This is Part-1 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.

This 4-Part Article Provides In-Depth Details About Knob & Tube

(K&T) Electrical Wiring — In Homes Built (up to) 1955

Part-1 Discusses:

  • What Knob & Tube wiring looks like.
  • 4-Fuses Fuse Boxes used with Knob & Tube wiring.
  • When electricity first became available in homes.
  • When K&T was being installed in homes — 1880 to as late as 1955.
  • When the first high-demand electric devices became available for homes.
  • When the first window a/c’s became available (1940).  Running 2 set the stage for 20-amp electrical circuits to become overloaded.

Click Here To Go To Part-2 Of Our 4-Part Article: Knob & Tube Electrical Wiring Part2Of4

Does Your Pre-1955 Home Have Knob & Tube (K&T) Wiring?

old house

Image Source: Shutterstock

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.

Knob & Tube Electrical Wiring was introduced around 1880 — the same time period when electricity began becoming available in homes.  At that time, common household appliances were limited to; toasters, tea kettles, coffee percolators, and clothes irons, and a few years later the first home refrigerator became available (it used 475 watts).  These devices didn’t (individually) draw much electricity.  4 And, if too much electricity passed through a circuit, a fuse would blow.

K&T wiring gets hotter than modern wiring.  This is why the two wires are separated by up to several inches, to ensure they can cool in the open air.  Because of the concerns about the heat the wires generated — where K&T electrical wiring ran through lumber, it went through a ceramic “Tube” (inserted into the lumber).  At other locations, where K&T wiring was supported by lumber — a ceramic “Knob” was used.  The knob was attached to the lumber, and the electric wire was held in place between the upper and lower parts of the knob.  This kept the (sometimes) hot wires from charing wood or perhaps setting the wood on fire.

When Originally Built — Homes Built As Late As 1955 Had Knob & Tube (K&T) Electrical Wiring.

TIP: Closer to 1950 many homes began using an early (ungrounded) version of modern electrical wiring.  An electrical inspection determines which wiring your home has.

TIP: Many older homes have been rewired — an electrical inspection can determine if your home has been rewired.

4-Fuses Fuse Boxes Used In Early Knob And Tube Wired Homes

Early K&T wiring provided only 4 Circuits For The Entire House.  Typically; The Kitchen had 1 circuit.  If it had an electric stove — the kitchen had 2 circuits. The Ceiling Lights (for the entire house) had 1 circuit, The Outlets (for the entire house) had 2 circuits (w/o an electric kitchen stove) OR  The Outlets (for the entire house) had only 1 circuit (with an electric kitchen stove).   K&T electrical service was 60-Amps.

Today’s (not electric heat) homes have 100, 150, or 200-Amps electrical service (some have higher amps).  All-Electric homes (2/3 of Texas homes are all electric) have higher total amperage needs.  A 2,000 SF home in Dallas, TX requires a 36,000 BTU Electric Furnace — that needs 30 amps.  A 4,000 SF home requires a 60,000 BTU Electric Furnace that needs 50-amps.  Today’s all-electric homes require 200-amps electrical service (or higher).

Shown Below Is A Common 4-Fuses Fuse Box


To Skip This Section — Scroll Down To The Next Double Lines.

Some History About Electricity Becoming Available Throughout The U.S.

At First, K&T Was The Only Wiring Available — And It Was Safe When First Installed. 

In 1882, Thomas Edison helped form the Edison Electric Illuminating Company of New York — offering home electricity to parts of Manhattan, NY.  Thomas Edison’s Pearl Street Station (located in the financial district of Manhattan) inaugurated electric service in September 1882.    In 1895, the first large-scale electricity generation project was installed at Niagra Falls in New York.  Some of its output went to Buffalo about 20 miles away.   During this time the only home electrical wiring for homes was K&T.

