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Is there any difference between a 10A and 15A GPO?

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  1. #1
    2K Club Member chrisp's Avatar
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    What is the difference between a 10A GPO and a 15A GPO?

    There has been much discussion on other threads about the differences and similarities. Some have suggested that 15A GPOs are more durable and less likely to melt or burn at 15A than a 10A GPO. Others have suggested that the internals are probably the same but with a different face plate. I thought it would be interesting to look inside both a 10A GPO and a 15A GPO to see if there are any differences.

    The most common 10A GPOs are a double outlet variety, but as 15A GPOs are only available as a single outlet, I thought it would make more sense to compare a 10A single GPO with a 15A GPO. The brand and model/series were also kept the same. I choose a brand and model that is popular in Australia and commonly used by electricians. The samples are from a "trade" pack as purchased by electricians rather than the "retail" package version as sold in some hardware shops.
    Figure 1 shows a front view of the two GPOs. The 15A unit is on the right. Notable differences are the size of the Earth socket and the "15A" in black on the switch of the 15A version.

    gpo-fronts-small-.jpg

    Figure 2 shows a rear view of the two GPOs. Again, the 15A unit is on the right.

    gpo-backs-small-.jpg
    Notable difference are that on the 15A unit there is an extra tab of black plastic below the Earth pin. The colour rings are also slightly different: On the 10A unit the colour rings (Green on the Earth and red on the active) are full circles; Whereas on the 15A unit they are half circles. Although not apparent in this photo, the white front plate of the 15A unit also has a moulded section that mates with the extra tab of the black plastic.
    Figure 3 shows the back of the 10A unit. The colour rings on the Earth and active can be seen.

    gpo-10a-back-small-.jpg

    Figure 4 shows the back of the 15A unit. The colour half-rings on the Earth and active can be seen. In this photo it is also possible to see the extra section on the white front plate that mates with the tab on the black plastic.

    gpo-15a-back-small-.jpg

    Figure 5 shows the 10A GPO with the front plate removed.

    gpo-10a-internal-small-.jpg

    Figure 6 shows the 15A GPO with the front plate removed.
    Notable differences are: that the 15A unit has the extra tab below the Earth pin; the 10A unit has "15" embossed in it whereas the 15A unit has "15 N" embossed; the 15A unit has "15A" on the switch.

    It seems that the moulding used in this particular sample of a 15A GPO is also designed to accommodate a neon indicator (maybe this is what the embossed "N" means?).

    It is not obvious in the photos, but the Earth metal work in the 10A unit is not fixed to the black plastic and can readily be removed. Whereas in the 15A unit the Earth pin metal work seems to be fixed to the black plastic by slight flaring of the screw connector.

    The two plastic sections in the 10A and 15A GPOs are different. The front covers obviously have different size openings for the Earth pins; and the 15A unit also has the extra tab below the Earth pin. It is hard to tell if the other differences are functional. For example the 15A unit used here has provision of a neon indicator but the 10A unit doesn't. Both units are available with a neon indicator. Also, the differences in the way the Earth and active colours are applied seems to suggest that these units maybe from a different manufacturing batch, or that perhaps the design has been changed at some stage.

    The size of the Earth contacts/wipers seem to be identical in both units. There doesn't seem to be any difference in the contacts of the Earth socket in a 10A GPO and the Earth in a 15A GPO.
    Figure 7 shows the switch removed from the 15A GPO.

    gpo-15a-switch-small-.jpg
    There doesn't appear to be any difference in the between the switch mechanisms of the 10A and 15A GPOs.
    Figure 8 shows the 10A GPO with the switch mechanism removed.

    gpo-10a-disassembled-small-.jpg
    Figure 9 shows the 15A GPO with the switch mechanism removed.

    gpo-15a-disassembled-small-.jpg
    The "rocker" plate of the switches can be seem near the bodies.

    Not shown in the photos, but the "rocker" plates have a slot indentation stamped into the other sides that is part of the locating mechanism. The size of the plates was measured to be:
    10A unit: 13.02 x 6.32 x 1.22 (mm)
    15A unit: 12.97 x 6.40 x 1.26 (mm)
    It is hard to tell if the slight size differences are due to manufacturing tolerances; units being of different batches; or caused by slight distortions due to stamping the slot in the other side.

