Sometime ago i had a discussion with a colleague re: whether or not it was permitted to have 2 phases at a switch for what ever the reason, i believed it was legal as long as it was labelled, can anyone tell me if it is permitted or not, and where it makes mention?
Many thanks CW
2 phases at a switch?
Re: 2 phases at a switch?
Of course it's OK to have more than 1 phase in an enclosure - how else would 3-phase equipment work?.
I suspect what's meant is 2 different circuits present; and again the answer is "yes".
The follow-up question is whether para 4 of Clause 2.3.2.1 requires a "notice" simply for presence of more than one circuit.
The correct answer is "No"; as the requirement is for where there is equipment ("live parts")that is connected to more than one supply.
In most cases, eg multiple switch banks for commercial lighting, each item (switch) is connected to only one circuit.
Same for socket outlet plates with 'extra' switch, the switch can be on a different circuit from the sockets.
If the Clause was meant to apply to simple cases of multiple circuits; it wouldn't be worded the way it is.
The writers don't set out to create confusion; and they choose their words carefully -generally saying things as simply as possible.
The general rule is that if the same words are used, the same thing is meant (and vice versa).
This clause could have simply said: "If more than one circuit is present within an enclosure; a notice shall be fitted".
But it doesn't; so clearly something else was intended.
The wording is "live parts that connected to more than one supply"; and an example would be a source selection switch (normal power vs standby,
or where something is supplied via multiple paths such as manual / auto switching).
The point being to warn anyone working on the equipment that isolation may be more complex than normal.
Simple testing for "no live" may not keep us safe, if the other source switches on.
For simple cases of multiple circuits present; we're supposed to be trained professionals and be able to notice such matters,
and to ensure that the one(s) we want to work on have been isolated.
However EWRB have adopted a view that a notice is required every time there are multiple circuits present within the enclosure.
Therefore, since providing a "notice" is cheap & easy; would be wise to provide one anyway.
I suspect what's meant is 2 different circuits present; and again the answer is "yes".
The follow-up question is whether para 4 of Clause 2.3.2.1 requires a "notice" simply for presence of more than one circuit.
The correct answer is "No"; as the requirement is for where there is equipment ("live parts")that is connected to more than one supply.
In most cases, eg multiple switch banks for commercial lighting, each item (switch) is connected to only one circuit.
Same for socket outlet plates with 'extra' switch, the switch can be on a different circuit from the sockets.
If the Clause was meant to apply to simple cases of multiple circuits; it wouldn't be worded the way it is.
The writers don't set out to create confusion; and they choose their words carefully -generally saying things as simply as possible.
The general rule is that if the same words are used, the same thing is meant (and vice versa).
This clause could have simply said: "If more than one circuit is present within an enclosure; a notice shall be fitted".
But it doesn't; so clearly something else was intended.
The wording is "live parts that connected to more than one supply"; and an example would be a source selection switch (normal power vs standby,
or where something is supplied via multiple paths such as manual / auto switching).
The point being to warn anyone working on the equipment that isolation may be more complex than normal.
Simple testing for "no live" may not keep us safe, if the other source switches on.
For simple cases of multiple circuits present; we're supposed to be trained professionals and be able to notice such matters,
and to ensure that the one(s) we want to work on have been isolated.
However EWRB have adopted a view that a notice is required every time there are multiple circuits present within the enclosure.
Therefore, since providing a "notice" is cheap & easy; would be wise to provide one anyway.
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