Most household (consumer) appliances are what is called "Double or
Reinforced Insulated". This means that there are 2 (or more) layers of
insulation between the Hazardous voltages and the user. Total reliance is
placed on this insulation. These are, in safety parlance, called a Class
2 product. It can usually be idetified by the fact that the input
connector has only a Line and Neutral.
On the other hand, A Class 1 product has three pins on the connector, Line,
Neutral and Ground. The ground is used to tie parts of the assembly to
earth. That way, if there is a failure, the path for the fault current is
to earth via the ground pin and not the user. Reliance is placed on this
ground pin for protection. Testing is performed to assure that this is a
reliable connection.
However, please note that even though a Class 1 unit has a ground pin for
protection, there are usually parts in the product that have Double
Insulation (i.e. Transformer).
Daniel W. Mitchell
Product Safety Engineer
Condor DC Power Supplies, Inc.
"Ken Javor" <[email protected]> on 11/30/99 03:51:52 PM
To: [email protected]
cc: (bcc: Dan Mitchell/CondorDC)
Subject: safety ground wire
What determines whether equipment gets a green wire or not? TVs, toasters,
handheld hair dryers and just about anything for home use get two wire
power
cords. Computers and other ITE get three wire cords. Is the distinction
commercial vs. residential (class A vs. Class B)? It doesn't seem purely
safety related, since a metal toaster would appear to be more prone to
dangerous electrical faults than a doubly-isolated all plastic handheld
hair
dryer. What is the rule here?
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