ELV and mains on same cable

[ScottishGasMan]

I know your not supposed to wire controls etc with mains voltage and extra low voltage in the same cable, ie a 240v LNE and 2 ELV 24v DC data wires in a single 5 core flex.

Can anyone point me to where it says that in regs please?

 

[Robin0577]

Actually it doesn't say that as such. Band I and band II circuits can coexist in a cable of suitable design if all cores are insulated for the highest voltage present.

https://www.voltimum.co.uk/articles/installation-band-i-and-band-ii-circuits

Also, "hybrid" cables are available with additional sheathing in between band I and band II sections, e.g. http://shop.sommercable.com/en/Cabl...ridkabel-SC-Monocat-Power-212-500-0191-2.html

 

[bernardgreen]

Robin is correct, I was typing the same.

That said putting "data" and mains in the dam cable may result in corruption of the data. It depends on how the "data" is carried along the cable as to how much corruption is likely.

Hence without knowing the type and format of the data a definate answer cannot be given.

 

[ban-all-sheds]

Actually it doesn't say that as such. Band I and band II circuits can coexist in a cable of suitable design if all cores are insulated for the highest voltage present.

Which of course they would be in 5-core flex.

 

[ScottishGasMan]

I see. Thats interesting, I was under the impression you wernt allowed to run mains and ELV in the same cable regardless of data/losses, just purely as a safety issue or for possibility of induced voltages in the ELV side of the circuit.

 

[ban-all-sheds]

No - it's purely insulation strength.

 

[bernardgreen]

just purely as a safety issue

There is a afety concern. If the cable is mechanically damaged and mains voltage comes into contact with the data conductors then the data equipment at the ends of the cable may become hazardous to work on due to circuits in that equipment that are normally ELV becoming Live from the damaged cable.

If the overall system requires LV ( mains ) and ELV are carried in the same cable then the data interfaces in the equipment at each end of the cable should ( must ? ) be able to prevent LV getting past them and into the ELV area of the equipment.