400v at switch

[wreck-it-steve]

in my industrial unit I have a 2 gang MK outdoor switch powering two sets of lights...

the two sets of lights are fed from two different breakers and such are on two different phases....

is this safe? there will be 400v at the switch!!

 

[Adam_151]

Put a 400v sticker on it. Or label the switches with circuit/phase references eg. 7L1 and 7L2. It is then clear to anyone working on it that there is more than a single phase present

 

[sparkwright]

Label is a good idea.

Or if you're still worried, get a competent electrician to fit two seperate single gang switches, seperately labelled to be on the safe side.

 

[wreck-it-steve]

but its perfecly normal/safe/complient to have a switch like this (even if its outdoors)?

 

[Lectrician]

Perfectly acceptable.

 

[PBC_1966]

Re the labeling, the IEE Wiring Regs./BS7671 have gradually relaxed the requirements over the years anyway. Fifty years ago a label warning of the voltage present inside any enclosure was required for anything over 250V. That was revised to requiring such a label only where voltages in excess of 250V would "not normally be expected," however one wishes to interpret that (expected by whom?). The latest revision a few years ago scrapped that requirement and refers only to the maximum voltage with respect to earth rather than the voltage which may be present between any two points within the enclosure, so even with 415V between phases or 480V between poles within the same switch box, no label is required, whether "normally expected" or not.

 

[333rocky333]

514.10 was only introduced 7 years ago not 50 years ago and it refers to nominal voltage over 230 volt, so unless the amendments to the 17th changed things, theres no longer mention of voltage to earth hence a label may be needed.
Hopefully someone with the latest book can clarify

 

[securespark]

There used to be a requirement that if two outlets on two different phases were within arms' reach of each other, they had to be labelled to warn of the presence of 415V.

 

[conny]

Why not label it anyway? It would certainly help to identify where it is fed from should a fault develop.

 

[PBC_1966]

514.10 was only introduced 7 years ago not 50 years ago and it refers to nominal voltage over 230 volt, so unless the amendments to the 17th changed things, theres no longer mention of voltage to earth hence a label may be needed.
Hopefully someone with the latest book can clarify

The 13th edition specified a warning label for the presence of medium voltage in any enclosure, whether between conductors or from any conductor to earth. The 14th edition (1966) relaxed that requirement to require the label only where medium voltage would "not normally be expected." The change to specifying the voltage only to earth rather than to earth or between conductors was much more recent,although I can't pinpoint the precise revision (16th or 17th edition?). Perhaps it was realized that wasn't such a good idea and there's been another amendment since?

There was a similar relaxation of the requirements over time regarding the placement of socket outlets on different phases or poles. Back in the 14th edition there was a requirement that all socket outlets in the same room must be on the same phase or pole, except in non-domestic premises where not practical, but even then with the stipulation that sockets on one phase/pole must be grouped together and not scattered around the room, and in no case could two sockets on different phases/poles be closer than 6 ft. apart. The 13th edition was similar but with a further restriction that the exception could be applied only to rooms over 500 sq. ft. I believe all of these restrictions have now gone.

Back to the specific switch example, there also used to be a requirement for a barrier between switches on different phases; they were commonly seen in banks of light switches for factory or retail shop lighting where the rows of lights were on separate switches and all three phases were present in the same switch box. I believe that was gone by the 16th edition, possibly the 15th.

 

[bernardgreen]

One thing to check is the rated maximum voltage of a two gang switch when the switches are each connected to different phases. 415 volts may exceed the break down voltage between the terminals of one switch and the terminals of the other switch.

 

[333rocky333]

If its MK masterseal, which is the only Mk switch i know thats suitable for outside, it will have 2 seperate grid switch modules

 

[333rocky333]

There used to be a requirement that if two outlets on two different phases were within arms' reach of each other, they had to be labelled to warn of the presence of 415V.

Mr 17th 100%man

Are you confirming that reg is now defunct, if so what amendment

 

[PBC_1966]

Are you confirming that reg is now defunct, if so what amendment

Not sure of the the exact amendment/date, but I believe it was the same one which removed the requirement for labeling on a single enclosure containing 400V: Labels only required for anything over 230V to earth, regardless of voltage between conductors within an enclosure or between two devices within reach.