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BS 8436 Cable

Jonesy
Hi all I am new to the Forum.


I have a question regarding BS 8436 Compliant Cables. I am aware iof the requirement to protect circuits wired in BS 8436 Cables with "B" Type devices etc due to the requirement to limit fault current in the event of the cable being penetrated by a nail or a screw. However, what if you install the cable clipped direct to the surface and on Cable Tray or basket where the risk of accidental penetration is very low, would it them be acceptable to protect the circuit with "C" Type devices?


I have hunted high and low on the internet for an solution but have failed to find a definitive answer.
  • Former Community Member
    0 Former Community Member
    Hi Keith welcome to the forum, your suggestion sounds reasonable to me and here is a related topic from the previous forum platform :

    https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=61535&highlight_key=y&keyword1=Bs8436%20nail
  • 0
    I guess it boils down to why BS 8436 cable was specified? If it's because it's a bit of a rough environment and otherwise something like SWA would be used then you'd probably want ADS to operate in the case of cable damage even if it's not from nails/screws being driving unseen though a wall.


    If it's the type of environment where a simple soft-sheathed cable like T&E (or flex) would be acceptable, then ADS not working on the foil sheath isn't so much of an issue.

     

    due to the requirement to limit fault current in the event of the cable being penetrated



    Just to be clear - MCBs can't limit fault currents (that's a direct result of the source voltage and the loop impedance) - they can only limit the energy let-though (the product of the fault current and disconnection time).  As it happens, C-types rated 16A and below have the same (or lower) energy let-though as B-types rated over 16A but not over 32A (and might be lower again by manufacturer's data) - so "B-type only" might be a rather over-zealous simplification.


      - Andy.
  • 0
    Looking at a cable data sheet the answer is no.


    Protective devices used for these cables shall be either Type B to BS EN 60898 or Type B RCBO to BS EN 61009-1. The protective devices shall have a maximum let through energy (l2t) of 42000A2s when used with 1.0mm2 or 1.5mm2 cable and 60000 A2s when used with 2.5mm2 or 4.0mm2 cable.


    It is not designed for use on cable tray, why are you proposing to use it?


    Andy Betteridge
  • 0
    Thank you for your replies.


    I am looking to use it as an alternative to SWA cable base on ease of installation and coat in commercial installations.


    Andy Lewsbury - I understand the concept of  I2t/K2S2. And I agree that the restriction to limit the circuit protection to B Type only is an overkill. The cable is to be clipped direct on the walls and supported on cable tray/basket containment with a low risk of penetration.


    Sparkingchip - I am looking at the BATT Cable Data sheet for their Guardian XLPEAli tube LSZH Cable and they provode current carrying capacities for Reference 11 (on cabe tray) . I am interested to hear which manufacturers data sheet you are looking at?


    I was recently told by a contact on Linkedin that manufacturers have undertaken improvements to the cable and that the B Type requirement had now been relaxed. However, I cannot find evidence of this on any manufacturers website .
  • 0

    Sparkingchip:
    Looking at a cable data sheet the answer is no.


    Protective devices used for these cables shall be either Type B to BS EN 60898 or Type B RCBO to BS EN 61009-1. The protective devices shall have a maximum let through energy (l2t) of 42000A2s when used with 1.0mm2 or 1.5mm2 cable and 60000 A2s when used with 2.5mm2 or 4.0mm2 cable.


    It is not designed for use on cable tray, why are you proposing to use it?


    Andy Betteridge 





  • 0

    Keith Jones:

    Thank you for your replies.


    I am looking to use it as an alternative to SWA cable base on ease of installation and coat in commercial installations.


    Andy Lewsbury - I understand the concept of  I2t/K2S2. And I agree that the restriction to limit the circuit protection to B Type only is an overkill. The cable is to be clipped direct on the walls and supported on cable tray/basket containment with a low risk of penetration.


    Sparkingchip - I am looking at the BATT Cable Data sheet for their Guardian XLPEAli tube LSZH Cable and they provode current carrying capacities for Reference 11 (on cabe tray) . I am interested to hear which manufacturers data sheet you are looking at?


    I was recently told by a contact on Linkedin that manufacturers have undertaken improvements to the cable and that the B Type requirement had now been relaxed. However, I cannot find evidence of this on any manufacturers website .




    What about asking the manufacturers tech dept for their view?


    F

  • 0
    The stated application is:


    APPLICATION

    Screened cable for use in walls, partitions and building voids where there is a risk of damage or penetration from nails, screw fixings etc.


    Running on cable tray either a Type C MCB upfront suggests that it will be a industrial application such as motor supply or the like, where as the stated application suggests domestic or commercial usage for lighting and power, particularly if you consider the sizes available.


    Andy Betteridge
  • 0
    Batt give the application as:


    Applications: Power circuits, lighting, air-conditioning, call systems, data networks, signage supplies, computerised checkouts.

    http://www.batt.co.uk/products/view/306/Guardian-Ali-Tube/LSZH-Cable-BS8436-600/1000V


    http://www.batt.co.uk/upload/files/guardianali-tube-lszhcablebs8436300-500v_1571219418.pdf


  • 0
    Sparkingchip.


    Thanks for your input. Batt cables state that their cable can withstand a fault current of up to 200 amp which according to Fig 3A5 BS7671 is the current required to operate a 20 AMP Type C MCB  0.1 TO 5 Seconds. 


    All I have to do now is carry out the cable sizing calculation.
  • 0

    Keith Jones:

    . . .  Batt cables state that their cable can withstand a fault current of up to 200 amp which according to Fig 3A5 BS7671 is the current required to operate a 20 AMP Type C MCB  0.1 TO 5 Seconds. . . 




    Yes, but the actual fault current will be limited by the impedance of the supply. You may find that significantly more current flows - if it is a few thousand amps, your cable may not survive. As Andy has already said, the only thing you can limit, is the energy let through, by choosing a fast enough mcb. 


    Regards,


    Alan. 

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