13 August 2018

Electric Heating Elements

Oven Repairs in Port Elizabeth. South Africa

Heating Elements are used in all kinds of appliances. Fridges has them to help defrost excessive ice condensation. Washing machines use an element to heat up the laundry water. Tumble dryers use heating elements to heat up the air that blows through the turning drum and we also use heating elements to make a hot cup of java with a urn or kettle.


Defy bake element

In this post I am going to chat mainly about the elements used in Stoves and Ovens.
 
How do an elements work
Electric current flows through coiled resistance wire - the resistance causes the wire emanates  heat.


How an heating element is made


It is basically electricity passes through a tub.
  • The outer layer is made from copper or stainless steel that holds everything in places
while emanating heat.
  • Insulating layer-  middle part made out of ceramic that conducts heat but not electricity.
insulates the outer layer and resistant wire from each outer.
This white powder is not poisonous but can change the taste of food.
  • Inner section -  Inner section is a coiled resistance wire (made from 80%Nickel & 20% Chromium)
which conducts electricity and generates heat.
Broken defy bake element


Electrical heating elements are made to withstand high temperatures


There are many different elements with various wattage output. Watts (energy) is just a term they use
to describe the current flow(usage). One watt is defined as the current flow of one ampere with
voltage of one volt.
Huh ! don’t worry for the average person this is useless information. Just remember the higher the
watts of your kettle or Urn elements the faster it will boil the water.
Power struggle - Amps Volts and  Ohms in a heated debate


Reasons why Heating Elements fail


  1. Bad ventilation - It is common for people to use aluminum foil or the flat tray that comes with
the oven and slides into the side of the oven as a drip tray. Big mistake! This pan should only
be used with your thermofan settings or in the middle of the oven right underneath the roast.
“But the book says!” I know but trust me on this.


When this tray is positioned at the bottom of the oven just above the bake element, the tray
acts as a barrier by trapping the heat, preventing the heat from reaching the thermostat. In
this trap-barrier the temperature is much higher than that of the top oven section. The
thermostat probe is normally installed in the top section or middle section of the oven
(because hot air rises).


This little boo boo is the single biggest reason why bake elements fail but the manufacturer's
has realised their mistakes and the new spill trays has vent holes on the sides so the hot air
can rise.


  1. Overheating -   Due to bad Thermostat control (not the same as when you have poor ventilation
as described above). Severe overheating is normally caused by a thermostat that is busy failing.
The element gets extremely hot before it cools down. Sometimes this extreme heating can cause
deformity on the element, resulting a shorter lifespan of the element.
3. Oven door seal faulty -   a bad door seal will give you a combination of the first two points.

The hot air inside the oven escapes passed the damaged oven gasket. Again because hot air
rises it is very important that you have a good seal on the top section of the oven. Hot air leaking
causes the heating elements to work much harder and longer to maintained preset temperature.


4.Manufacturing - Manufactures are under constant pressure from the east to supply cheaper.
The competition forces them to cut corner by manufacturing with cheaper and  inferior product.Cutting on labor and staff is affecting the end results.
5.General operating errors

Overused - Domestic stove and oven elements are not the same as and Industrial oven.
Domestic ovens can only be used for unlimited periods of time per day. A household oven maximum working time is between 4 to 5 hours per day.  Using a heating element for extended periods of time at high periods will cause the element to deform and blister.

Spillages -  Elements that get douses with liquids that from a leaking pan could cause
 the element to cool down too fast in sections. This could cause the element too blister and  explode. 

Power fluctuation - Constant high power fluctuation causes small “ding’s” (damages) to  the
resistant wire and electronic components in the oven. This phenomenon is called “Electronic rust”.
When looking at AC power flow on a oscillator-screen one can see the power in waves going up and
down.

The signs of excessive Power fluctuations is the same as one power surge. It is just that the damaged
happened over a time period.

Elements are made to withstand high temperatures. Domestic elements range from 50 degrees to 300
degree Celsius.  


Once switch-on elements go full blast - there is no half heat and that’s why you need a controller like a
thermostat to regulate heat emanation of the element.


If you want more information or would like to add, leave a comment below or send me a email

Happy bakking

www.pinepienaar.info