short circuit capacity (kA) BS3036 semi enclosed fuse

Discussion in 'Electricians' Talk' started by steve CF, Sep 5, 2005.

  1. steve CF

    steve CF New Member

    periodic inspection report asks for short circuit capacity of protective device

    i have BS3036 semi enclosed fuses

    on site guide states S1A 1kA SA2 2kA SA3 4kA

    anyone know which value to enter for a standard BS3036 fuse
  2. unphased

    unphased Screwfix Select

    Steve

    Unless the fuse holder clearly identifies which rating it is designed for then you have no choice but to assume worst case and put 1kA. If your PFC exceeds 1kA then clearly there is a case for changing to mcb's or cartridges which have much greater short circuit capacities.

    UP
  3. sparky Si-Fi

    sparky Si-Fi Well-Known Member

    Go with what UP says Steve

    99% of the time I enter 1KA for short.c.capacity's for re-wireables.

    si
  4. unphased

    unphased Screwfix Select

    Ullo sifi m8

    Can you help with my lampost post puzzle? Not got much confidence in what I am doing for the choices of wiring, lamps, lampholders etc. Any advice would be welcome :)

    UP
  5. steve CF

    steve CF New Member

  6. sparky Si-Fi

    sparky Si-Fi Well-Known Member

    How about short circuit ratings for BS 1361 Cartridge fuses in a Domestic Install.

    Dont see that many round our neck of the woods,but saying that out here in the sticks we just plug the Sky box in the gas light (not forgetting to use the correct adaptor)

    Will get back to you on your Light Roy

    Si is UP:)) ) early tomorrow ready to start one out of three re-wires................spin the bottle?
  7. unphased

    unphased Screwfix Select

    Regarding BS1361 fuses...I have been doing some subbie work recently for NICEIC enrolled Contractor and, like the other sparks I was working with, was leaving the box blank :)() cuz I didn't know either. As it happened they had an informal inspection of their test certificates recently and they suggested putting 16kA in the absence of better info. So now I just put 16kA in the box.

    Cheers for that sifi...good luck with the rewires. I am doing a barn supply this week, lampost (hopefully) sometime next week, then back to the subbie work ;)

    UP
  8. sparky Si-Fi

    sparky Si-Fi Well-Known Member

    Hullo Roy

    Just had a squizz at OSG page 50 in the Blue book (brown is buried in the depths of an Addis stack-on box in the van)

    Ok Cartridge fuse to BS 1361 type 1 Rated short circuit capacity 16.5 KA

    Cartrdige fuse to BS 1361 type 2 a staggering 33KA rated short ciruit capacity.

    if you manage to take the last one out,probably playing your harp at the same time
  9. unphased

    unphased Screwfix Select

    33kA is heap big ampage for a type 2! Thats what I will use now for the 'IIb' ones that I come across most often and 16.5kA for the unknown...plenty of those about. 16kA is max PFC likely to be encountered in domestics anyway :).

    Have you seen those RO80 General Electric fuses? What would they be ? 80A? type 1?

    UP
  10. Elec Nerd

    Elec Nerd New Member

    The reason the utility companies use BS 1361 fuses is to protect their network.They sometimes use BS88 which are 80kA for ac and 40kA FOR dc.This is more for commercial/industrial.
    Notice the figure you get by enquiry for a pme system is 0.35 ohms and 16 kA.Thats why the 1361 hrc fuse is used.
    The good thing about having these fuses is that you can use them as secondary protection for short circuit protection.So if you measure 11kA at your DB,you don`t need to change your mcbs that may be rated at 6 0r 10 kA.
  11. autonull

    autonull New Member

    Steve

    Unless the fuse holder clearly identifies which
    rating it is designed for then you have no choice but
    to assume worst case and put 1kA. If your PFC
    exceeds 1kA then clearly there is a case for changing
    to mcb's or cartridges which have much greater short
    circuit capacities.

