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re: no batteries -net metering
1 oct 2002
harry conover  wrote:

>"steve spence"  wrote: 

>> ...other states don't require that charge. only that there is a
>> outside disconnect, and a ul listed grid tie inverter.

some don't require an outside disconnect.

>doesn't this conflict with the national electrical code requirements?

no, the last time i looked.
>i don't have a copy handy right now, but i'm reasonably sure that it
>requires an approved switch be employed to select between grid power
>and home generated power to prevent back-feed to the power grid for
>the safety of power company linemen.

intelligen used an ordinary circuit breaker in the ordinary load center.

>there is no technical reason why a synchronous inverter could not be
>designed to be fail-safe, although i'm not aware of any that are.

the trace microsine comes to mind.

>the problem being that the current design of synchronous inverters are not
>fail-safe (nothing prevents them from going into self-excitation modes
>when connected to highly reactive loads)...

i think that's a matter of probability addressed by an ieee standard.

>and none that i am aware of are equipped with fail-safe disconnect relays
>(which generally command a price of over $1,000 -- with silver on graphite
>contacts, gravity driven fall-out, and tamper-proof enclosures).

an extra scr in series might help meet the spec. it seems to me the harder
problem is recognizing when grid power disappears, but there are lots of
good inexpensive ways to do that, eg comparing an fft to a template... :-)

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