The History Of When & How The U.S. Became Wired For Home Electricity:

  • The U.S. The Great Depression occurred FROM 1929 (Stock Market Crash in Oct) TO 1939.
  • In November of 1932, President Franklin D. Roosevelt was elected President (for the first of four terms).
  • By March 1933 — 25% of the workforce was unemployed, and almost every bank had closed.
  • When Roosevelt took office in 1933, he acted swiftly to stabilize the economy and to provide jobs and relief to those who were suffering.
  • Roosevelt created “The New Deal” —  a series of Programs and Projects to create jobs and restore prosperity to Americans.
  • Over the next 8 years, the Federal Government instituted a series of projects and programs that would create or improve America’s infrastructure.
  • These were known as “New Deal” Programs.

Some Of The Most Well-Known “New Deal” Programs:

  • The Rural Electrification Act (REA) — brought electricity to rural areas in the U.S.
  • The Tennessee Valley Authority (TVA) — built hydroelectric dams in the Tennessee Valley area — to control flooding and provide electricity.  Today, TVA is the largest public power company in the United States.
  • The Security & Exchange Commission (SEC) — was implemented to; Protect Investors, Maintain fair, orderly, and efficient markets, & Facilitate capital formation.  The SEC was implemented to prevent another stock market crash like that in October 1929.
  • The Work Program America (WPA) — built infrastructure such as; bridges, airports, schools, parks, and water lines.
  • Civilian Conservation Core (CCC) — which was instrumental in creating the U.S. Public Parks System.

The Rural Electrification Act (REA)

In May 1936, The “Rural Electrification Act” (REA) was signed by President Franklin D. Roosevelt.  The REA was tasked with bringing electricity to all rural areas of the U.S.  Today the REA  was renamed “Rural Utilities Service”.

Before REA, in 1935, only 11% of U.S. rural areas had electricity. The main hurdle was that power companies were unwilling and/or unable to pay for the Electricity Transmission Wires required to carry electricity long distances — as the cost was too high to be practical for areas with limited populations.  Originally, private power companies suggested prices of $1,500–$2,000 (around $43,000 today) for each 1 mile of Electrical Transmission Power Line constructed.

The REA made low-interest loans available for large construction projects such as Power Lines & Power Plants.  By 1939, REA borrowers were building lines for around $825 (around $14,750 today) per 1 mile.

By 1943, 380,000 miles of power lines had been installed and were serving over 1 million rural customers.  The REA had lent $466 million for the installation of this Electricity Infrastructure.  The REA continued into the post-World War II era (WWII ended Sept. 1945).  By 1960 — 97% of U.S. rural areas had electricity.

electricity distribution lines with transformers

Image Source: Shutterstock

Shown: Electricity Transmission Wires (at top) & Electricity Distribution Wires (below).

This Is How Electricity Travels From Power Plants To Homes & Businesses

  • Transmission Wires (near the top of the photo above) carry electricity (at very high voltage) for long distances.
  • The Gray Cans (in the photo above) are “Step-Down” Electrical Transformers. 
  • These transformers step down (very high) voltage electricity (from the transmission wires) — to the 120 & 240 volts service needed by homes and businesses.
  • Distribution Wires (near the bottom of the photo above) route 120-Volt & 240-Volt electricity (from the Step-Down Transformers) into homes and businesses.

End Of Section About Electricity Becoming Available Throughout The U.S. 

In The Early Years Of Home Electrical Wiring — K&T Was The Only Choice  

old victorian house

Image Source: Shutterstock

In the 1980s — K&T Wiring began being installed in homes.

At The Begining — K&T Was Safe Because:

1. There Was Limited Electrical Demand.  In the early years; only lighting, fans, a washer, a refrigerator & countertop appliances used electricity.

2. The K&T wires were new.  Over time, the insulation became brittle due to age & the heat generated by the wires.  Overloading wiring created faster and more severe insulation degradation.