    Looking closer at the active (a pun, but quite appropriate in this case) components.
    Figure 10 shows the "switched active" removed from the 10A GPO.

    gpo-10a-active-small-.jpg
    The "switched active" of the 15A GPO also can be removed the same way as shown in Figure 10.

    The size of the "switched actives" of both GPOs were measured to determine if there is any differences.
    Figure 11 shows the width of the switched-active in the 10A GPO at the narrowest part (5.88mm).

    gpo-10a-width-small-.jpg
    Figure 12 shows the thickness of the switched-active in the 10A GPO (0.68mm).

    gpo-10a-thickness-small-.jpg
    Figure 13 shows the width of the switched-active in the 15A GPO at the narrowest part (5.88mm).

    gpo-15a-width-small-.jpg
    Figure 14 shows the thickness of the switched-active in the 15A GPO (0.67mm).

    gpo-15a-thickness-small-.jpg
    The size of these components seem to be identical within measurement error.

    An interesting difference was noted between the switched-actives of the 10A and 15A GPOs. Looking at Figure 15 it can be seem that the top the switched actives has what looks like a deformed, or mis-stamped switch contact. The upper switched-active is from the 15A GPO.

    gpo-10a-15a-contacts-small-.jpg

    Conclusions

    As far as I can tell from physical inspection and measurement, the internals of the 10A single GPO seem to be functionally identical to the internals of the 15A GPO.

    Does this mean that there are no differences internally between 10A GPOs and 15A GPOs? In this instance it seems there is little or no difference, but this could be because the manufacturer has decided to use 15A internals in the 10A single GPOs to reduce inventory.

    Do the 10A double GPOs have lighter internals than the single GPOs? I don't know.

    Disclaimer
    These posts are intended for general knowledge only. The author does not wish to imply that a 10A GPO can be used instead of the 15A GPO. There maybe differences with other brands or models. Do not use 10A GPO in place of a 15A GPO. It is illegal to do fixed electrical work in Australia unless licensed to do so.

  2. #2
    Tool Whore - 1K Club Member Vernonv's Avatar
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    Nice work Chrisp ... very thorough indeed.
    I must admit I'm not terribly surprised by your results. But as you have mentioned the results are specific to the examples used (high quality items from a respected manufacturer, by the look of them). Double GPO's might possibly be very different and I would bet that "cheap" GPO's would only have as much copper in them as they absolutely needed (for 10 amps).

    I guess it proves the point that manufacturers will always try and save costs by using the same parts in different but similar products, even if those products have different "nameplate specs" ... but they will of course charge you a premium for the higher "nameplate spec".
    Cheers.

    Vernon.
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  3. #3
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    dont blame the company vernon. Its more exppensive because they sell a whole lot less, so its a specialty item. The only reason they make them is because the stds have a different plug size to ensure that its differentiated from a 10 amp circuit - ie only one output for the circuit, and the appliance must be plugged in to a dedicated 15 amp circuit. it does make some sense.

  4. #4
    House Husband - 1K Club Member
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    I suppose if the current carrying components meet the requirements for the ampage carried they could be the same........ Then it would only be the external package that would have to be different. There is a cost saving right there. Look at the size of the pins on a British plug (240v) HUGE! and compare that to the size of the pins on most US plugs (110~120v) (thinner than Australian ones and more flimsy) Does actual sizes used by the above, translate to a safe current carrying capacity?

  5. #5
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    I spoke to my sparky about your 10A vs 15A observations.
    He believes they are both over-engineered to handle 20amps (if not more) and that the larger earth pin difference is merely to direct 15A appliances to 15A circuits.

    Thanks for your efforts in dissecting a myth.

  6. #6
    Heavy Machinery Claw Hama's Avatar
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    As your sparky said the 15 amp earth pin is just a "key" so you can't run your 15amp equipment on a lower rated cuircit (10amp) which generaly has a lower rated cable. As for current carrying capicity have a look at your normal 15amp fuse wire compared to the size of your power point pins. You would need maybe 50 - 100 amps to melt them.
    A good edge takes a little sweat!!

