DOL switches and overload protection

[LuckyDuck]

(I had posted this thread in another section before realising that it probably fits better under electrical; thanks for the help...)

I just purchased a 4hp, 3kW, 3phase motor for my table saw as an upgrade. The plate on the motor says it pulls 4.8-5.3Amps (~415V). My electrician reckons I need a 20Amp DOL switch with overload protection with a range of 4.5-6.5Amps.

But when I went to source a switch with these specks from the NHP range, I was informed that the overload protection specified seemed very low for such a large (i.e. 20 Amp) switch. They questioned whether I really needed a 20 Amper...? I was also told that such a switch is quite costly ($300 range).

What is the go here? Do I really need a 20Amp switch? And how do I tell what size switch I do need. I suspect that my electrician errs on the side of "overkill" which suits my personality. But I don't want to be ridiculous and spend money unnecessarily.

Any help is greatly appreciated! Regards, Luckyduck
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[Redgy]

20A is for the start up current which is roughly 6X full load current. The best thing for the job is a DOL starter, which is a contactor with overload in a box with a stop/reset & start button. The stop button is a mushroom type so you can find it quick if need be (I stop mine with my knee) It also acts as a no volt switch such that when the power goes off & comes on again the saw wont fire up. All your sparky has to do is stick 3phase in the top & motor cable out the bottom & the job's done, all the 'control' wiring is pre-done. Try a Clipsal 56DOL9. This is for a 4kw with a 6-10a overload built in & YES is prolly around the $300 but for motor protection & the safety angle it's the go.

Redgy

[LuckyDuck]

Redgy,

Thanks very much for the input. It's good to have confirmation on the switch specs and price. Tah! Regards, Luckyduck