3. Fuse boxes protected the wiring.  And, with correct-sized fuses, the wiring was protected.  Up to 20-amp fuses protected the circuits for Electrical Outlets & Kitchen.

Shortly After Homes Had Electrical Wiring — High-Demand Electrical Devices Became Available

Electric Heaters

electric heater

Image Source:

3. In the early 1890s — the first portable electric heaters (built by General Electric) used glass light bulbs to generate heat.  Incandescent light bulbs create heat from 90% of the electricity used (the other 10% is light).  A 100-watt bulb produced 90 watts – or 310 BTU’s of heat.   Early electric heaters had 3-4 bulbs.

Four 100-watt light bulbs could produce about 1,250 BTU’s.   Watts / Volts = Amps — So, 400 watts / 120 volts = 3.3 amps.  Since K&T wiring’s typical outlet circuits were 20-Amps — the earlest electric heaters didn’t overload home electrical wiring.  And, if the homeowner was using the correct size fuses, the wiring was protected.

By the late 1940s coil electric heaters were available.  They likely used 1,500 /watts or 12.5 amps — so any single K&T circuit can handle ONE electric heater and have capacity for other electric devices to be running.  Running 2 1 coil electric heaters created 25 amps of demand — on a 20-amp ciruit.


Window Air Conditioners

window air conditioner

Image Source:

4. Around 1940 General Electric & Carrier introduced their first 6,000 BTU window air conditioner.  During 1947 (2 years after WWII ended) – 43,000 window air conditioners were sold in the US — and many of them went into homes with K&T wiring.

If the earliest window a/c used twice the electricity of today’s 6,000 BTU window a/c — it used 1, 200 watts, or 10 amps.  In many K&T-wired homes, outlets were served by 20-amp electric circuits. ONE early 6,000 BTU’s window a/c’s (on one circuit) could safely run — and have the capacity to run other electrical devices.

If TWO early 6,000 BTU’s window a/c’s were running — that circuit was at its maximum (safe) capacity — and running any other electric devices began overloading the circuit.    If the homeowner was using the correct, 20-amp fuses — a 20-amp fuse would blow to protect the wiring.  To Be Safe — the homeowner could reduce demand on that circuit.  In Reality — many homeowners would install a 25-amp or 30-amp fuse — to keep it from blowing.  Some homeowners chose to bypass the fuse altogether (it can be done but this author won’t say how).   This set the stage for K&T wiring to overheat, which damaged its insulation.

Click Here To See A Photo Of GE’s First Window A/C: GE’s First Window A/C.

Click Here To See A Photo Of Carrier’s First Window A/C: Carrier’s First Window A/C

Carrier’s Price Was $61.50.  The Price In 2022 Dollars = $1,275.00.



The First Refrigerators — Did Not Overload K&T Wiring 

  • The Kitchen typically had its own 20-amp circuit to serve the electrical demand of; refrigerator, clothes washer (often in the kitchen) & countertop appliances.
  • If equipped with an electric range — a 2nd, separate 30-amp circuit was required for it.
  • In 1918 — when DOMELRE brand was the first home refrigerator.  To accommodate K&T wiring, the DOMELRE refrigerator used 4 Amps (475 watts) of electricity.
  • This particular refrigerator kept its electricity demand low enough that K&T wiring could safely handle it.

Click Here To See An Advertisement For The DOMELRE Refrigerator (scroll down): DOMELRE Refrigerator Ad (scroll down)

If Link Doesn’t Work — Copy This Into Your Browser


  • The kitchen (w/o an electric range) had 1 separate circuit.
  • This left only 2 circuits for outlets — for the entire home (ceiling lights were all on one separate circuit).
  • The kitchen (with an electric range) required 2 separate circuits.
  • This left only 1 circuit for outlets — for the entire home.

As Compared To Today: Kitchens have a separate circuit for large appliances + 3 to 4 circuits for countertop appliances.  The laundry room has a separate circuit.


This was Part-1 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.