segregation of circuits

[mcm]

Looking for some advice about segregation of circuits.

When filling out a domestic installation certificate would you tick the box stating electrical separation for one item of current-using equipment if a low voltage fan was installed and that was the only low voltage equipment installed.

Would this mean a tick would also need to be put in the box stating segregation of band 1 and 2 circuits.

Thanks

 

[Steve D]

Yes if it is electrically separated equipment.

Careful though, just because it's separated, doesn't necesarrily mean it is extra low voltage. Only tick segregation of band 1 & 2 if it is SELV - otherwise mark it as N/A

 

[electricians]

I would say yes to the tick in segregation....... but I'm not sure it would come under electrical seperation which normally applies to a shaver socket .

 

[mcm]

the fan is off the lighting circuit but only low voltage equipment installed. so would you still tick the box electrical separation for one item of current-using equipment.

would you tick the box segregation of band 1 and 2 circuits as wellbecause its a 12volt fan.

 

[Graeme Harrold]

I was lead to believe seperation for sure, however segregation was more to do with longer runs of cabling especially in trunking wher you have mixed voltages e.g. a 230v ring, data cabling, phone cabling etc. A shaver outlet does not tend to be wired seperately as the outlet is usually fixed to the backend of the transformer.

 

[electricians]

You would not tick the box electrical seperation as it does not apply to a low voltage fan . It is a common misconseption , most devices that use electrical seperation would be used in a swimming pool or other commercial environments - that why it reffers to one item in a domestic report

You would tick the box for seperation of band 1 and band 2 if you have seperated the elv and the lv cables .

 

[Guest123]

Chances are you will have wired from the transformer to the fan in normal T&E cable therefore you will have achieved 'segregation of band 1 & band 2 circuits' as the insulation used is rated to the highest voltage present. Tick.

As for electrical seperation, as the fan is supplied via a double wound SELV transformer than you will also have achived this. Tick.

 

[electricians]

I'm not sure that is correct Lenny , for electrical seperation the output must still be in the LV range and not elv as with a fan .

 

[Guest123]

SELV = Seperated Extra Low Voltage.

The same, but different as technically it isnt 'electrical seperation' but it is seperated from the live & earth of the supply circuit via the transformer.

 

[electricians]

Safety from shock can sometimes be ensured by separating a system completely from others so that there is no complete circuit through which shock current could flow. It follows that the circuit must be small to ensure that earth impedance's are very high and do not offer a path for shock current The source of supply for such a circuit could be a battery or a generating set, but is far more likely to be an isolating transformer with a secondary winding providing no more than 500 V. Such a transformer must comply with BS EN 60742, having a screen between its windings and a secondary winding which has no connection to earth.
There must be no connection to earth and precautions must he taken to ensure, as far as possible, that earth faults will not occur. Such precautions would include the use of flexible cords without metallic sheaths, using double insulation, making sure that flexible cords are visible throughout their length of run, and so on. Perhaps the most common example of a separated circuit is the bathroom transformer unit feeding an electric shaver. By breaking the link to the earthed supply system using the double wound transformer, there is no path to earth for shock current


There is no potential for shock and therefore a SELV fan does not come under the banner of " electrical seperation " even if it is electricaly seperated .

 

[Guest123]

As I said....the same but different.

SELV is a method of basic & fault protection in it's own right but in my mind it is also a form of electrical seperation. I agree it doesn't fall under the banner of the 'electrical seperation' method of fault protection but, as the secondary side is isolated from the supply circuit the theory is still there albeit it at a lower volatge.

 

[electricians]

I like this one , can argue about it all day , 3 weeks ago I was at the London Build conference and had the same argument with another contractor . Tony Cable turned up , and the small cockney guru solved the conudrum , he agrees with me . I always use to tick the box , and to be honest partly agree , but it does make a difference in a industrial/commercial environment as it requires a rigourous check for compliance .

 

[Guest123]

No right or wrong here mate, I just like breaking things down and debating the theory behind it all.

A forum would be boring if evryone just agreed with everyone else all the time.

 

[electricians]

your right Lenny

 

[mcm]

if the fan was 12 volt but the transformer was in the fan would this still be under selv.
would you need to tick electrical seperation box and band 1 and 2 circuit seperation box.

thanks