[RE-wrenches] NEC 690.10(C) talking points

[Dave Click]

Dan,

690.10(C) doesn't say no. It says that if you have a single 120V 
inverter output connected directly for a 120/240 panel then you can't 
put a 240V load in the panel-- in this case you'd either have L 
connected to both phases of the panel or I guess you could just use half 
the breakers in the panel. For a 240V load it would just see 0 volts 
phase to phase, but for a multi-wire branch circuit with current on both 
legs you'd potentially overload your neutral conductor.

Now when you use either a 240V inverter (or two stacked 120s) or an 
autotransformer between the inverter and the panel, 240V loads are fine 
since you have two lines 180 degrees out of phase and voila, 240V. 
690.10(C) wouldn't apply to this situation since your inverter(s) would 
be supplying 240V (not 120) to your 1P 3W panel.

DKC

On 2014/3/19, 20:40, Dan Fink wrote:
> Esteemed Wrenches;
> Can anyone here help me with some simple talking points for clients 
> installing off grid systems? 240 Well pumps hard wired to panel 
> breakers are common, but everybody (who has even a chance of surviving 
> up here in middle of nowhere way off grid) NEEDS a 240v welder outlet 
> in the garage/workshop. But 690.10(C) says no.
>
> Am I missing something obvious? What do I tell these potential clients?
>
> Dan Fink,
> Executive Director;
> Otherpower
> Buckville Energy Consulting
> Buckville Publications LLC
> NABCEP / IREC accredited Continuing Education Providers
> 970.672.4342
>
>
>
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