Re: leviton vizia RF switches (Z-wave)

["Robert L Bass" <no-sales-spam@bassburglaralarms>]

>> Physics and the US and Canadian electrical codes dictate that one
>> shouldn't move loads around willy-nilly in the AC power distribution
>> panel, but in my case, I could make significant improvements taking care
>> to keep the loads balanced and compliant with the NEC.
>
> While I agree that it is a good idea to balance loads across both phases, I couldn't find anything in the NEC regarding that
> issue...

NEC 70 mentions the subject in relation to neutral conductor size requirements.  The concern is that an unbalanced load can create
higher current on the neutral and (in the event of a break) on the grounding conductor.

  I may have missed
> it.  Except for some slight variation in voltage due to line drop in the neutral, the only component in the distribution network
> that might be effected by load balancing is the utility step-down transformer.

If the neutral opens any unbalanced load goes directly to the ground which might not be of sufficient gauge to handle it.  This
could lead to overheating and possibly fire.

> All three feeds to our main distribution panel are the same size, so the neutral is properly sized to handle the maximum current
> from either phase. That is not always the case, particularly in older buildings.

I don't know the physics well enough to be certain but presumably that's enough.

> Our major loads are the 240V A/C compressors necessary for this climate with peak summer temperatures well up in the teens.
> Lighting and convenience circuits are almost all on one phase, and the other phase supplies most electronics, fixed appliances,
> and other non-X10 circuits.  The XTB-II is just driving the X10 phase.  This configuration works very well.

We installed a 440/208 WYE transformer in my church some years ago.  The chief electrician did careful load calcs to make certain
the neutrals and grounding conductors wouldn't be overloaded.  Some time later the system got rewired to accommodate 40 or 50 new
1KW circuits.  It took a lot of time getting it straight again.  To date the place hasn't burned down so I guess we did it right.
:^)

--

Regards,
Robert L Bass

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