The outlets are built like... outlets, with individual switches and beefy screw terminals. Plus, the internal busbars are centre-fed, with two sockets on each side of the tee. I don't really see why they're not rated for 20A total; they're mechanically identical to the 15A versions and the busbar is fairly sizeable compared with cabling.

Power boards include a plug/socket that takes the full load, along with flexible cable. That has a strict temp limit. The busbars are also end-fed, and as you've found, the thermal breakers are not the most reliable. Plus, being potentially mobile rather than fixed, the plugs and contacts are exposed to more strain.

But if you take the 10A rating as gospel... cabling is part of the installation, and must be protected from overload. Same goes for switches. Individual sockets, while they may be 10A on a 20A+ circuit, are protected from overload by the requirement that devices with a 10A plug be designed not to exceed 10A load. Even socket RCDs (like you find in bathrooms occasionally) are explicitly rated for 20A through-connection of further loads down the line.

But we don't seem to consider what protects the socket assembly from exceeding its 10A rating. This applies to every double socket except for the ones that are two separate double sockets on one plate, like some old Clipsal versions.

I believe it's just an extension of the rules that allow for unprotected double adapters and tap-on plugs, and assume that end users probably won't overload them that often or severely (and even then,they have labels like "10A total load". But it irks me.

SomeoneSomewhere:

 

Yup, quad outlets are the preferred option for this. Readily available in black. Both legrand and PDL Iconic seem to be only producing horizontal versions, so if you need vertical, you'll need to go with the 600 series - might match better with existing anyway.

 

https://eref.se.com/au/en/pdl/product-pdf/PDL395H4C-XB

 

https://eref.se.com/au/en/pdl/product-pdf/PDL641BK

 

Amusingly, both double and quad outlets are generally only rated for a total combined load of the highest-rated socket, so still only 10A in this case... but unlike a 10A power board, have no protection enforcing this. I have no idea why this is legal but *shrugs*. It's not actually going to have any impact on loading and there aren't the sustained 20min+ loads that tend to cause failure. They used to make /15 versions that had 3x10A sockets and 1x15A socket, but these appear to be discontinued.

 

Looks like the newer iconic line doesn't include a quad vertical; the old 641s should still be available and might better match existing anyway.

 

Yes, they can be surface mounted, but the normal method of mounting them only requires a small recess in the centre similar to a standard double plug - drilling out the recess to be larger is also possible.

 

Mounting an additional double outlet (preferably surface) immediately next to the existing one should also be easy.

 

 

 

A quad outlet on a single circuit would just blow the circuit breaker if you tried to run a jug, toaster, microwave and fan heater a the same time. 

SomeoneSomewhere:

 

The outlets are built like... outlets, with individual switches and beefy screw terminals. Plus, the internal busbars are centre-fed, with two sockets on each side of the tee. I don't really see why they're not rated for 20A total; they're mechanically identical to the 15A versions and the busbar is fairly sizeable compared with cabling.

 

the 10amp version are often thinner metal than the 15amp versions. manufactures skimp as much as they can on mass produced items. 

johno1234:

 

A quad outlet on a single circuit would just blow the circuit breaker if you tried to run a jug, toaster, microwave and fan heater a the same time. 

 

That is what you should hope for. Overloading the circuit like that with the breaker not blowing could cause some serious harm.

Get a quad outlet with a switch on it for the waste disposer and remove the extra isolation switch?

https://www.kiwisparks.co.nz/products/395h4xx-quad-gpo-2-switches

johno1234:

Get a quad outlet with a switch on it for the waste disposer and remove the extra isolation switch?

https://www.kiwisparks.co.nz/products/395h4xx-quad-gpo-2-switches

 

Yup, double with extra switch is an option.

However, some sparkies don't like putting two different circuits in the same box. It is permissible, but you need a label saying that it's fed from two (or more) sources of supply* behind the plate so anyone opening it up (including dumb homeowners who buy the place off you in 15 years) know to be extra careful.

This of course only applies if it's actually two different circuits.

As for wattage/high demand, the rule (generally) is one per plate (be it single, double or quad outlet, switches in the outlet don't count), two per circuit. Kitchens generally have two or more circuits, depending on how much the person doing the work cared on the day. 

* There is mild debate here as to whether this uses the legal definition of a point of supply, meaning that the label would only be necessary if fed from two separate supplies; generally say two different houses/flats/tenancies, or a mains supply and a generator supply. Better to stick the label in there, especially since it can just be sharpie on the actual plate, hidden by the cover plate. 

Eva888: Makes sense. I also thought that maybe you can get a labelled switch for the disposal. Will talk to my new sparkie beforehand. Thanks all. Another learning experience on GZ

You can. 

https://www.electricaldirectltd.co.nz/product/1912-PDL-20Amp-Switch-Module-WASTE-Choose-Colour