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Band I / Band II cct separation

Farmboy
Does the principal of Band I / Band II  cct separation re 528.1 apply within equipment? A DETA mechanical chime with internal transformer has LV and ELV wiring right near each other within the same enclosure (the lid of which is easily removable without tools), which seems to moot the requirement to have them separated as per the reg?


F
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    The great advantage of using a bell transformer is that an illuminated bell push can be used at the front door. Also, if you use a conventional bell it will ring for as long as the bell push is depressed, unlike some wireless chimes that only ring/chime/play for a few seconds. This is ideal for the hard of hearing or if the dogs are barking or a noisy vacuum cleaner is being used in the house. The old Friedland bell transformers were very good and lasted for years. They could be situated by a fuse box or hidden elsewhere. A mains rated cable was run to them and a bell wire run to the bell and bell push. As they were normally fixed onto a wall they never obverheated. The supply terminals and extra low Voltage terminals were situated at opposite ends of the transformer so were kept respectably separated. The tappings were 3, 5 and 8 Volts at 1 Amp., I believe so various types of bells/chimes could be supplied


    Z.
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    So how do you approach installing Equipment such as this?


    Andy Betteridge
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    Sparkingchip:

    So how do you approach installing Equipment such as this?


    Andy Betteridge 




    Made for the environment and tested for it ... simples.


    Looks like it has a shielded RJ45 jack, so in certain environments, industrial screened data cable can be used ...

  • 0
    Screened as opposed to armoured or is the a combination of both?


    I have installed standard Cat cable and armoured Cat cable, but presume neither are suitable for use within a consumer unit. 


    Andy Betteridge
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    Sparkingchip:

    Screened as opposed to armoured or is the a combination of both?


    I have installed standard Cat cable and armoured Cat cable, but presume neither are suitable for use within a consumer unit. 


    Andy Betteridge 




    If the cable is not rated for the highest voltage present, then you could create a new "wiring system" for the cable within the panel, i.e. its own containment, perhaps flexible conduit, but more usually in a control panel, say, dedicated [slotted] trunking, to help achieve the separation for safety. This is what usually happens in control panels to EN 60204-1 and/or EN 61439-series.


    It's really no big deal, provided the safety and EMC requirements are met. Even with the EMC, there are conditions for zero separation in BS EN 50174-series, which can be applied more easily to CATx cables used for Ethernet networks.

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    tattyinengland:

    Well consider a motor control centre where voltages of any size may be present. The controls from automation equipment and telemetry are likely to be present and cables carry no volts at all are common monitoring whether a contactor is open or closed for example. 

     



    An MCC would probably be an industrial or commercial application. BS 7671 wouldn't apply in that case, i.e. above 100 Amps.


    Jaymack
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    Your copy of BS7671 is clearly a bit different to mine.  I'd like commercial 690V and 400V 3 phase supplies with a few hundred amp loads to be designed to BS7671 if it is practical please, and some high power stuff too if we have to.


    The 11KV (6k6 to ground) side of the transformer comes under different rules to be fair, but fixed installation at 1000V RMS and down at any current you fancy could be  BS7671.

    Are  you perhaps thinking of the on-site guide ?

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    Jaymack:




    tattyinengland:

    Well consider a motor control centre where voltages of any size may be present. The controls from automation equipment and telemetry are likely to be present and cables carry no volts at all are common monitoring whether a contactor is open or closed for example. 

     



    An MCC would probably be an industrial or commercial application. BS 7671 wouldn't apply in that case, i.e. above 100 Amps.


    Jaymack 

     




    I'm not sure about the rationale of 100 A being a cutoff for BS 7671 - it's definitely only on voltage range; however, BS 7671 does not apply to pre-manufactured assemblies which are to comply with appropriate standards.


    If the component were pre-manufactured into the unit, the selection and fitting of the component, and any wiring connected during manufacture of the panel, would, I agree, be covered under BS EN 60204-1 and/or BS EN 61439-series as appropriate. Selection and installation of the panel, if within the voltage range of BS 7671, is within the scope of BS 7671.


    BUT, installations of cables brought in from outside the enclosure on-site are covered by BS 7671 if they are LV or ELV, so it's likely an external comms cable, as with the other connecting cables of the assembly, would be within the scope of BS 7671.


    I've worked on many MCCs that are installed wholly (both input and output are LV, and controls/comms are ELV) or partly (input and/or output HV, but LV and ELV components and controls are connected) within the scope of BS 7671.

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