This is Part-4 of our 4-Part Article — About Knob & Tube (K&N) Electrical Wiring’s Reactions To Increasing Amps Of Electricity.  It discusses K&T wiring’s reactions to increasing amps of electrical current.  Also provided are 2 examples of dangerously overloaded K&T 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.

PLEASE NOTE: Als Plumbing Does Not Provide Electrical Services. 

Click Here To Go To Part-1 Of Our 4-Part Article: AlsPlumbing.com Part-1 Of 4 Knob And Tube Electrical Wiring

Here’s What Knob And Tube Wiring Looks Like

Image Source: YouTube Embedded Video Link

K&T Wiring Reactions To Increasing Amps Of Electrical Current

As discussed in earlier parts of this article, K&T wiring is between 68 years and 143  years old.  It was installed in homes starting around 1880 and as late as 1955.  K&T wiring has Asphalt-Saturated Cloth or Rubber Insulation.  As compared, today’s wiring is insulated with PVC (flexible plastic) insulation.

K&T wiring’s Age & Insulation Materials are two of the top reasons it’s unsafe.  Another top reason is that K&T wiring’s capacity (to carry electricity) is far too low for today’s homes.  K&T wiring is rated at 60-Amps for the entire house.  Today most homes’ electrical systems are rated at 100 to 200-Amps.

Original K&T Wired Homes Had 4 Circuits. 

Total Amps For The Entire House = 60 Amps.

One 10 Amp Circuit For All Ceiling Lights.

One 20 Amp Circuit For The Kitchen.

A Two-Story Home Had:

One 15 Amp Circuit For Outlets (upstairs)

One 15 Amp Circuit For Outlets (downstairs).

This YouTube Video Shows (Likely An Original) K&T Wire Home’s Fuse Box.

Image Source: YouTube Embedded Video Link

Click On The White Arrow To View This Video

Inside The “Pull Outs” (with the half-round handle) — Are A Total Of Four 15-AMP Long Fuses.

Image Source: Amazon.com Embedded Link

SHOWN: 15-Amps Long Fuses Are For The “Pull-Outs”.

Click On Image To; View Product, Read Details, or Purchase From Amazon.com

Round Fuses Come In Several Amps Sizes.

Another, Often Overlooked, Danger With K&T Wiring — Exists At Ceiling Light Fixtures. 

Image Source: Shutterstock

Shown: Incandescent Light Bulb

• Ceiling Fixtures were not labeled regarding maximum light bulb wattage.
• As Compared — Today’s Fixtures Limit (incandescent) Light Bulb Wattage To 60.

• Ceiling light fixtures were often the only source of lighting in a room.  This led to high-wattage light bulbs being used.
• 90% of the electricity used by an incandescent light bulb — Generates Heat.  Only 10% generates light.
• A 100-Watt incandescent bulb creates nearly 350 BTU’s per hour.  150-Watts creates around 510 BTU’s
• Decades of heat generated by light bulbs causes the wiring’s insulation to become brittle — just above the light fixture.
• The light fixtures are made of metal.
• The combination of the metal fixture, and wiring with failing insulation, create a Short-Circuit Fire Hazard.

** Source: https://www.smartenergy.com/home-wiring-101/

For A Two-Story Home: The Upstairs Outlets’ Circuit — Is 15-Amps

This is common K&T Wiring:

• The Upstairs Outlet Circuit — Originates at the Fuse Box.
• From the Fuse Box — The 2 K&T “Lead Wires” head upstairs inside a wall.
• From The Wall — The K&T circuit’s 2 “Lead Wires” enter the attic.
• Inside the Attic — All upstairs outlets are spliced/connected to the 2 “Lead Wires”.

Click Below To See K&T Wiring With Lead Wires Spiced To Wires Going To Outlets:

K&T Lead Wires With Splices For Outlets Wires

(If Link Doesn’t Work — Copy This Into Your Browser  https://www.google.com/search?q=knob+and+tube+wiring+splice+inside+attic&tbm=isch&ved=2ahUKEwjP5uP79cz9AhXFOd4AHbJJApAQ2-cCegQIABAA&oq=knob+and+tube+wiring+splice+inside+attic&gs_lcp=CgNpbWcQA1DsBljJFWDdF2gAcAB4AIABTogBrgSSAQE4mAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=Z84IZI-XF8Xz-LYPspOJgAk&bih=468&biw=960#imgrc=qCP2m2pualhfjM

How A K&T 15-Amps Circuit Can Become Dangerously Overloaded

Unless the HVAC has been updated — most K&T wired homes have Radiator/Steam heat or a “Gravity-Feed” Furnace (no furnace blower).  With either of these heating systems — Central A/C isn’t an option.  NOTE: K&T wired homes have no insulation in the walls or attic.  During Summer: Many homeowners use Window A/Cs.  During Winter: Many homeowners use Portable Electric Heaters — draw even more electricity than window air conditioners.

