16A ovens - best solution in

Discussion in 'Electricians' Talk' started by Spark19*, Oct 14, 2021.

  1. terrymac

    terrymac Screwfix Select

  2. Spark19*

    Spark19* New Member

    Ad_g - Ok thanks! So whilst it may have seemed a bit of a wacky idea to me, looks like other electricians (well at least one!) had a similar approach.
     
  3. Jimbo

    Jimbo Screwfix Select

    The female side is on the appliance lol
     
    terrymac likes this.
  4. Spark19*

    Spark19* New Member

    So I think where I’ve got to is...if there is somewhere discrete to plop a garage style/small consumer unit out of the way, populated with 2 16A breakers that’s probable a belt and braces, you’ve done all you can sir solution! Orrrr if I simply ran the existing supply through DP isolators (say 20A rated each); through the dual outlet you have kindly provided; and to the ovens; probably aok, but not quite as adherent to the manufacturer. But still improbable would be an issue!
     
  5. Ad_g

    Ad_g New Member

  6. Spark19*

    Spark19* New Member

    Useful! Thank you.
     
  7. Bazza

    Bazza Screwfix Select

    As you seem to be so concerned with absolutely following the letter of whatever. Remember that installing an additional consumer unit, perhaps on the end of an existiong circuit, creates NEW CIRCUITS. New circuits are NOTIFIABLE to the local authority, so if you are not a CPS member (and able to carry out the notification yourself) then you will need a registered electrician to install, test, certify and notify the new CU and the circuits connected to it.

    Really, all you need is a dual appliance connection plate and wire the two ovens in. Sorted. Simples!
     
  8. Jimbo

    Jimbo Screwfix Select

    with 1.5mm CSA flex connected on the end of it?

    This goes back to my original question... what if it's not a consumer unit but simply a plastic DIN rail enclosure, such as a Wylex WBE4? Drop in 2x 2-pole 16A MCBs and jobs-a-goodun?
     
    Last edited: Oct 15, 2021
  9. sparky steve

    sparky steve Screwfix Select

    https://youtu.be/QQduU8RkjD
     
  10. Bazza

    Bazza Screwfix Select

    Not a problem. as discussed above
    Worse and worse.
    The regulations state
    421.1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall:
    (i) have their enclosure manufactured from non-combustible material, ......

    What you propose IS absolutely a "similar switchgear assembly". Also you are proposing a plastic enclosure which also does not mees the requirements.

    Give it up mate. You were already there.
     
    Jimbo likes this.
  11. Spark19*

    Spark19* New Member

    I will give it up :) but just one final comment and happy to hear why this isn’t correct. If the oven develops a fault that draws anything above its intended 16A (but lower than the 32A at the breaker) there is not the manufacturer recommended protection for the pre-connected cable (or to a lesser degree the appliance). None of us on here can say that fault is impossible to arise, as the total resistance of the appliance is a function of the ovens internal load, across all circuits, including the resistive load of the element, which is manufacturer calculated. A blown resistor on an internal circuit could theoretically cause increased current draw between 16-32A. The manufacturer asks for a 16A fused connection and however you cut it, wiring it to a 32A RCBO is not providing a 16A fused connection, nor adhering to the manufacturer installation instructions. Having said that the likelihood of a fault arising that is specifically of this type is pretty low. It is more probable as other have said, a short would arise drawing more than 32A immediately, that would flip the RCBO. It is irrelevant whether we think the particular fault is likely, as the manufacturer clearly believes a 16A fused connection is most suitable. Makes sense as gives the smallest leeway for additional current draw, above the kW rating (and therefore calculated resistance/current draw) for the oven. If we say appliance fuses aren’t an electricians responsibility; even when hard wiring an appliance into the fixed wiring is the only opportunity for the fused connection to be made correctly, it’s a bit of a cop out really. What’s being described is no different than popping an oversized fuse in a plug.
     
  12. Jimbo

    Jimbo Screwfix Select

    Personally I'm going to have the sparks fit a small CU for it with 2x B16 breakers, new circuit or not doesn't really make a difference to them as part-p registered. Next complication is that the CU can't be above the ovens but must be within 2m...
     
  13. Bazza-spark

    Bazza-spark Screwfix Select

    So much unnecessary rubbish in this thread.

    The Regulations (not mandatory) require that the manufacturers recommendations are considered, not followed blindly.

    You are turning a 10 minute simple job into a notifiable expensive work. @Bazza has told you the correct and accepted way to carry out this task, I can see the correct way and I have an industrial background not domestic.
     
    Sparkielev likes this.
  14. Bazza

    Bazza Screwfix Select

    why 2 metres? What’s that all about? another urban myth probably born from some fictional belief that isolators must be within 2 metres of the appliance?
    TOTAL GARBAGE there is NO regulation that says that there must be any isolator at all. That means that there cannot be a distance for something that does exist!!

    Sorry, you making an Everest out of a gnat bite.
     
    Sparkielev likes this.
  15. Spark19*

    Spark19* New Member

    Possibly but all I’m after is a brief explanation why you think it is ok to essentially fit a fuse to an appliance double the Amperage rating that the manufacturer recommends. Because that’s the upshot here.
     
  16. Bazza

    Bazza Screwfix Select

    Already given to you, and repeated in my post above.
     
  17. Jimbo

    Jimbo Screwfix Select

    On-Site Guide H4, "one switch may be used to control both appliances provided that neither appliance is more than 2m from the switch".
     
  18. Spark19*

    Spark19* New Member

    Ok put it another way. No-one saying it’s ok to just stick with the 32A fuse can possibly know what current the cable to these ovens is capable of handling without overload. I haven’t even said the actual model of ovens I’m installing. Given the manufacturer wants a 16a fuse BEFORE the ovens it is more than reasonable to assume the cable rating cannot handle above that. So whether an industrial engineer or a domestic electrician, it’s really that simple. The manufacturer wants a 16a fuse. Unless you’ve tested the cable attached to the ovens any other view is just guesswork.
     
  19. Bazza

    Bazza Screwfix Select

    Look at the title of the book. It is called a GUIDE. It is not a regulation.
    In that book, at each paragraph the IET prints which REGULATION applies to the GUIDE. Does the text relating to the 2 metre issue gave a regulation? NO. Therefore it’s not a requirement needed to comply with BS7671.

    I rest my case m’lud.
     
    Jimbo likes this.
  20. Jimbo

    Jimbo Screwfix Select

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