John Stokes asks about plug/socket maximum amperage for isolation and maintenance purposes and whether BS EN 60309-1 is the correct related standard. His question has been answered by the NICEIC (Theme - Fire, Safety & Security):
Question: What is the maximum amperage rating of a plug/socket that can be used for switching off in order to carry out mechanical maintenance?
I've noted that Regulation (Page 152) 537.3.2.6 states not exceeding 16A. However, Table 53.4 (Page 149) appears to state that a 32A plug/socket (or greater than 32A) can be used for isolation. The plug/socket standard quoted in this table is to BS EN 60309. BS EN 60309-1 covers, I think, interlocked switches. Is this standard for a socket that has a combined isolator?
Is there a difference between isolation and switching off for mechanical maintenance?
I found the above confusing, so there must be something I missed.
Answer: The table does not give indication for switching off for mechanical maintenance, which is a different concept to isolation. Isolation is the removal of electrical energy to reduce a shock risk where switching for mechanical maintenance is as it states and live conductors may still be present. A plug and socket outlet would normally achieve both functions.
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