Radiator-Steam Heat

Click Here To See A Gravity-Feed Furnace (can be; coal, heating oil, or gas): Gravity Feed Furnace

Just Below We Show:

A Summer Example — with Window Air Conditioners overloading the 15-Amp Circuit serving all outlets on the second floor of a two-story house.

A Winter Example — with Portable Electric Heaters overloading the 15-Amp Circuit serving all outlets on the second floor of a two-story house.

How Window A/Cs Can Dangerously Overload A 15-Amps K&T Wiring Circuit

And May Lead To A K&T Wiring Electrical Fire

Image Source: Amazon.com

SHOWN: 8,000 BTU Window A/C

Click On Image To; View Product, Read Details, or Purchase From Amazon.com

Window A/C:        

          BTU   AMPS

• 6,000    5.5 BTUs needed for a small bedroom (remember K&T homes have no insulation inside the walls or attic).
• 8,000    7  BTUs needed for a medium bedroom.
• 12,000  9  BTUs needed for a large bedroom.
• 18,000 11 BTUs needed for a living room or kitchen.  18,000 BTUs — is the largest window A/C that runs on 120-Volts.

• 3 Upstairs (8,000 BTU) A/Cs alone draw 21-Amps — on a circuit rated for 15-Amps.

• One of the biggest dangers of a Fuse Box is that all round fuses are the same size circumference — regardless of their amps capacity.
• The 3 upstairs A/Cs alone blow a 15-Amp & a 20-Amp Fuse.
• In response, the homeowner installs a 30-Amps Fuse.
• The 30-Amps Fuse — allows the circuit to carry up to double the electricity the K&T circuit is rated for and can safely handle.

• The Upstairs Bathroom’s Outlet — is likely wired into the upstairs outlets’ circuit.      (A downstairs bath is often wired into the kitchen’s circuit.)
• If a 1,500-watt hair dryer is running on high — it adds +12.5 amps of electricity demand to the upstairs circuit.

• The 30-amps fuse blows if the hair dryer is set to highest setting.
• To avoid this, the dryer is set to medium setting (1,000 watts & 8.5 amps)
• This reduces the total electricity demand to 29.5 amps — whenever the hair dryer & 3 A/Cs are running.
• When the hair dryer and 3 A/Cs are running — the circuit is carrying double the electricity it’s rated for and can safely handle.

• Overloading K&T Wiring Causes It To Get Very Hot.
• The Hotter The Wire — The Higher The Risk Of  K&T Wiring Catching On Fire. 

• Fire Departments responded to 46,700 electrical fires per year (during 2015-2019). **
• These fires caused an average of 390 deaths & 1,330 injuries each year.
• These fires caused an estimated $1.5 billion in property damage each year.

** Source:  https://www.nfpa.org/News-and-Research/Data-research-and-tools/Electrical/Electrical

A Real-Life Example — Multiple Window A/Cs Using Double The Amps Of Electricity A K&T Wire Could Carry

This Is A First-Hand Story — From the Electrician Company Shown Below In Source ***

“We worked in a home where the owner replaced every fuse with a 30amp fuse.  This was done years before us getting there and no fire had happened, yet.  We ended up rewiring the house, and the condition of the interior wiring was brutal. The insulation was completely cooked in some areas and missing in others.  The owner was running a bunch of window air conditioners, drawing double the amperage the wiring could handle.”

*** Source: https://www.kuhlmanelectricalservices.com/fuse-panel-frequently-asked-questions/  THEN Scroll Down To: “Q: Are fuse panels a fire hazard??”

How Portable Electric Heaters Can Dangerously Overload A 15-Amps K&T Wire — And May Lead To An Electrical Fire

Image Source: Shutterstock

SHOWN: 4 Bedroom Vintage Home

It’s The Coldest Time Of Winter

Image Source: Shutterstock

Shown: Portable Electric Heater

Remember K&T homes have no insulation inside the walls or attic.

• Each of 4 bedrooms has a portable electric heater set to high/1500 watts (x4) (6,000 watts / 50 amps total).

• Each of 4 bedrooms has an electric blanket set to high/150 watts (x 4) = 600 watts (6,600 watts / 55 amps total).

Because The Owner Bypassed The Fuse — Any Amount Of Electricity Can Run Through the 15-Amp K&T Wire serving the upstairs of a two-story home.

• In the upstairs bathroom — a hair dryer now runs on high/1500 watts — (8,100 watts / 67.5 amps total).
• In the upstairs bathroom — a portable electric heater runs on high/1500 watts — (9,600 watts / 80 amps total).

