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Oven & hob on 13amp fused spur

Former Community Member
Former Community Member
I’ve come across an electric oven and gas hob on a cooker circuit, the cooker switch feeds a 13a fused spur which powers both the Oven & hob, hard wired into a 32amp junction box.
the oven is rated at 13 amps but the hob 3 amps Is this acceptable as the hob is protected by a 13 amp fuse?

  • 0
    davezawadi (David Stone):

    I will now set the cat amongst the pigeons.


    You are doing an EICR, is anyone going to code any of the suggestions above?

    Let's see...


    FI ... ?


    I can't say I disagree that the current situation can make it very hard for those carrying out EICRs.


    For example, I know there are installs of commercial laundry machines, where additional earthing (due to high protective conductor current) is required, and not provided. That's a potential breach of Electricity at Work Regulations (earthing not adequate) if there's a problem with the primary cpc. Yet, how would an electrical inspector know? Or the Duty Holder for that matter?


    But, how is that any different to portable appliance testing that fails equipment just because the person employed to do the inspection and testing isn't aware of the design of a particular appliance - I've seen that lots too. Or the company who decided to change all the fuses in the BS 1363 plugs on monitors in the office I was working in from 13 A to 3 A based on power on the rating plate - within a week, most of the 3 A fuses had blown due to inrush !



    However, the current situation is, that if a product comes without a pre-fitted "standard plug", you can't make assumptions about whether it's OK to use a particular protective device, as with this gas hob - if it came without a plug, and the manufacturer's instructions state a particular rating of protective device, that's what it is, which for UK market might be a 3 A fuse ... or it might easily also be a 1 A fuse in the FCU !


    Not a good situation, but an issue for product standards ... and many of them say something similar in this regard.


  • 0
    davezawadi (David Stone):

    I will now set the cat amongst the pigeons.


    You are doing an EICR, is anyone going to code any of the suggestions above?

    Let's see...


    This sounds like a C&G exam. ?


    At the beginning, I would ask the householder if there were any concerns. Next I would have a look and smell - I assume that I shall find nothing.


    Then I would have a look behind the plate of the cooker switch - not possible to do a sample! On the above information, I wouldn't expect to find anything amiss. Then I'd have a look behind the plate of the FCU. IR testing might be limited if there is a neon. I'd check Zs at the FCU. And that's about it. I would not remove the cooking appliances.


    So my only concern might be over-filled load terminals on the FCU. That's when it gets interesting! I wouldn't be entirely happy with say only two threads engaged, but if the cable passes the tug test, so be it. If the cable turned out to be loose then we have a problem. Do I attempt to put it back? I think that I would want to speak to the householder at this stage. If (a 4 mm²) cable cannot be secured, then I think C2. If it can be, then no code. (Which I think is the point that Dave was making.


    Was I over-thinking the question? ?


  • 0
    Very good Chris (as usual!). What I really meant were the other suggestions for what should be done above. 4mm cable? HR cable? 3A vis FSU or plug/socket. 2.2kW appliance but 4mm cable? As an aside would anything change if this were an induction hob, not an oven? Anything wrong with a 1.5mm cable?


    Yes Graham, I agree, and we would probably see a range of EICR results just from the suggestions above, which is not a satisfactory outcome!
  • 0
    gkenyon:

    . . .

    But, how is that any different to portable appliance testing that fails equipment just because the person employed to do the inspection and testing isn't aware of the design of a particular appliance - I've seen that lots too. Or the company who decided to change all the fuses in the BS 1363 plugs on monitors in the office I was working in from 13 A to 3 A based on power on the rating plate - within a week, most of the 3 A fuses had blown due to inrush !

    . . .

     



    Forgive me if this seems like a slight deviation but there lies a tale or two. It seems to be a question of official standards, widely available "helpful information" and the practical situation - there is lack of meeting of minds among these.


    "Helpful information" often accompanies things likes assorted packs of BS 1362 cartridge fuses. Information like "3 A fuse suitable for appliances up to 720 W", based on a simple calculation assuming mains supply at 240 V. No account taken of initial inrush of current or power factor - and of course mains is at 230 V nowadays. In the case cited above, it sounds as though someone made the decision based on this rather tenuous advice rather than on experience.


    In the dimming and distancing days of tungsten filament lamps, I used to fit 5 A fuses to portable lamps run off 13 A sockets. 3 A fuses would often blow when the lamp failed; 5 A fuses usually did not. Where the manufacturer of an appliance recommends a fuse size, I follow that recommendation and do not pretend to "improve" things by fitting a lower rating.


    I have often wondered why 3 A, rather than 5 A, seems to be the official standard for the lower fuse rating. It is not compatible with fuse ratings on a consumer unit, where you will not find a rating less than 5 A. So an appliance running off an unfused plug would be protected at not less than 5 A. Despite being "non standard", 5 A fuses are readily available in most popular retail outlets, and sometimes even recommended by appliance manufacturers. (Does anyone have any ideas on this?)


    As for computer monitors, they usually receive their mains supply from kettle-type connectors. I have found that the fuses factory-fitted in the 13 A plugs of these are often rated at 10 A, another non-standard size and not so easily available. I presume the reason for this  is to "officially protect" the IEC C14 plug, which is rated at 10 A. However I would not be overly worried if a 13 A fuse were fitted. The fuse is to protect the lead and the connector at the other end, but not the monitor, which should have is own internal fusing.


  • 0
    It is not compatible with fuse ratings on a consumer unit, where you will not find a rating less than 5 A.

    Only in the UK is the minimum normally 6A for MCBs - elsewhere lower ratings are common - e.g. the French normally supply their control circuits and low power equipment (e.g. bathroom fans) from a C2 MCB. But then they don't have the option of a 3A BS 1363 fuse in a FCU, so it's all a bit circular.

     
    I presume the reason for this is to "officially protect" the IEC C14 plug, which is rated at 10 A. However I would not be overly worried if a 13 A fuse were fitted. The fuse is to protect the lead and the connector at the other end, but not the monitor, which should have is own internal fusing.

    Indeed and a 13A fuse will likely easily protect the flex and connector from faults - but what of overloads? With Y splitters readily available you can't reply on the resumption that it'll supply at most one appliance rated ≤10A.


    Odd rated BS 1363 fuses are even known in other BS - from memory the BS for electrical distribution systems in office partions and furniture used to demand 7A fuses!


       - Andy.
  • 0
    Table 2 of BS 1363-1, which is actually referred to in the Plugs and Sockets (Safety) Regulations, now lists 3 A, 5 A, 7 A, 10 A and 13 A
  • 0
    gkenyon:

    Table 2 of BS 1363-1, which is actually referred to in the Plugs and Sockets (Safety) Regulations, now lists 3 A, 5 A, 7 A, 10 A and 13 A


    Thanks for this information, Mr Kenyon. I'm glad that British Standards now represents common practice.


    I understand that in the early days of BS 1363 plugs, the official range of fuses available was 3 A, 7 A and 13 A, but this has been revised a few times.


  • 0
    And off the beaten track, some makers seem to manufacture non-approved values as well.
    Fake fuses -20A rating for 13a plugs.

     

    A cautionary note  for those who are not so  aware that when you buy from abroad from Ebay and the like, you have all the legal liabilities as the importer, as you are the person first receiving the goods into the UK.

    M.

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