Alternative supply change over switch location

[Dan L]

If the changeover switch is not being used as the main switch but is additional is it compliant to be line side of main switch?

7.5.8.1 and 2.3.3.1 suggests to me all installation must be controlled by main switch with no acception to changeover switch that I can see.

The relevant figures 7.2 and 7.3 don't show separate main switch.

Or by default would a line side changeover switch become the main switch and the original main switch become an isolator. This will not always be so easy to just re lable as such with Controlled night main from meter going direct to original main switch.

[AlecK]

Not sure why you're looking at 7.5.8.1; as that clause relates only to ELV.
7.3 is the directly relevant clause

An installation can have several "main switches".

There can be other switches either upstream or downstream of the "main switch(es)"
A common example being the isolating switches in meter boxes that allow metering / load control equipment to be isolated for safety.
An other example is shown in Fig 7.1; which is primarily about the arrangement of the several "main switches" that may be required,
but which also shows bus tie and other switches upstream of the 'main switches".

Figs 7.2 & 7.3 don't show any main switches,;as they are not about "main switch" requirements.
They're about changeover switch requirements.
If done at a MSB; it may be that the c/o is also the "main switch" for both normal and alternative supplies . Or not.
If done at a DB; it can't be the main switch for normal supply, but could be for the alternative supply. Again, or not.
Point being that the main switch requirements and the changeover requirements apply separately.
Whether we use one device for more than one function is up to us.

A Fig will always be consistent with all requirements; but doesn't always show all of them.
Generally they will show the simplest config to illustrate the particular requirement.


If you are dealing with a genset as alternative supply, you need the additional guidance of '3010";
both the (cited) 2005? edition and the 2017 edition.

If the alt supply is from a non-genset source; 7.3 still applies and the guidance on "3010" is still relevant.

[Dan L]

Sorry not sure what happened with 7.5.8.1

Thanks for clearing that up.

Attached photo that shows some good example of c/o switch and main switch location.

Thanks