Rick, let's start with the general requirement per clause 1.7.8.1. The
requirement is "Unless it is obviously unnecessary, indicators, switches and
other controls affecting safety shall be identified or placed so as to
indicate clearly which function they control. Indications used for this
purpose shall, wherever practicable, be comprehensible without a knowledge
of languages, national standards, etc."
Does the switch in question affect safety? Since the switch performs a power
on/off function, I would say yes. Are the "on" and "off" positions of the
switch understandable without markings? Probably not, so some kind of
marking is required and the type is specified by clause 1.7.8. as the famous
"I" and "O" (or the push button symbol or standby symbol).
Is it allowed to mark a power switch that only switches one side of the
mains? Yes, the marking is permitted by clause 1.7.8.3 to be applied to "any
primary power switches."
Putting all of this together, the answer is yes, the marking is both
permitted and required on your power switch.
Richard Woods
----------
From: Rick Linford [SMTP:[email protected]]
Sent: Friday, April 27, 2001 12:25 PM
To: [email protected]
Subject: EN60950 (UL1950, IEC 60950) On off switch marking.
Hi All,
When a switch opens only one leg of the mains to control power to
equipment should it be marked with the "l" and "O"?
Background:
Three different engineers from three different NRTLs indicated it is
permitted, two even required it. A different engineer for one of the
NRTLs and two other respected individuals indicate it is prohibited.
It
will be interesting if members of this list will have the same 50/50
split or if there is a correct answer.
(single phase 100 to 240 VAC, 2A, 50-60 Hz, intended to be shipped
US,
Canada, EU and generally internationally)
To help, IEC 60950 (1999), section 1.7.8.3 Symbols, is shown below.
Where symbols are used on or near controls, for example switches,
push
button, etc., to indicate "ON" "OFF" conditions, they shall be the
line
l for "ON" and the circle O for "OFF" (60417-1-IEC-5007 and
60417-1-IEC-5008). For push-push type switches the symbol {line in
side
the circle} shall be used (60417-1-IEC-5010).
It is permitted to use the symbols O and l to indicate the "OFF" and
"ON" positions of any primary or secondary power switches,
including
isolating switches.
A "STAND-BY" condition shall be indicated by the symbol {line
breaking
the circle at the top} (60417-1-IEC-5009).
My bias was not included in the 50/50 statistics noted above but I
believe it is required.
Rick Linford
Regulatory Engineer
SonicWALL
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