Hi Scott:


I have seen no safety standards or codes that specify which products must be 
Class I and which products must be Class II, except in the USA washers and 
dryers must be Class I.  As far as I know, the decision is that of the 
manufacturer.  I have been associated with a manufacturer who has made the same 
product both ways.  In my case, one of the factors in deciding Class I or Class 
II was cost (e.g., a 3-wire cord was more expensive than a 2-wire cord).  


I suspect a major factor is “momentum” of the manufacturer: we made it this way 
last time, and we know how to do it this way.  


A product with a grounding (3-wire) power cord is a Class I product regardless 
whether it has no accessible conductive parts.  Unlike a Class II product, a 
Class I product does not bear a marking attesting that it is Class I.  


Note that a Class I construction necessarily includes Class II construction, 
e.g., appliance inlet which is all-insulated.  We ignore the Class II 
construction portions of a Class I product.


I checked our electric kettle (which has accessible metal) and electric 
coffee-maker (which has the heater plate accessible metal).  Both are 2-wire.  
Neither has the double-insulated symbol.  Both are UL-certified.  


Best regards from beautiful snowy Bend, Oregon, USA,




From: Scott Xe <scott...@gmail.com> 
Sent: Tuesday, January 14, 2020 6:59 AM
Subject: [PSES] Class I vs Class II safety constructions


In terms of safety level, both constructions are given the equivalent 
protection against electric shock.  In electrical appliances, Class I is used 
most whereas Class II is employed in most electronic products.  Is there any 
background for such design route?


In some cases such as induction cookers, the enclosure is plastic/glass - no 
any internal metal part exposes to the outside surfaces.  The product is not 
marked with a double square symbol and comes with a 3-pin plug.  Why is this 
type of product not classified as Class II rather than Class I with the 
plastic/glass enclosure?


Thanks and regards,



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