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  7. #7
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    Quote Originally Posted by Claw Hama View Post
    As your sparky said the 15 amp earth pin is just a "key" so you can't run your 15amp equipment on a lower rated cuircit (10amp) which generaly has a lower rated cable.
    The bit about the "key" is absolutely correct, the bit about the lower rated cable is less so.

    THe cable used to wire a 10A GPO is exactly the same as the cable used to wire a 15A GPO. In most installations, it would even come off the same roll!

    The difference between 10A and 15A GPo's is entirely to do with how they are used, not how they are made (and price differences are an "economy of scale" issue as noted previously by others).

    A 15A GPO is the ONLY GPO on the entire final sub-circuit (ie. the cable from the circuit breaker goes directly to the 15A GPO and nowhere else). It is for that reason, that a 15A load can be placed on a 15A GPO, which is usually connected to a 16A circuit breaker - and can thereby carry 15A without triping.

    A 10A GPO will usually be part of a "daisy-chain" of GPO's all connected to the same final sub-circuit, fed from another 16A circuit breaker. The theory is that most appliances will use much less than 10A, and even if you are using one that does, the rest of them in use at any one time more than likely wont. A normal sub-circuit of 10A GPO's is basically playing an avergages game sharing out its total capacity (16A before the breaker trips) between all the expected appliances. That's why sometimes if you plug 2 10A appliances into the same circuit, and they cycle on at the same time, you will trip a circuit breaker even if there is no particular fault with the appliances - 2 x 10A = 20A, and the breaker trips at 16A.

    Althought it would be completely illegal to do so, technically there would be no diferance between plugging a 15A welder (for example) into a 15A GPO, and filing down the earth pin so it would fit into a 10A GPO if you could guarantee that nothing else on that circuit was in use at the same time. Most folk simply wouldn't know which GPO's were on which circuit, so the risk of overloading a circuit would be too great. That is why 15A GPO's exist.

    Regards,

    pcal

  8. #8
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    i am not surprised at all most factorys you go to will have a 15amp plug with the earth pin grounded down to fit into a 10amp gpo

  9. #9
    Heavy Machinery Claw Hama's Avatar
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    Sorry pcal slip of the tounge, I ment the cable is down rated because it has multipul points on it not a smaller cable.
    A good edge takes a little sweat!!

    www.solidwoodfurniture.com.au

  10. #10
    ab1
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    I'm not too sure if there is a rule that say's one 15amp socket per circuit or if it is just common practice.

    I don't see why, in the situation of a shed at home, replacing a 10amp power point for a 15amp would be dangerous. As far as I know, the wiring regulations are mainly concerned about the protection of the cable.

    How many can you put on a circuit if the cable is 4mmor larger?? Still just one or multiple?

    At worst the circuit breaker would trip.

    Clipsal makes a 15amp double power point.

  11. #11
    Golden Member nev25's Avatar
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    Quote Originally Posted by ab1 View Post
    I'm not too sure if there is a rule that say's one 15amp socket per circuit or if it is just common practice.

    .
    It depends on what else is on the circuit
    AS/NZ3000 2007 table C8

  12. #12
    owner builder
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    Rather than filing down a 15 amp plug, I read that you are better creating an adapter in the form of an extension cord. That way you don't void the warranty. Sounds dodgy though - better leave it up to the experts .

  13. #13
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    The findings above do not surprise me the least I heard rumours circulating years back that the internals were the same and even heard the light switch mechs are internally the same except one has 15 a stamped and the other 10amp on the mechanism rocker

  14. #14
    Apprentice (new member) billrule's Avatar
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    That reminds me, having had some issues with light switches, I changed the mechanisms from 10 to 15 amp. The mechanisms felt significantly heavier to use, but I suppose that the older 10 amp units could have lost some of their spring tension over their lives to that point. The strength of spring alone would probably determine the "feel" of the switch in action.
    great work CHRISP; anyone would think you were a scientist

  15. #15
    Golden Member nev25's Avatar
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    Quote Originally Posted by billrule View Post
    , I changed the mechanisms from 10 to 15 amp.
    WHY???


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