DSH 492 Protection against access to live parts

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DSH 492 - a2 ~+ X$ ^: v& F& P( z  u+ m8 H

Protection against access to live parts % J; k5 Q8 v5 f- l" p+ F

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60335-1(ed.3)

9 U, Q0 K: n, d0 k! eStandard: IEC 60335-1:1991, 3rd Ed.
Sub clause: 8.1.4
% Q- F6 y! L0 l, K% r3 zSheet No. DSH-492
6 ^; S# Z$ Y' j: p' m8 vSubject: Protection against access to live parts
5 J: {8 U% Z# K( q, PKey words: - Functional earthing
Decision taken at 40th CTL meeting 2003
Question:
Is functional earthing for the secondary circuit of SELV transformers permitted?
  ?9 i/ L- L0 g( j& j5 d2 iRationale:
* X" ?$ f% n3 a- T% fSee question.
+ Q0 v- B& e1 s4 lDecision:
1) 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
example in whirlpool baths), in which case earthing of the secondary circuits are acceptable
6 e' B1 n4 l0 t2 f/ ^% ?1 Q- _; cif:
8 R* |* r- s! y# v$ o, B4 t9 Ya) the accessible parts of the secondary circuits are separated from the protective earthing
5 v* R# [$ Q- x  }0 w7 Fcircuit by at least protective impedance, or
b) the accessible parts of the secondary circuits are either directly connected to the protective
( w5 p8 R% N* w$ Q, ]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
test 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
  @8 a/ c" `8 a8 j: R3 }parts of the supply with insulation as specified for Class II construction.
2. See also the following figure.

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