp / 12,000 Watts & up to 200-Amp / 24,000 Watts Electrical Service (some homes have even higher amperage service).
- All-Electric homes often have higher amps electrical service — due to electric heat & electric water heater.
- Today’s Homes have 20 to 42 circuits.
- The minimum circuit size = 15 amps.
TIP: If You Have A Fuse Box Blow
Did You Know You Can Buy (15-Amp & 20-Amp) Reusable/Resettable Circuit-Breaker-Type Screw-In Fuses?
Shown: 15-Amp Circuit-Breaker Style Screw-In Household Fuse
Click On Image To; View Product, Read Details, or Purchase From Amazon.com
Images Sources: Amazon.com Embedded Links
Shown: 20-Amp Circuit-Breaker Style Screw-In Household Fuse
Click On Image To; View Product, Read Details, or Purchase From Amazon.com
Images Sources: Amazon.com Embedded Links
This Was Part-2 of our 4-Part Article About Knob & Tube Electrical Wiring. Al’s Plumbing — in Plano, TX provides Full-Service Plumbing; maintenance, repairs, and replacements for every plumbing component in your home. Al’s sells and installs gas and electric water heaters. Al’s is near your home in; Plano, TX; Allen, TX; Frisco, TX; and McKinney, Texas. We service all homes in southern Collin County, TX, and northeastern Dallas County, TX with no additional travel charges.
Call Al’s Today To Discuss Any Concerns Or Problems You Have With Your Home’s Plumbing.
We will arrange an appointment at your convenience.