2 voltage bands, 1 double pole switch. Yes or No?

[Crosswire]

230v one side, 24v other side .

Yes or no?

Please quote reg

 

[GLENNSPARK]

528.1 brb

 

[Crosswire]

But if the 12v is run in normal twin and earth (i.e. insulated to 230v) then it is acceptable. Yes?

 

[Engineer54]

But if the 12v is run in normal twin and earth (i.e. insulated to 230v) then it is acceptable. Yes?

NO!!.....


There is no way that a DP switch can have 2 different voltages on it from 2 different systems. That's just asking for trouble, pure lunacy!!!

 

[camerabloke]

do it through a relay, safer

 

[keniff]

I don't get what you would be doing to have this situation can someone give me a example?

 

[Crosswire]

Its for a bathroom light which brings on a fan as well . Not my design, comes from the architect/electrical engineer, who have insisted on a low voltage fan.

I know it is strange but have been told to do it

 

[Crosswire]

NO!!.....


There is no way that a DP switch can have 2 different voltages on it from 2 different systems. That's just asking for trouble, pure lunacy!!!

I take your point, but how can this be supported by the regs?

 

[Engineer54]

No electrical engineer is going to design a system where a single DP switch is going to be used to control 2 systems on different voltage bands... Talk to the guy face to face and not via an arty farty Architect, who is mainly only interested in what it looks like!! I'd want a signed written and dated instruction before i would touch it!!

It's YOU that will be signing your work off, and i can assure you, this set-up does not conform in any way shape or form to BS7671, on segregation of extra low voltage bands, switching, or anything else come to that!!

 

[spark 68]

Hi crosswire,

Its for a bathroom light which brings on a fan as well . Not my design, comes from the architect/electrical engineer, who have insisted on a low voltage fan.

Presumably your Extra Low Voltage fan is supplied from a SELV source ?
In which case can you not supply the ELV primary source (the 230V AC incoming supply) from the DP switch, as this will then sort all of your problems wrt mixed supplies ?

Just a thought

Edit, or better still from a DP SW FCU suitably fused down (@ 3A)

 

[Engineer54]

A question, .... Where are the neutral/return conductors for these 2 systems?? Have they been brought to this switch back box too??

This switch would need so many different warning stickers on it, this Architect will probably end up having a heart attack. lol!!!

 

[spark 68]

This switch would need so many different warning stickers on it, this Architect will probably end up having a heart attack. lol!!!

My thoughts exactly E54! lol

Crosswire the regs are 528.X (read this section carefully)

 

[Crosswire]

Hi crosswire,



Presumably your Extra Low Voltage fan is supplied from a SELV source ?
In which case can you not supply the ELV primary source (the 230V AC incoming supply) from the DP switch, as this will then sort all of your problems wrt mixed supplies ?

Just a thought

Edit, or better still from a DP SW FCU suitably fused down (@ 3A)

This is how I would do it , as it is a much more sensible way to go about things. However I am merely a lowly installation electrician and have no input into the design process.

I just wanted to find a Reg that would support me if I chose to argue the point. However reading 528.1 I see that it does NOT forbid such an arrangement:

"EXCEPT where one of the following methods is adopted, neither a voltage Band 1 or a voltage band 2 circuit shall be contained in the same wiring system.......

i) Every cable or conductor is insulated for the highest voltage present"


Which it would be.......so it seems it is ok after all.

 

[Crosswire]

A question, .... Where are the neutral/return conductors for these 2 systems?? Have they been brought to this switch back box too??

This switch would need so many different warning stickers on it, this Architect will probably end up having a heart attack. lol!!!

The neutral of the 230v system is joined in the back box.

The 12v cable is just a switch line, so no neutral present.

Furthermore, after reading 514.10 there no requirement for warning notices, unless the voltage EXCEEDS 230v, which it doesn't.
So it seems I have no Reg to back me up, should I choose to dispute this arrangement.

 

[trev]

What the guy is proposing here is total insanity. What is wrong with the tried and trusted method which has worked perfectly well for years?