3 phase allows two different connection schemes with two different power levels, and neither of them needs a neutral. The Delta arrangement has been already mentioned, but the WYE connection reduces the power quite a bit. The downside of the WYE without a neutral is that the power drops a lot if one leg fails, and if the loads are different then the center is not quite neutral.

 

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@be80be I've never seen one with four legs. Thanks for the education.

 

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If the three loads are similar then the neutral is not required. But if no neutral is provided then the three loads really need to be very close.

 

If you look at first post it's clear what the TS has he has a heater that has 3 elements all are tied to the neutral that let's you hook this up on any panel that has 3 open slots using smaller wire to get a much higher current flow say as been said 3 40 amp circuits this is very common on hot tub heaters
On demand heaters mat washers