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Checking oven is suitably connected without access to fuse

Discussion in 'Electrics UK' started by lt8480, 2 Aug 2016.

  1. lt8480

    lt8480

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    Whilst doing some minor kitchen DIY in a house we've just purchase I've noticed the oven is on a plug behind a cupboard.

    We don't have the manual for the oven but I believe it is an Electrolux EOC65140X (based on google image searching).

    An online manual (p55) for this oven suggests a 15amp fuse should be fitted and 2.5mm2 cable. Forgive my naivety but I thought UK plugs were 13amp maximum - so a little curious about this installation.

    Unfortunately I can't get easy access to the plug to check the fuse due to how it is fitted.

    No power rating is listed in the manual, but from my very basic calculation (using the 15amp requirement) I work out the power of the oven could be up to 3600 watts. Looking online at replacement parts - the fan element in 2400 watts and the bottom element 1000 watts, the manual suggests these can be used combined so I guess should allow for 3400 watts, which seems to correlate nicely with the 15amp requirement.

    The fan oven seems to work fine when I quickly tested the oven works, but I haven't tested the combined setting, and now hesitant to do so!...

    So, my questions are:

    1.
    If I try to use the combined setting and only a 13amp fuse is fitted I guess the electrics should trip due to overloading a 13amp fuse? (as 3400w and 230/240v would result in 14+ amps being required)

    2.
    If the power does trip, is it safe to assume a 13amp fuse is fitted?

    3.
    Or, could something else happen? (i.e. it doesn't trip and causes an overheating / fire risk?)

    4.
    If the combined function works okay, is is safe to assume a 15amp fuse is fitted?

    5.
    If it turns out to be 13amps only - would it still be safe to use either heating element separately until I get this sorted as independently they are 2400W and 1000W ? (i.e. if I'm really not sure about this can I use the oven or grill separately and safely?)

    Any help on this much appreciated!
     
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  3. ericmark

    ericmark

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    The problem is if the plug over heats for an extended time it can anneal the metal in the socket and cause it to lose grip on the pins of the plug and so create a poor connection which will then heat up and damage both plug and socket. If the socket is either in free air or better still in the forced air cooling from the oven although in theroy over loaded in practice because the element in the oven soon starts to cycle on and off it is unlikely to either blow the fuse or cause any other problems. However should you see any discolouring of the plug or socket then you need to correct the situation.

    Although rated at 13A the 13A fuse will take well over 13A for a short time.

    To correct depends on where the supply comes from, it as it should be it is a dedicated supply then a cooker connection unit can be used and the over load is the trip in the consumer unit. However if not dedicated specially if on a ring final then a new dedicated supply is required from the consumer unit. This is a lot of work in most cases.

    One cheat which may work is to use a fused connection unit (FCU) although still using a 13A fuse, because it is built into the wall it is able to dissipate the heat better so the fuse is less likely to blow and there is no plug to overheat.

    When the 13A plug was modified to include insulation on the live pins to stop you touching the pins when inserting or withdrawing the plug this also removed the brass to transmit heat away from the plug, the result is plugs today struggle to dissipate the heat generated with a 13A fuse if the load is for an extended time like a 3kW electric fire, but have no problem with a 3kW electric kettle simply because it does not take that long to boil. All fuses make heat of course that's how they work. So once up to temperature the oven switches on/off so in real terms unlikely to be a problem.

    In theory fixed items over 2kW should have a dedicated supply or at least the power used should be considered when planning the electrical installation, if these items are central on the ring final there is no problem, but if grouped to one end, then overload is possible.
     
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  4. Taylortwocities

    Taylortwocities

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    Yes, but the manual says COOKER CONNECTION POINT. NOT a fused plug!

    Basically this oven needs a separate circuit connection to the consumer unit. The cable should be minimum 2.5mm² and the fuse/MCB in the consumer unit should be between 15A and 20amp.

    If it is on a plug, then this is wrong? What circuit is the oven plugged in to? Sometimes "kitchen fitters" steal an existing cooker circuit to do all sorts of stupid things.

    EDIT As Eric says, the oven will probably work for some time with a plug and 13A fuse. The only thing that might blow is the fuse in the plug, and that will be less than convenient.
    I am assuming that the previous owners have used that oven for some years without anything catching fire, but it needs sorting, properly. This sort of lash up is doomed to fail, sooner or later.
     
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  5. lt8480

    lt8480

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    Thanks for the replies.

    So using both the fan oven and grill simultaneously on the combined function is definitely not recommended. - To be honest I've never used this function before on any oven so doubt I will start now!

