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Downsizing electric oven. Smaller cable required?

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  1. #1
    gasfixeruperer
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    Default Downsizing electric oven. Smaller cable required?

    New stove I'm going to install is gas on top with electric grill and oven. Power use on the badge is 2500 watts. The existing all electric stove is fed by a huge cable. Probably 4mm. Before I get a sparkie in for a quote, I'm just wondering if he would need to replace this cable with a smaller one back to the fuse box and replace the 32amp breaker or just quote for connecting from the existing cable. It's a queensdlander so easy to see the old wire running 10m from box to stove. Many thanks

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    Community Moderator phild01's Avatar
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    I assume the new oven has a 15A plug on it. Even if it is hard wired, your existing cable easily handles it if 4mm. I think reducing the CB might be an option but I'd definitely leave existing cable alone if in good condition. Just my 2c.

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    The circuit breaker is there to protect the wiring so really there shouldn't need to be anything changed.

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    The new upright stove doesn't have a plug fitted or cable/flex. Just a terminal box ready for wiring to. Doesn't oversizing the cable and fuse create a greater risk should a fault occur ie.. short circuit. Forgive the silly question. I'm olld school UK where the plugs have fuses and are hardly ever bridged out with tin foil.

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    Quote Originally Posted by Peeeeda View Post
    The new upright stove doesn't have a plug fitted or cable/flex. Just a terminal box ready for wiring to. Doesn't oversizing the cable and fuse create a greater risk should a fault occur ie.. short circuit. Forgive the silly question. I'm olld school UK where the plugs have fuses and are hardly ever bridged out with tin foil.
    When I said reducing the CB rating as an option, this is precisely what I considered. I know the CB is rated appropriately to protect the wiring but I think it is good practice to keep it's rating closer to the protected appliance that may not have protection included. But I guess a valid argument is that is an irrelevant consideration as if it needed such protection the appliance would include it. Just an option as it doesn't have to be at the full rating of the wiring. I think your sparky will just leave all as is.

    Just wondering, I know UK plugs have fuses but how does this work for the kettle using the computer's power cable, as can happen in Aus.

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    Keep the same cable but a problem you may come across is the termination box is too small for the 4mm cable so your electrician will change the size of cable near the stove with a Jbox and use a smaller cable to the oven.

    He will also change the CB to the correct size.

  7. #7
    Community Moderator phild01's Avatar
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    Quote Originally Posted by Bros View Post
    Keep the same cable but a problem you may come across is the termination box is too small for the 4mm cable so your electrician will change the size of cable near the stove with a Jbox and use a smaller cable to the oven.

    He will also change the CB to the correct size.
    Hi Bros
    Just wondering with something I need to get done. I was running 4mm to a stove point but intended to run 2 15A power outlets. Will the same issue arise for me regarding termination difficulty?

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    Quote Originally Posted by phild01 View Post
    [1]When I said reducing the CB rating as an option, this is precisely what I considered. I know the CB is rated appropriately to protect the wiring but I think it is good practice to keep it's rating closer to the protected appliance that may not have protection included. But I guess a valid argument is that is an irrelevant consideration as if it needed such protection the appliance would include it. Just an option as it doesn't have to be at the full rating of the wiring. I think your sparky will just leave all as is.

    [2]Just wondering, I know UK plugs have fuses but how does this work for the kettle using the computer's power cable, as can happen in Aus.

    Hi
    [1]Fully agree
    If that is the only load on the circuit, best to have the OLCB match the actual load.
    The same action as one would take, if having to use very large cables compared to the load rating to reduce voltage drop
    The wiring in the stove will not be 4mmx


    [2[]Beware of old computer leads , many are not 10A rated.
    Very quicky melt the insulation if used on 10A loads!!!


    t

  9. #9
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    Definitely no problems with the higher rated cable from a purely electrical perspective. The only possible issue as others have said is with terminating it, but if it's 4mm2 then most likely even that won't be a problem.

    And +1 to the electric oven with gas cook top. A sensible choice there.

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    Quote Originally Posted by Bros View Post
    Keep the same cable but a problem you may come across is the termination box is too small for the 4mm cable so your electrician will change the size of cable near the stove with a Jbox and use a smaller cable to the oven.

    He will also change the CB to the correct size.

    Couldnt you just put spade/ring lugs on the cables to terminate? Or are you talking about there not actually being room for the cable in the entire box?

    I wired a 40A 10mm2 oven circuit today to a 900mm oven/5 burner induction cook top combo. The electrical box on the stove was tiny

  11. #11
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    I was just echoing my problems with the oven I had to do recently which required 6mm cable in the tiniest of J boxes the distance was so short it would not have been possible to put lugs on as there would have been to much strain on the lug from the bend needed in the cable.

    Why they went away from the old way beats me as you had plenty of room for terminations.

