Multi voltages in the same containment.

[GBDamo]

​

Requirements of Regulation 528.1​

Unless the segregation requirements of Regulation 528.1 are satisfied, circuits of voltage Band I and voltage B and II should not be contained in the same wiring system as a circuit exceeding low voltage, and a Band I circuit should not be contained in the same wiring system as a Band II circuit.

To minimise the risk of interference between cables of differing voltage levels, every cable or conductor should be insulated for the highest voltage present. Where a multicore cable contains Band I and Band II circuits, as shown in Fig 1, all conductors should be insulated for the highest voltage carried by the cable. One example of this requirement might be where certain cores of a multicore armoured cable to BS 5467 supply SELV equipment, such as a cooling unit having an external condenser requiring a low voltage supply (Band II) and a control circuit (Band I).

Not wanting to derail the Dodgy work pictures thread but a comment was made that a fire alarm FP200 shouldn't be in trunking with 230V band 2 cables.

Above is a quote from an NICEIC article discussing this subject.

I've read that as the cable is "banded" not its voltage going through it.

So if FP200 is being used for a fire alarm it's fine in the same compartment as 230V band 2 cables as FP200 is a band 2 cable even though it only has 24v going through it.

The example of multi voltages in a multicore cable suggests its the insulation level of the cable that is important not the voltage going through it.

 

[telectrix]

yep. as long as all cables are rated to or above the highest voltage present.

 

[timhoward]

Yep, that was my fault, and my mistake. Apologies.

 

[timhoward]

Out of interest, does anyone have an up-to-date copy of BS5839?
I won't quote my old version but this topic is (or was) mentioned in section 26.
I think is where my pre-conceived idea came from.

 

[GBDamo]

Yep, that was my fault, and my mistake. Apologies.

Didn't want to make it a dig at you personally as it had me questioning my own understanding.

Just looking for confirmation.

 

[timhoward]

Didn't want to make it a dig at you personally as it had me questioning my own understanding.

Just looking for confirmation.

No worries at all! I appreciated the way you handled it.
I worked in the fire alarm sector a good while ago once and was told simply not to do this, so I never did. I'd always assumed that reg in BS7671 was the reason. Plainly not!

I suspect but can't prove that BS 5839 part 1 still says you "should not" do this. My 2008 copy certainly tells you not to.
(It also says isolation should be double pole and lockable in both states.)

I'd be interested to know what the current version says. For me this is another reason why it's best leaving it to the alarm-installers to take the blame -if their willing to sign a commissioning certificate then their problem!

 

[Ray Pooley]

​

​

Not wanting to derail the Dodgy work pictures thread but a comment was made that a fire alarm FP200 shouldn't be in trunking with 230V band 2 cables.

Above is a quote from an NICEIC article discussing this subject.

I've read that as the cable is "banded" not its voltage going through it.

So if FP200 is being used for a fire alarm it's fine in the same compartment as 230V band 2 cables as FP200 is a band 2 cable even though it only has 24v going through it.

The example of multi voltages in a multicore cable suggests its the insulation level of the cable that is important not the voltage going through it.

I think that might have something to do with the fact that you don't want the fire alarm being disabled by a fire that might break out in the general electrical trunking. It would make sense to me if the fire alarm circuit had its own path to the consumer unit.

 

[GBDamo]

I think that might have something to do with the fact that you don't want the fire alarm being disabled by a fire that might break out in the general electrical trunking. It would make sense to me if the fire alarm circuit had its own path to the consumer unit.

Would make sense in a belt and braces kinda way, but isn't that why we use FP.

If you're still in the building after 2hrs the alarm supply failing is probably the least of your problem.

 

[westward10]

It makes no sense.

 

[Dartlec]

Out of interest, does anyone have an up-to-date copy of BS5839?
I won't quote my old version but this topic is (or was) mentioned in section 26.
I think is where my pre-conceived idea came from.

I have what I think are the up to date versions (5839-1:2017, 5839-6:2019+A1:2020)

Section 26 in 5839-1 refers to "cabling, wiring and other interconnections", mostly talking about fire resistance, but also has this section:

It is the responsibility of the designer to ensure that the electrical characteristics of the cables, including​

current carrying capacity and voltage drop, are suitable for the system. The choice of cable and routes​

selected need to take into account the need to avoid electromagnetic interference from other cables​

and sources of electromagnetic radiation, particularly in the case of systems in which cables are used​

for transmission of data (such as addressable device circuits). In the latter case, the cable selected also​

needs to be compatible with the characteristics of the data transmission e.g. speed and waveform, and​

remain so for an adequate length of time during the relevant exposure to fire for the category of cable.​

The circuits of fire alarm systems need to be segregated from the cables of other circuits to minimize any​

potential for other circuits to cause malfunction of the fire alarm system arising from:​

• breakdown of cable insulation of other circuits and/or fire alarm circuits;​

• a fire caused by a fault on another circuit;​

• electromagnetic interference to any fire alarm circuit as a result of the proximity of​

another circuit; or​

• damage resulting from the need for other circuits to be installed in, or removed from, ducts or​

trunking containing a fire alarm circuit.​

If that adds any clarity?

 

[Lister1987]

I have what I think are the up to date versions (5839-1:2017, 5839-6:2019+A1:2020)

Section 26 in 5839-1 refers to "cabling, wiring and other interconnections", mostly talking about fire resistance, but also has this section:

It is the responsibility of the designer to ensure that the electrical characteristics of the cables, including​

current carrying capacity and voltage drop, are suitable for the system. The choice of cable and routes​

selected need to take into account the need to avoid electromagnetic interference from other cables​

and sources of electromagnetic radiation, particularly in the case of systems in which cables are used​

for transmission of data (such as addressable device circuits). In the latter case, the cable selected also​

needs to be compatible with the characteristics of the data transmission e.g. speed and waveform, and​

remain so for an adequate length of time during the relevant exposure to fire for the category of cable.​

The circuits of fire alarm systems need to be segregated from the cables of other circuits to minimize any​

potential for other circuits to cause malfunction of the fire alarm system arising from:​

• breakdown of cable insulation of other circuits and/or fire alarm circuits;​

• a fire caused by a fault on another circuit;​

• electromagnetic interference to any fire alarm circuit as a result of the proximity of​

another circuit; or​

• damage resulting from the need for other circuits to be installed in, or removed from, ducts or​

trunking containing a fire alarm circuit.​

If that adds any clarity?

Dump of 26 to aid discussions