Segregation Of Band I And Band Ii

[Steve100]

I am aware that Band I (ELV) and Band II (LV) circuits should be kept segregated. My understanding of the reason behind this is firstly to reduce noise interference on data cables as well as control, alarm and fire circuits. Secondly, to ensure that no emf is induced into the Band I (ELV) cables or circuit causing a higher voltage in the ELV circuits. Thirdly, if the LV cable become damaged, because it would be segregated from the ELV circuits it would reduce the likelihood of a higher voltage appearing on the ELV circuit and reducing the likelihood of someone receiving a shock. Can someone please tell me if my assumption/understanding is correct?

However I do have another query about my second point, ordinary twin and earth cable carries the same current but in opposite directions so very little magnetic field is produced as they cancel one another out. So is the concern about induced emf’s still a great one when using T&E/Multicore cable?

 

[wozz]

I personally would have thought your third point is the overriding one.  

is the concern less so about the induced emf and more about the effect such as interference ect.

 

[zak 1990]

This makes me laugh just done a shop wi another spark we were there nearly 3 weeks trunked all round the shop above the ceiling and all round band for the lights.

A week before handover, cctv alarm engineers come in run all there cables in ours. New to the shop fitting world but the spark I was with just said its the norm these days.

 

[Sidewinder]

We did a tray system with 400/690V SWA and SY on it a few years back, The BMS boys came round and run all their 24v and analogue 4-20mA and 0-10V in mickey mouse normal pvc in our tray, that weekend we ripped it all out and cut it into 1 meter lengths and left it with a note in their panel :slap

The way it should be!

The only stuff in the "power" containment, must be "power" rated!

 

[batty]

When I wired the kennels up the alarm guy a young lad pulled his cables through with mine after. When his boss came I said about it his answer was they just put a shunt or something in the panel's I should have cut them out like you did .

 

[col]

When running alarm cable through a hole alongside T&E I was told a bit of mini trunking would be sufficient segregation to stop EMI running down the alarm cable.

Always wondered if it was true (although good protection from shock if nothing else).

Anyone know if PVC trunking is effective or invisible to Electro-Magnetic Interference?

 

[NozSpark]

What,,,,, a little bit of plastic is going to be able to sheild a cable from EMI? :slap

 

[col]

exactly, but I've never seen steel conduit used.

I know there's shielded cable but that's hardly segregation is it?

 

[steptoe]

done some work on a multinational a couple of years back,

100's of metres of basket and was back a few weeks later and alarm guys had their cables in our basket,

raised it with the in-house guy who told us to get it out of 'our' tray, the alarm guys werent under his warrant so the tray was 'his' and he hadnt authorised them to use it.

my, what fun we had, we just tipped it all over the floor and then the FLT guys drove over it.!  :slap

 

[binky]

made an alarm company shift all their cables on a domestic re-wire I did years ago. Lazy sod had used all my holes in the joists, where they though i wouldn't see, despite pointing out it was not acceptable. "What's wrong with that" said the boss man, " my name on the ticket" was the reply. They moved them.

 

[Nicky Tesla]

Cable such as firetuff and micc is shielded in design, and because of this, even when run together with normal power cable, it is considered to still be segregated. 

 

[Manator]

I have to work to these spacings

Power Cable     Minimum Separation     
Voltage/Volts     between Power and Signal Cable     
115                        250mm     
230                        450mm     
400                        580mm     
3300                      1100mm     
6600                      1250mm     
11000                    1400mm     
Power Cable     Minimum Separation between     
Current/Amps     Power and Signal Cable     
5                             240mm     
15                           350mm     
50                           500mm     
100                         600mm     
300                         850mm     
600                         1050mm     
 

 

[col]

Thanks for that reminder Manator, distance is best. 

 

[Nicky Tesla]

iv never seen that separation data before manator ta,  but you dont get 450mm separation in 2 or 3 compartment trunking.  That just has a strip of plastic to seperate them just like normal yt2 trunking