    UP

    I dont think you need to change the BS3036 fuses up to mcb's if your supply is protected at the source by a bs1361 fuse, leccy board fuses.or bs88's.
  12. unphased

    unphased Screwfix Select

    Hi autonull

    You do need to if the PFC exceeds the rated value of the short circuit capacity of the protective device. Thats the purpose of doing the test or calculating it from Ze.

    Adirct short across the phase and netral at the fuse incomer would cause it to explode if not up to the task.

    UP
  13. Elec Nerd

    Elec Nerd New Member

    Unphased.
    He doesn`t need to change his fuses,because the bs 1361 give him secondary protection against short circuit.I think it is gn6.They will see the fault and react quicker.
    Also he does a Ze to determine if he has an external earth.He then re connects his incoming earth to get his Zs as now you want all parallel paths FOR A max pfc
    Not much difference in a domestic,but on a steel portal frame zs can be far less than ze.
    On larger installations the utility companies use bs88 because they can handle up to 80 kA.
    Hope this helps
  14. autonull

    autonull New Member

    Hi autonull

    You do need to if the PFC exceeds the rated value of
    the short circuit capacity of the protective device.
    Thats the purpose of doing the test or calculating it
    from Ze.

    Adirct short across the phase and netral at the fuse
    incomer would cause it to explode if not up to the
    task.

    UP


    Hi UP,

    Guidance note 3, 2.7.15 states

    Where a service cut out containing a cartridge fuse to BS1361 type 2 supplies a consumer unit which complies with BS5486-13 or BS EN 60439-3, then the short circuit capacity of the overcurrent protective devices within consumer units may be taken to be 16kA.

    In other words the service cut out fuse protects the integrity of the board and fuses and these need not be changed to comply with short circuit current breaking requirements.

    auto.
  15. NIC QS

    NIC QS New Member

    yer but chances are it wont meet max zs values for what ever circuits there supplying anyway eg,{30A BS3036 max efli for .4 disconection time is 0.91ohms}i come across higher values than that on a regular basis but there biggest downfull is overload, they will take twice there rated current before they operate eg a 30A will take nearly 60A before it operates so if you have an overloaded ringmain say with 45A on it,with a bs3036 protective device it will stay there all day and not operate! now tell me thats not a fire risk...i hate the things my advice would be to change them!!!
  16. Elec Nerd

    Elec Nerd New Member

    The original question was short circuit protection not overload.
    A BS3036 is fine for overcurrent protection if the correct correction factors are applied.They are only a fire risk if coordination is not in place.That is why curves for 3036 fuses are still published in BS7671.Every protective device is a fire risk if the max Zs is exceeded on the circuit.
    iF you have 45A on a ring circuit look at the curves in appendix 3 and you will also see that a BS1361,BS88,BS60898,BS3871,AND 61009 will all take the 45A all day without rupturing.
    If you carry out a pir and come across rewireable fuses what regulation is breached?Ask your local engineer.
    Just because you don`t` like them, that is not a reason to give your customer to change them.Find the reg No then post it
  17. unphased

    unphased Screwfix Select

    Hi elec nerd and autonull

    Appreciate your explanations. I have learned something. One of the reasons I love this forum. Thanks guys.

    Regards

    UP
  18. NIC QS

    NIC QS New Member

    alright then ill give you another example came across 60A rewirable fuse carrier in a factory with 2 bits of 2.5mm cable in it instead of fusewire and the reason for this is they dont make 60A fusewire anymore so tell me thats not a fire risk! or a good enough reason to change them? and ill give you another good reason to recommend changing then to your customers, who wants to be looking for fuse wire at 10oclock at night in the dark after one has blown? and how many lives have BS3036 fuses saved when someones being electricuted?i stand by my original comment i dont like them and would recommend any body whos got them to upgrade to a more modern protective device...
  19. Elec Nerd

    Elec Nerd New Member

    NIC QS,Why do BS 3036 fuses in your area electricute people?Tell them to stop now,or they will have a revisit!
  20. NIC QS

    NIC QS New Member

    the point i was trying to make was that a split load consumer unit with an rcd and mcbs has got to be better than one with just rewirable fuses any day for any number of reasons!and nobody likes a smart ****!!!

Share This Page