    The oven looks almost new and barely used so suspect the previous owners weren't chefs or cooking aficionados!

    We intend on fully stripping the house and relocating the kitchen in the next 1-2 years to another area... so ideally we would prefer not to spend money on trying to sort this out now,as we will be completely re-wiring the house then anyway.

    What are your thoughts on using the fan oven (2400W) or grill (1000W) separately only which would presumably only require 10A and 4.2A respectively. Is this safe to do as below the 13A that is assumed or any risks on this?
     
  6. JohnW2

    JohnW2

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    I'm back - and thanks to those who expressed concern about my (hectic-life-related) absence!
    Maybe but, as you know, diversity says that one can treat a 15A cooking appliance load as being only 11.5A.
    I rather doubt that would happen. As we've discussed before, it requires a continuous current of around 22A to blow a 13A plug fuse.

    Kind Regards, John
     
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  7. EFLImpudence

    EFLImpudence

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    Welcome back - one in, one out.
     
  8. JohnW2

    JohnW2

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    Indeed - and thanks. I trust that all is well with you.

    My period of hectic life actually only lasted a small number of weeks, but I've never been in the habit of coming to the forum to look for activity - I come here only in response to e-mail notifications relating to 'watched threads'. By the time my life was back to relatively normal, all the threads I was 'watching' had dried up, so there were no more notifications, hence I never came here!

    Kind Regards, John
     
  9. Taylortwocities

    Taylortwocities

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    Yes, quiet around here now, isn't it?
     
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  11. JohnW2

    JohnW2

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    Sort-of - although some of the noise has, in recent times, moved to PMs :)

    Kind Regards, John
     
  12. Taylortwocities

    Taylortwocities

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    Yes, had a treatise to read myself.
    Anyway, back to the topic..............
    Cheers TTC
     
  13. ericmark

    ericmark

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    I have a stand alone cooker, and my wife loves the door closed grilling option. Upper grill is as normal, but grill built into oven with door closed uses the oven fan as well as the element so heat is directed under the food as well as on top. Instead of turning the food being grilled many times, with door closed grilling it is turned once.

    I think from memory there are 11 settings on the oven with combinations of rear heating, bottom heating and top heating, the rear always has fan on, with the oven there are instructions on how to use, but it seems Mrs Beaton's cook book has been altered over the years, and instructions on damper positions which would have altered the area of oven heated with old solid fuel cookers has been removed, and Gas Marks added which would not have been in the original book. As a result getting cook books to tell you how to use the cooker is hard.

    When we experimented with the different functions it was noted as one would expect, when all elements are in use the oven heats up quicker so in real terms it does not use any extra power over a half hour time period. As to if my cooker has any special device to stop overload I don't know, but total power is something like 11 kW but still recommends a 32A supply.

    Mother has a built in oven and it seems there is a time sharing system so it alternates between elements, the oven is not as good as my cooker's oven but still has 7 options. Some hot plates have options to set them for different supplies, as to if ovens have the same options I don't know. But clearly from my mothers oven adding up size of elements does not always work.

    If the plug is white I would just keep an eye on it to see if there is any discolouration and if not carry on and don't worry.
     
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  14. lt8480

    lt8480

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    Thanks ericmark, that's quite interesting.

    I suspect in our case the heating elements do work together based on the 15 amp recommendation otherwise if not then I don't think there would be any need to go so high if they cycled.

    Think we will keep an eye on it for a bit and then when we do the kitchen make sure its all redone correctly.

    It seems like a good quality oven (as over £550 new), so would be a shame to replace with something cheap just to suit the less than perfect electrics, and painful to spend money upgrading the supply when it will need redoing in a year again when we move the kitchen.

    Does anyone have any thoughts on whether using the heating elements independently would be sure to bring the oven below the 13amp rating? I suppose it won't do any harm but just want to try and minimise any risk.
     
  15. EFLImpudence

    EFLImpudence

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    Can you not find out for sure?

    There will be a sticker somewhere - usually around the door plus at the back.
     
  16. JohnW2

    JohnW2

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    Yes, provided that (as is the case) none of the individual elements are greater than 3,000W (3kW) then there would be no risk of exceeding 13A if you only used them one at a time.

    Also, don't forget that, even if you used all the elements at once, after the brief initial period of warming up, they would be 'cycling' on and off, controlled by their thermostats, so that the average current over any reasonable period of time would be less than 13A - that's the reasoning behind the concept of "diversity" which I mentioned.

    Kind Regards, John
     
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  17. lt8480

    lt8480

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    Thanks JohnW2 that's great.
     
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