Image Source: Shutterstock

Shown: Handheld Hair Dryer With 500 / 1000 / 15000 Watts Settings.

• Since the upstairs bathroom is being used — another sibling turns on their hair dryer on high/1500 watts — 111,000 watts / 92.5 AMPS 
• Decades of Aging + Dramatically Overloading The 15-Amp K&T wire — has degraded its insulation.

• At 90+ Amps — the K&T wire gets red hot — At Time: 23:15 / 25:59 (in the video below).
• Electrical Arcing in the K&T wire occurs — At Time 23:45 / 25:59.
• The Electrical Arching causes the K&T wire to catch on fire — At Time: 23:45 / 25:59.
• The Electrical-Wire Fire — starts the adjacent 2×4 on fire — At Time: 23:50 / 25:59.

Image Source: Shutterstock

Shown: House Fire

IF YOU HAVE A FUSE BOX — Use Only The Maximum Amps Fuse The Wiring Can Safely Handle. 

If You Don’t Have Fuse Amperage Information On The Fuse Box — With Knob & Tube Wiring 15 Amps Is Typical For Electrical Outlets.

When A Fuse Blows — It’s Because Electricity Demand On That Circuit — Exceeded The Maximum Safe Level.

NEVER BYPASS FUESES — Doing That Creates A Fire Waiting To Happen.

NOTE: This experiment was done at the ground and in the open air.  The temperature of the air, during the experiment, was far lower than attic temperatures.

• In a home — wiring is inside walls and often inside the attic.
• In Dallas, attics’ temperature reaches 160 to 170 degrees during the year’s hottest days.
• TIP: Heat inside the walls or attic Is In Addition To –the heat being generated by the K&T wiring itself.

** Source: https://homeinspectioninsider.com/what-temperature-should-an-attic-be/

This YouTube Video Demonstrates K&T Wirings’

Reactions During Increasing Amps Of Electrical Current

Image Source: YouTube Embedded Video Link

• The K&T Electrical Wire demonstrated in the video above – is much the same as Today’s 14-Gauge wire — which is rated at 15 amps.

• At Time: 3:00 / 25:59 — The Wiring Is Carrying 15 Amps.  The narrator says: “I can barely detect any heat in the wiring.”  (At Time: 3:10 / 25:59)

NOTE: This indicates that K&T wiring can carry 15 amps (what it’s rated for) — without damaging its insulation.

• At Time: 4:15 / 25:59 — At 20 Amps.  The asphalt-saturated cloth (the narrator calls it: “rubber”) — insulation feels: “warm”.
• At Time: 6:25 / 25:59 — At 30 Amps.  The asphalt-saturated cloth insulation moves when pushing on it.
• At 30 amps, the wiring’s insulation is becoming affected by the heat generated inside the wires.

In Response To Blowing Fuses — Some Homeowners Bypassed Fuses.   

This allows any amount of current into the wire.

(The author knows how to bypass fuses, but won’t describe it.)

• At Time:   7:30 / 25:59 — At 40 Amps.  The asphalt-saturated cloth insulation becomes soft due to heat.
• At 40 Amps — the insulation is experiencing damage.

• At Time: 10:40 / 25:59 — At 50 Amps.  The rubber insulation comes off when touched.  Wire it too hot to hold onto.
• At 40 Amps — the insulation is experiencing damage that can cause an electrical fire.
• Missing Insulation Is One Of The Top Causes Of Electrical Arcing (electricity jumping through the air).

• At Time: 14:15 / 25:59 — The Wiring Is Carrying 60 Amps.  The rubber insulation is melting.  There is a “burning rubber” smell.
• At 60 Amps — the insulation is damaged so badly — that the wiring is unsafe and needs to be replaced.

• At Time: 17:15 / 25:59 — At 70 Amps.  The rubber insulation is smoking (smoke visible at At Time: 19:30/25:59).  Wire is too hot to touch.
• At 70 Amps — the insulation is damaged so badly that an electrical fire may start.

• At Time: 19:15 / 25:59 — At 80 Amps.  The rubber insulation is smoking heavily (At Time: 19:30/25:59).
• At 80 Amps — it’s fair to say the insulation is damaged so badly that an electrical fire is about to start.

• At Time: 22:15 / 25:59 — At 90 Amps (10,750 Watts).
• 1st: The K&T wire is glowing red — much like the coils inside a toaster.
• 2nd: The rubber insulation is nearly entirely gone.
• At 90 Amps — the insulation is damage so badly that an electrical fire will occur.

• At Time: 24:00 / 25:59 — There is Visible Arcing/sparking.  Arcing is one of the leading causes of electrical fires.
• The arcing is causing the nearby wood to become charred.
• Arcing is a major contributor to Electrical-Wire House Fires.

TIP: Arching is not limited to K&T wiring.

This was Part-4 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.