welding plugs

[bergie]

a 3 phase socket outlet that is only used for a welding machine. should it be on earth leakage? its a dedicated plug for the welder, but it's still a normal 4 pin plug.

[AndyD]

0142 states any plug and socket must be on rcd. This would include a three phase welder socket. If you change the socket for a t/pole isolator and hard wire the cable into it then RCD protection is then optional.

[bergie]

the single phase plug with flat earth doesnt have to be on earth leakage ,so if i use the 3 phase plugs with the guide pin which is off centre then it should be fine as a dedicated plug .

[AndyD]

Hmmm, I'm not sure off hand if you could run a welder on a 'red type socket' without an RCD or not.

[Sparks]

6.7.5.2 Industrial type single-phase and three-phase socket-outlets
(including "welding" socket-outlets) shall comply with the requirements of
SANS 1239 (SABS 1239), and, except as allowed in 6.7.5.5 and 7.10.1.6,
shall have earth leakage protection if the circuit is intended to supply portable
or stationary class I appliances.

A dedicated circuit may be installed without ELCB protection for a fixed appliance provided it is labelled as such.

A 3phase appliance which also utilises the neutral for control gear must have 4poles to comply with the regs.

[bergie]

i went to site to do the inspection and i see the plugs are on earth leakage protection,but i queried the 80 amp c/breakers.,but afterwards i added 25 % onto 63 amps then its very close to 80 amps. i must just check the cable size.theres 36 circuits so it will be a bit expensive to do mods.

[mikilianis]

Hi bergie not wanting to be sounding ignorant but what is the 25% for

[Sparks]

Am also baffled, but don't know whole story so I just left it.

[bergie]

Am also baffled, but don't know whole story so I just left it.

i havent looked in the book for exact reference,but the circuit breaker+cable size for socket outlets is restricted to 125% of the rating of the socket outlet.
16 amp s/o = 20 amps,2,5mm
32 amp s/o = 40 amp 6mm wire
and then the 63 amp s/o = 79 amps (close enough to 80 amps)
there are 16mm cables installed,which can supply 80 amps under certain conditions.
so i accepted it on principle so far.

[Sparks]

I see what you are looking at. Just keep in mind that you are not just limited as to the current you can supply to a socket outlet but also remember that your cable has a limit and that limit governs the max for your circuit breaker. The circuit breaker would also normally have a 5% tolerance unless you use a speciffically designed CB with a higher tolerance or delay for high startup demand applications.
In a nutshell let the circuit gauge guide your choice of CB strength and if that is not high enough for you, put in another circuit. Also, do not expect a circuit carrying max capacity to last. I am sure you do not ride around in first gear all day. Don't forget to check the kVA rating as well.
You spoke of 36 circuits, are they all welding circuits? How many welders will actually be used at the same time max? What is the max consumption at the busiest time? What is the max load for each circuit? There is a lot to take in consideration to get it right. A plug circuit is not just a plug circuit.

[bergie]

hi sparks
theres 2 plugs on a circuit : 63 amp 4 pin with 16mm cable and 80 amp 3 pole. the cable is about 10m. its been working fine for years ,but they need a coc. 2 welders on a 1 circuit trips a 63 amp breaker if they strike at the same time.they have 400 amp busbars(sealed ) running along the factory and they tap off circuits where they want with a breaker+ earth leakage under the busbars. some places are fuses under the bus bars for other machines.
i dont like the system,but i cant fault it. for interests sake,they have a huge 1500 amp oven with its own mini sub. factory dates back to 1950,s i think.

[Sparks]

With such big welders I suggest you check what the actual maximum load is with a simultaneous strike and let that be the deciding criteria. From what you have said so far I would consider having each plug on it's own circuit. There is no control as to when the welders will strike at the same time and it would cost them more to keep resetting a breaker that will not last long. Cater for startup load not running load unless you use a delayed breaker. That will cater for occasional simultaneaous strikes. Measure it & know the exact demand. Then you cannot make an expensive/dangerous mistake.