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Thread: 10A and 15A circuits

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    Default 10A and 15A circuits

    Okay I have a garage which has just been a storage shed for years and i've decided to turn it into a workshop. I'll be starting with a 3HP table saw but there is only a single 10A circuit in it.

    When I get a new 15A circuit installed to it am I able to safely use 10A equipment on it or can they only be used on the 10A circuit?

    This house also had an electric oven hardwired when we got it but we changed it to gas. Instead of getting a 2nd 15A circuit installed in the garage, can this one the oven was on just be extended to the garage or is something about it different because it was hardwired and won't be suitable for plugging in 15A machinery?



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    i used the old 15a stove circuit to run to my garage about 45yrs ago without any problems

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    I did the same with a unused 15amp power point for an old heater, it should be ok as long as the shed is not too far away

    there is some info here

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    When I had a stove installed eons ago, a separate circuit was installed with 50 Amp fuse (Single Phase) BUT the lead used was only two core, the Earth for the stove was run as a BARE multi strand copper wire to the meter board and 'Ground' connection.
    The house had been originally wired using conduit and 2 fuses were provided.
    The House was divided into TWO circuits, each included LIGHT and POWER.
    If you blew the fuse on 'A' side, 'B' still had Light and Power.
    The Conduit contained 2 cotton over rubber covered nickle steel multi strand wires with a BARE multi strand wire for the earth laid separately across the ceilings.

    Isnt the only danger using a 10A devise on a 15A circuit is may suffer more damage if it fails because the Fuse may not blow as quickly?

    But then again, how many 1 to 5A devises do you have plugged into a 10A circuit?

    This is where the UK system of having a fuse in each devise shows its value.
    Much of the wiring (Power) has been replaced to the more later safer version but I dont have A.N.E connections at each LIGHT connection so installing a ceiling fan has to be wired individually.

    I should have added, If your NOT happy with the situation and your not capable of checking it yourself, get an Electrician in to do it for you.
    Last edited by gordon_s1942; 26-04-18 at 01:37 PM.
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    I should have added, If your NOT happy with the situation and your not capable of checking it yourself, get an Electrician in to do it for you.
    +1
    A 10A device will happily work on a 15A circuit typically most devices only draw an amp or 2 anyway. Remember a 10A breaker (or fuse) is designed to cover the TOTAL load of the circuit not just individual devices. A stove is usually the only device on its circuit because it, alone, is capable of drawing nearly that amount of current. In the same manner, Air conditioners are given their own circuit for similar reasons. The sparkie who does your wiring will be able to advise. As for the Oven circuit, yes, the breaker may well be ok to power the shed, but recovering the cable and re-running it is just plain uneconomical.
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    Power circuit wiring is 2.5mm^2 copper which is good for as much as 25A depending on how thermally insulated it is. That rating comes down if it's buried in thermal insulation but still good for about 20A so there's no problem having a 15A outlet on the end of it (just one outlet that is). The wiring rules allow for a diversification of loads on a single circuit so you can have multiple 10A outlets on a single run of 2.5mm^2 wiring and just need to be mindful of the total demand on a single circuit at any one time EG running a kettle + toaster + steam iron + room heater and a welder simultaneously puts the load way over the max rating and probably would trip the circuit breaker. If you have a mixed final sub-circuit (lighting + power) such as you'd have in a shed or outside workshop I think the current rules require much larger wiring like 6.3mm^2, not sure if that applies to all states though.

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    Quote Originally Posted by gordon_s1942 View Post
    When I had a stove installed eons ago, a separate circuit was installed with 50 Amp fuse (Single Phase) BUT the lead used was only two core, the The Conduit contained 2 cotton over rubber covered nickle steel multi strand wires with a BARE multi strand wire for the earth laid separately across the ceilings.

    Isnt the only danger using a 10A devise on a 15A circuit is may suffer more damage if it fails because the Fuse may not blow as quickly?
    There's probably still some old installations wired with that rubber insulated cable but by now it's a major death and fire trap. I encountered it like over 30 years ago in a house built in '46 where the insulation could be crumbled off with a finger and that wiring was run in steel conduits so it probably got replaced in the nick of time.

    Fuses are very unpredictable protection in the best of cases, rewirable type fuse wedges being the worst. A wired fuse is intended to 'blow' at around 150% of the circuit's max rating so a 2.5mm^2 power circuit will have a 15A fuse which hopefully will go open circuit at 20-25A so the wiring (particularly its insulation) is not damaged by prolonged overloading.

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    Quote Originally Posted by Skepticist View Post
    There's probably still some old installations wired with that rubber insulated cable but by now it's a major death and fire trap. I encountered it like over 30 years ago in a house built in '46 where the insulation could be crumbled off with a finger and that wiring was run in steel conduits so it probably got replaced in the nick of time.

    Fuses are very unpredictable protection in the best of cases, rewirable type fuse wedges being the worst. A wired fuse is intended to 'blow' at around 150% of the circuit's max rating so a 2.5mm^2 power circuit will have a 15A fuse which hopefully will go open circuit at 20-25A so the wiring (particularly its insulation) is not damaged by prolonged overloading.
    Found the same thing when I was assisting the brother in law (licensed elecco) to install a light fitting in the wife's, grandmothers place. The job turned into a complete house rewire .

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    Quote Originally Posted by Skepticist View Post
    Power circuit wiring is 2.5mm^2 copper which is good for as much as 25A depending on how thermally insulated it is.
    AS3000 has meant 2.5mm has only been good for 16amps for around 15 years now
    (Any wall is considered insulated now, whether it has insulation or not)
    Gone are the days of 20Amps (aka HWS) and 25amps was a theoretical max, but couldn't be installed and used as such in practise to my knowledge.

    For Sheds and Garages, i suggest people have a Min of 6mm sub-main to the Shed/Workshop (that is also another AS3000 rule) if having a Switchboard out there (highly recommended)

    Then i suggest 2.5mm Orange Circ for everything (lights and power)
    1: It prevents them from f#$king up
    2: Where ever this is a cable, they can add a PP later (which always happens)
    3: If you are running Hi Bay lights, you don't get far with a normal 10Amp lighting circuit, so having a 16Amp circuit helps with loading
    4: If it is a shed with a lot of exposed C-section steel work, Orange Circ offers much higher mechanical protection, even if using conduit as well.
    Last edited by ol' boy; 04-05-18 at 05:01 PM.
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