DSH 492 Protection against access to live parts

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DSH 492 4 u/ ~. T* F: k% ^2 o

Protection against access to live parts

8.1.4 / P, [  g3 J) l4 {4 Z2 x

60335-1(ed.3) 9 z: j( I8 h3 C3 A0 x

Standard: IEC 60335-1:1991, 3rd Ed.
  a. ~% b5 p* U& D2 x0 e7 HSub clause: 8.1.4
Sheet No. DSH-492
Subject: Protection against access to live parts
Key words: - Functional earthing
; ~- y: H) x+ z5 L4 \. O2 gDecision taken at 40th CTL meeting 2003
Question:
Is functional earthing for the secondary circuit of SELV transformers permitted?
+ }0 c4 k8 {  H- h; ]$ N, S; RRationale:
1 ]9 `; {# z# R0 O# r& i, ESee question.
7 H' ]3 a9 i4 T& M7 }4 H  zDecision:
/ s- {3 r3 X. F1) Earthing of secondary circuits of SELV transformers (PELV circuits) is acceptable in
general except when SELV is specifically required by the standard for a specific circuit (for
) L8 c' B( B9 ~7 Eexample in whirlpool baths), in which case earthing of the secondary circuits are acceptable
if:
a) the accessible parts of the secondary circuits are separated from the protective earthing
7 G0 i" H. b& L4 ^& Z7 b' H; Y5 ucircuit by at least protective impedance, or
; A7 ?* R. U9 a* X1 ]4 J( k' _b) the accessible parts of the secondary circuits are either directly connected to the protective
earthing circuit or are protected against accidental contact by insulation as specified for Class
III appliances or constructions, in particular the insulation shall be capable of withstanding a
& m( e* j: F  I5 ?  ttest voltage of 500 V AC for 1 min.
Accessible parts directly connected to the protective earthing circuit shall comply with the
requirements for protective earthing (see sub-clause 27.5) or shall be separated from live
parts of the supply with insulation as specified for Class II construction.
2. See also the following figure.

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