grounding questions...

[Theo]

----- Original Message -----
From: René Schmitz <uzs159 at uni-bonn.de>
To: Ingo Debus <debus at cityweb.de>; <synth-diy at node12b53.a2000.nl>
Sent: Saturday, May 13, 2000 7:48 PM
Subject: Re: grounding questions...


>
> But as Tony already pointed out: classification of our homebrew devices is
> difficult, I guess most falls inbetween class 1 and 2 with a questionable
> safety.
>
> Bye,
>  René
>
I don't get this, the classification rules are plain simple.
For everyone who got confused here are some practical rules.
(I'am thinking mainly about the less experienced list members here)
Some details are omitted to keep things simple.

Class I:
-Minimum distance bedween the primairy sercuit (mains) and enclosure; 3mm.
-Minimun distance beween secondairy circuit and enclosure; 6mm.
-A classI or II transformer may be used.
-All conductive touchable parts must be grounded to the mains GND,
this includes the enclosure.
-Connectors don't have to be grounded, if a classII transformer is used.
-The device must have a mains connector with GND connection.

Class II:
-Mininum distance bedween primairy circuit and enclosure; 6mm.
-Minimun distance beween secondairy circuit and enclosure; 6mm.
-A class II transformer it used.
-The mains connector has no GND connection and is "one part" with the power
lead to the divice.
-Secondairy ground may be touchable.
-No grounding of touchable conductive parts is needed.

Just to be on the save side:
-A classII transformer is used.
-A double main switch classII is used.
-A primairy fuse is used, even if the transformer is short proof and a
double main switch is employed.

This information is by no means complete.
There are a lot "if and then's" that are not considered here.
When the Class I or II AND the "just to be on the save side" rules are
followed the device will qualify for the intended class.

For details see NEN3544 or equivalent DIN (sorry don't know the DIN number).
The 3mm and 6mm rules are a practical implementation from the test voltages
rated in the NEN norm.
The UK norm may slightly differ from that of the rest of europe.

The rules listed here are derivated from the safety chapter of a DIY book,
don't know which 'cause I've only a few zeroxes of the intresting parts.
Elector frequently prints a list with safety rules, so far I know these
compare to what I listed abouve.


Hope this will be usefull to someone.
Regards Theo