|
Home > Archive > Electrical code Compliance > June 2006 > Double insulated products must not have an earth connection?
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
Double insulated products must not have an earth connection?
|
|
|
|
I want to make a microcontroller-based device that will switch mains inlet
power to two outlets. I will use optocoupled triacs to do this. There are
also buttons, an LCD and an RS232 port on the device.
I thought this meant I would be making a class II product because I want the
case to be plastic (cheaper and lighter). However, now I read that a class
II product *must not* have an earth connection.
This is a problem because the loads I want to control have earth
connections.
So I have a few questions:
1. Why can't a class II product have an earth connection?
2. The electrical loads (e.g. pneumatic valve) have earth connections, so I
must provide the earth from somewhere. If a class II product cannot have an
earth, does this mean I have to make a class I product? Or do I have to
find class II loads that don't need earth?
3. When I look around my house, I notice that some items like power boards
and timed outlets i) have plastic case, ii) have an earth connection, BUT
they are not labelled class II. So what class are they?
Thanks for any information.
| |
| charlieB 2006-06-01, 10:21 am |
| The type of case and the class of product are not related.
In class I equipment, protection against electic shock is achieved
through use of basic insulation and earthing those conductive parts
that can assume hazardous voltage levels if the basic insutation fails.
Class II equipment does not rely on the safety earth - it uses basic +
supplementary of reinforced insulation to provide protection between
hazardous voltages and accessible conductive parts
You can have an earth on class II equipment -though by definition it is
not "required"
You can have class I equipment in plastic case.
Note - the case has to act as a fire enclosure, that will place
restrictions on the type of material you use, but there are plenty of
fire retardent plastic cases out there.
Charlie
> I want to make a microcontroller-based device that will switch mains inlet
> power to two outlets. I will use optocoupled triacs to do this. There are
> also buttons, an LCD and an RS232 port on the device.
>
> I thought this meant I would be making a class II product because I want the
> case to be plastic (cheaper and lighter). However, now I read that a class
> II product *must not* have an earth connection.
> This is a problem because the loads I want to control have earth
> connections.
>
> So I have a few questions:
> 1. Why can't a class II product have an earth connection?
you can have one - but be definition, it is not required
> 2. The electrical loads (e.g. pneumatic valve) have earth connections, so I
> must provide the earth from somewhere. If a class II product cannot have an
> earth, does this mean I have to make a class I product? Or do I have to
> find class II loads that don't need earth?
> 3. When I look around my house, I notice that some items like power boards
> and timed outlets i) have plastic case, ii) have an earth connection, BUT
> they are not labelled class II. So what class are they?
>
> Thanks for any information.
| |
| charlieB 2006-06-01, 10:21 am |
| The type of case and the class of product are not related.
In class I equipment, protection against electic shock is achieved
through use of basic insulation and earthing those conductive parts
that can assume hazardous voltage levels if the basic insutation fails.
Class II equipment does not rely on the safety earth - it uses basic +
supplementary of reinforced insulation to provide protection between
hazardous voltages and accessible conductive parts
You can have an earth on class II equipment -though by definition it is
not "required"
You can have class I equipment in plastic case.
Note - the case has to act as a fire enclosure, that will place
restrictions on the type of material you use, but there are plenty of
fire retardent plastic cases out there.
Charlie
> I want to make a microcontroller-based device that will switch mains inlet
> power to two outlets. I will use optocoupled triacs to do this. There are
> also buttons, an LCD and an RS232 port on the device.
>
> I thought this meant I would be making a class II product because I want the
> case to be plastic (cheaper and lighter). However, now I read that a class
> II product *must not* have an earth connection.
> This is a problem because the loads I want to control have earth
> connections.
>
> So I have a few questions:
> 1. Why can't a class II product have an earth connection?
you can have one - but be definition, it is not required
> 2. The electrical loads (e.g. pneumatic valve) have earth connections, so I
> must provide the earth from somewhere. If a class II product cannot have an
> earth, does this mean I have to make a class I product? Or do I have to
> find class II loads that don't need earth?
> 3. When I look around my house, I notice that some items like power boards
> and timed outlets i) have plastic case, ii) have an earth connection, BUT
> they are not labelled class II. So what class are they?
>
> Thanks for any information.
| |
| Andrew Gabriel 2006-06-04, 10:21 am |
| In article <1149164410.796716.150870@h76g2000cwa.googlegroups.com>,
"charlieB" <charlie_on_the_net@hotmail.co.uk> writes:
> The type of case and the class of product are not related.
>
> In class I equipment, protection against electic shock is achieved
> through use of basic insulation and earthing those conductive parts
> that can assume hazardous voltage levels if the basic insutation fails.
>
> Class II equipment does not rely on the safety earth - it uses basic +
> supplementary of reinforced insulation to provide protection between
> hazardous voltages and accessible conductive parts
>
> You can have an earth on class II equipment -though by definition it is
> not "required"
> You can have class I equipment in plastic case.
I suspect this varies by country. I see a number of things in the
US which are double insulated, which would not come close to being
accepted as double insulated in Europe.
--
Andrew Gabriel
|
|
|
|
|