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Posted By Topic: Building 3 Phase extensions leads

ShaneR
Mar 06 2018 09:21

Hi all

Just wondering about 3 phase flex extension lead cable sizing?

AS/NZS 3008 Table 16 looks like the correct place.


We know the appliance limits the current so we can put a bigger plug on the end?

e.g. My factory has 32amp 3P plugs everywhere and all my 3P appliances have 32amp plugs. (assuming all appliances are less that 32A)


I\'m answering my own question as I type.

If the supply plug is rated 32A the extension cable must also be 32A rated but the cable hard wired to the appliance may be smaller (appliance rated) with a bigger plug?

I also note that table 16 only goes to 25Amp?


   

pluto
Mar 06 2018 11:03

Table 1 of as/nzs 3012 also gives current currents and maximum lenghts for a specified volt drop.

Flexible cords and flexible cables use different tables of as/nzs 3008.1.2 see AS/NZS 3012 notes and clauses near table 1 in AS/NZS 3012 for further details.
   

ShaneR
Mar 06 2018 13:33

\"AS/NZS 3012\" to me didn\'t really help?

20amp max?

maybe I missed something?
   

AlecK
Mar 06 2018 14:29

You may well find that some of or maybe all of those 32 A sockets around the factory can\'t actually supply 32 A. But nothing unsafe or non-compliant about that, provided the subcircuit cable is properly protected.

Equally nothing wrong with an appliance having a bigger-than-necesary plug; but \"electrically unsafe\" to have a plug smaller than FLC of appliance.

When it comes to leads, yes the flex should be rated at least as high as the rating of the plug. Can have a connector of equal or smaller rating than plug; but not higher.
   

ShaneR
Mar 06 2018 15:39

\"When it comes to leads, yes the flex should be rated at least as high as the rating of the plug. Can have a connector of equal or smaller rating than plug; but not higher.\"


Thank you


Never really thought about it before

The extension lead cable size is determined by the \"plug\" rating but the \"socket\" end can be equal or less than the \"plug\" rating.

or

Use a lead with a circuit breaker like the caravan ones? (never seen a 3 phase one)
   

AlecK
Mar 07 2018 09:25

Yes that\'s a valid option