DSH 492 Protection against access to live parts
http://decisions.iecee.org/icons/ecblank.gif DSH 492
Protection against access to live parts
8.1.4
60335-1(ed.3)
Standard: IEC 60335-1:1991, 3rd Ed.
Sub clause: 8.1.4
Sheet No. DSH-492
Subject: Protection against access to live parts
Key words: - Functional earthing
Decision taken at 40th CTL meeting 2003
Question:
Is functional earthing for the secondary circuit of SELV transformers permitted?
Rationale:
See question.
Decision:
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
if:
a) the accessible parts of the secondary circuits are separated from the protective earthing
circuit by at least protective impedance, or
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
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
parts of the supply with insulation as specified for Class II construction.
2. See also the following figure.
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