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  #2682811 29-Mar-2021 23:01
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There are two main limits on sizing cable. Thermal is the same regardless of length. It basically comes down to how much heat is produced per meter of cable, vs how much heat can be dissipated per meter of cable. This doesn't change whether it's one meter or 100, although it is affected by environment (clipped surface, in a wall, surrounded by insulation, underground etc.). On short lengths, this is the main determining factor.

 

Second is volt drop, generally you want no more than about 2.5% in a subcircuit. The longer the cable, the more volt drop, and eventually you'll have to go up a size.

 

The reason you can have stupid numbers of hotpoints on a circuit is that if the user tries to load them past the 16/20A of the breaker, the breaker cuts the power and lets the cable cool down, given some caveats around sustained loads, trip curves, and accuracy.




MadEngineer
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  #2682812 29-Mar-2021 23:06
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Hard to tell from that picture but hopefully the cable meets the minimum conductor diameter and cable size if you use a 56 series connector.




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andrewNZ
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  #2682813 29-Mar-2021 23:07
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The welder should have a rating plate on it. One of the values should be "I eff" (effective current) this is the value to size the connection with.

Those little welders aren't usually rated to pull full current continuously, the "I eff" rating is a bit like a maximum demand calculation.


Edit: The circuit protection should probably be suitable to handle the peak current to prevent neusence tripping
The welder lead and plug need to be sized for I eff.



WanaGo

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  #2682819 29-Mar-2021 23:23
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andrewNZ: The welder should have a rating plate on it. One of the values should be "I eff" (effective current) this is the value to size the connection with.

Those little welders aren't usually rated to pull full current continuously, the "I eff" rating is a bit like a maximum demand calculation.


Edit: The circuit protection should probably be suitable to handle the peak current to prevent neusence tripping
The welder lead and plug need to be sized for I eff.


Thanks. In my first post I wrote it, 21A is the I eff. I max is 40A. I nominal is 30A.

WanaGo

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  #2682820 29-Mar-2021 23:26
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MadEngineer: Hard to tell from that picture but hopefully the cable meets the minimum conductor diameter and cable size if you use a 56 series connector.


OD of the cable is just under 10mm
Conductors are 3.31mm2 AWG12

WanaGo

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  #2682821 29-Mar-2021 23:29
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SomeoneSomewhere:

There are two main limits on sizing cable. Thermal is the same regardless of length. It basically comes down to how much heat is produced per meter of cable, vs how much heat can be dissipated per meter of cable. This doesn't change whether it's one meter or 100, although it is affected by environment (clipped surface, in a wall, surrounded by insulation, underground etc.). On short lengths, this is the main determining factor.


Second is volt drop, generally you want no more than about 2.5% in a subcircuit. The longer the cable, the more volt drop, and eventually you'll have to go up a size.


The reason you can have stupid numbers of hotpoints on a circuit is that if the user tries to load them past the 16/20A of the breaker, the breaker cuts the power and lets the cable cool down, given some caveats around sustained loads, trip curves, and accuracy.



Good Info, thanks.
This will be run in plastic electrical conduit along the wall and into the fuse box.
Just measured it out a bit more accurately and my initial guess was decent, actual measures 6.5m so say 7m once it has some tails on each end.

  #2682826 29-Mar-2021 23:36
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OK. Run in surface conduit, 4mm is adequate but it's really not going to save you much.


 
 
 

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Danite
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  #2682830 30-Mar-2021 00:14
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No chance of getting a 32A outlet wired to 2.5mm, best you can get legally is 25A out of 2.5 under very specific circumstances.

WanaGo

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  #2682832 30-Mar-2021 00:33
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Going to go with 6.0mm TPS - better to be safe than sorry, and means something else (bigger) in the future might be able to use the same socket, or at least the same cable run with a different socket.

 

Thanks everyone


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