    I then gave this advise on my experience which may or may not be of value

  12. #12
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    Quote Originally Posted by Bros View Post
    I was just echoing my problems with the oven I had to do recently which required 6mm cable in the tiniest of J boxes the distance was so short it would not have been possible to put lugs on as there would have been to much strain on the lug from the bend needed in the cable.

    Why they went away from the old way beats me as you had plenty of room for terminations.

    I then gave this advise on my experience which may or may not be of value


    HI Bros

    I understand your point
    Sometimes things are not so easy as some sem to believe


    PeterQ

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    Default Re: Downsizing electric oven. Smaller cable required?

    Quote Originally Posted by oldtrack123 View Post


    [2[]Beware of old computer leads , many are not 10A rated.
    Very quicky melt the insulation if used on 10A loads!!!


    t
    Whilst this is theoretically true the duty cycle of an electric jug and the portable lead being run generally unenclsed in air means that even a 0.75mm2 iec lead will gennerally suffice.

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    Quote Originally Posted by koshari View Post
    Whilst this is theoretically true the duty cycle of an electric jug and the portable lead being run generally unenclsed in air means that even a 0.75mm2 iec lead will gennerally suffice.
    Hi
    Sorry but have seen the result
    Dickhead Ex son inlaw played with PCss & had some spare leads
    Daughter's jug cord played up, so he solved the problem with one of the PC leads
    He turned the jug on a left the room

    Daughter smelt plastic burning, got there just as it finally shorted out & tripped the breaker
    But her nice wooden bench top was a mess, molten plastic & burn marks!!!
    The insulation had melted from end to end!
    I have a couple of those myself so gave it a go on our jug
    ,I had to switch it off long before the jug boiled


    THe intersting thing is how were they ever allowed??

    The Aus Standards stipulate the cable rating cannot be less than the plug rating!!!

    PeterQ

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    As someone who has been there, done that with overloading cables (long story....) I very much doubt that the lead that melted was 0.75mm.

    Run 10A through a 0.75mm lead and it gets very warm, but I've done it for several hours continuously and nothing melted - it just got to "shower temperature" so maybe 40 - 45 degrees on the outside of the cable and it appeared to be unharmed. Likewise running 15A through a 1mm lead doesn't melt it either as long as it's not coiled up or covered etc and the ambient temperature is reasonable. Been there, done that.

    I'm guessing that those computer leads aren't 0.75mm. More likely they are 0.5mm or even less if it is melting so quickly that a 10A jug doesn't boil before the lead melts.

  16. #16
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    Quote Originally Posted by Smurf View Post
    As someone who has been there, done that with overloading cables (long story....) I very much doubt that the lead that melted was 0.75mm.

    Run 10A through a 0.75mm lead and it gets very warm, but I've done it for several hours continuously and nothing melted - it just got to "shower temperature" so maybe 40 - 45 degrees on the outside of the cable and it appeared to be unharmed. Likewise running 15A through a 1mm lead doesn't melt it either as long as it's not coiled up or covered etc and the ambient temperature is reasonable. Been there, done that.

    I'm guessing that those computer leads aren't 0.75mm. More likely they are 0.5mm or even less if it is melting so quickly that a 10A jug doesn't boil before the lead melts.

    Hi Smurth
    You may well be right, I did not check the actual cable size, nor did I suggest any size

    They were obviously not 10A [noticably smaller overall diameter

    I just quickly chopped all of his & mine up & dumped them.

    I stiill do not understand how they were allowed on the market .


    PeterQ

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    Default Re: Downsizing electric oven. Smaller cable required?

    Quote Originally Posted by oldtrack123 View Post
    Hi Smurth
    You may well be right, I did not check the actual cable size, nor did I suggest any size

    They were obviously not 10A [noticably smaller overall diameter

    I just quickly chopped all of his & mine up & dumped them.

    I stiill do not understand how they were allowed on the market .


    PeterQ
    Of course there werent .75 because .75 as I posted would handle 10a for the duration of a jug boiling with ease.

    I hsve for the record seen clover leads with cable that would be lucky to be .5mm2. Black and white core stuff.

  18. #18
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    Quote Originally Posted by oldtrack123 View Post
    Hi Smurth
    You may well be right, I did not check the actual cable size, nor did I suggest any size
    A previous post by someone else did suggest 0.75mm - I was replying to both you and that one at the same time.....

    Anyway, at a guess they would be 0.5 or even 0.3 mm - they are uncommon but I've come across such cables in the past. Suffice to say that I'm not keen on them.

  19. #19
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    Quote Originally Posted by Smurf View Post
    A previous post by someone else did suggest 0.75mm - I was replying to both you and that one at the same time.....

    Anyway, at a guess they would be 0.5 or even 0.3 mm - they are uncommon but I've come across such cables in the past. Suffice to say that I'm not keen on them.

    HI Smurf ]
    But the real qestion is, how were they ever left on hte market with a 10A plug fitted
    Defintely not compliant to Standards
    The plug shall not be of higher rating than the cable!!or words to that effect!!


    PeterQ

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