Online assistance for electrical trade people in New Zealand and Australia Login  |  Register  |   Forgot Password
Assistance for electrical trade people
 

 

 

 


Click here to send Ron a pdf document for publication on this Topic

Documents must be less than 200k in pdf format

Posted By Topic: 15-amp flat pin plug

voltaire
Oct 27 2018 16:50

My welder has a 15-amp flat pin plug, which fits nicely in the flat pin 15-amp socket in my workshop. And ONLY in that socket, because its earth pin is ~9mm wide, whereas the normal 10-amp lug\'s earth pin is ~6mm wide.

However, the phase and neutral pins are exactly the same on New Zealand\'s 10- and 15-amp plugs.

HUH? The only plugs carrying current are, of course, the phase and neutral. The earth pin carries a current if and only if there\'s an earth fault. Then the earth pin might carry a high current, but for only milliseconds before the ELCB trips out.

So if the phase and neutral pins on a 10-amp plug are the same size as on a 15-amp plug, the powers-that-be must deem them to be perfectly capable of carrying 15 amps—so why do we have to have a different plug where the only difference is a pin that doesn\'t normally carry any current at all?

Clearly if the phase and neutral pins are the same size then the contact area is the same. The only difference I can imagine is that the socket contacts might be made a bit thicker in the 15-amp socket to help with additional heat dissipation. (I haven\'t taken a socket to bits to check this.)

So what\'s the rationale here, Ron?
   

pluto
Oct 27 2018 17:46

voltaire Oct 27 2018 16:50

Your commentn
My welder has a 15-amp flat pin plug, which fits nicely in the flat pin 15-amp socket in my workshop. And ONLY in that socket, because its earth pin is ~9mm wide, whereas the normal 10-amp lug\'s earth pin is ~6mm wide.

However, the phase and neutral pins are exactly the same on New Zealand\'s 10- and 15-amp plugs.

HUH? The only plugs carrying current are, of course, the phase and neutral. The earth pin carries a current if and only if there\'s an earth fault. Then the earth pin might carry a high current, but for only milliseconds before the ELCB trips out.

So if the phase and neutral pins on a 10-amp plug are the same size as on a 15-amp plug, the powers-that-be must deem them to be perfectly capable of carrying 15 amps—so why do we have to have a different plug where the only difference is a pin that doesn\'t normally carry any current at all?

My comment
In AS/NZS 3112 which is the applicable standard for 3 pin flat plugs and sockets there a series of plugs and sockets with current ratings of 10, 15 and 20 amps,

10 amp all pins are the same size

15 amp the active and neutral pins are the same size as for the 10 A plug and the earth pin is larger,

20 amp all pins are the same size as the earth pin on the 15 A plug.

The testing required for certification purposes to permit sale in NZ, are all done at the marked current rating + a small additional margin. You can be assured that the plugs and sockets can carry the current without any undue heating of the contacts (up to a specified temperature limit).

The combinations of the plug pin and socket slot sizes is used as a means of ensuring that a

10 A socket will prevent the entry of a 15 or 20 A plugs only

15 A aocket will accept a 10 A or 15 amp plugs and prevent the entry of a 20 A plug

20 A socket will accept the entry of a 10 A, 15 A or 20 A plugs.




   

toyoto
Oct 27 2018 20:07

The 15amp socket has beefier internals to handle the extra current and putting a larger earth terminal on a plug means it can only be inserted into a 15amp socket.

The pins on the plug could handle a lot more than 10 or 15 amps, it\'s the internals of the socket that you can\'t see which are bigger
   

voltaire
Oct 28 2018 09:23

Thanks, Toyoto.
That certainly explains it.
   

SteveH
Oct 28 2018 10:12

\"So if the phase and neutral pins on a 10-amp plug are the same size as on a 15-amp plug, the powers-that-be must deem them to be perfectly capable of carrying 15 amps—so why do we have to have a different plug where the only difference is a pin that doesn\'t normally carry any current at all?\"

\"The 15amp socket has beefier internals to handle the extra current and putting a larger earth terminal on a plug means it can only be inserted into a 15amp socket.\"

The other difference that you can\'t see voltaire,is the size of conductors and MCB supplying your 15Amp socket, these will have been selected to be capable to supplying 15 Amps continuously.

If the installing electrician knew you were going to run a welder from the outlet, the size of conductors should match the maximum current rating of the welder.

Frequently, the makers/suppliers of welding equipment sell their products with plugs that come nowhere near matching the Ieff rating of the appliance, they then put a tag on the lead stating that the plug fitted is for \"demonstration purposes only\" and the user is responsible for getting a plug of the correct rating fitted for their intended use. Or, the rating plate comes in two versions, one for the lead and plug fitted, and then one that lists what\'s needed to fully utilize the item.

Great pity that the good folk at Energy Safety are too busy working on their risk matrix engine to look at what\'s going on out in the market place.


   

voltaire
Oct 28 2018 12:21

Steve, the 15-amp single outlet is run off the same 2.5sq mm supply as the double 10-amp sockets in the rest of the workshop. And they\'re all supplied via a 20-amp breaker.
   

Satobsat
Oct 28 2018 14:38

2.5mm square CSA cable may be suitable for the length of the circuit. How long is the cable run between the socket and the switch board it is supplied from? Taking in to account the vertical runs as well as the horizontal.