I have a small grid-connected solar PV system. If it is connected to my main load center via a two-pole breaker, how can I safely add a generator inlet to this system ?
The usual method is to connect a generator is via a NEMA 14-30 jack, which is connected to the load center via a two-pole breaker. An interlock prevents this two-pole breaker from being turned on until the main breaker is first turned off; this prevents backfeeding the grid from the generator and endangering line workers. (Some jurisdictions do not allow a simple interlock, but rather a separate transfer switch, for which case my dilemma would not exist).
If the grid-tied solar inverter (GTI) is connected via another breaker, then, since there is no mechanism I know of which can interlock the main breaker with TWO branch-circuit breakers, it would be possible to have both the generator and the GTI connected to the load center simultaneously. This seems problematic. But, is this actually safe, because the GTI's U1741 capability might prevent it from being activated, since it wouldn't detect the generator's output as being up to grid spec) ?
This is all moot if one connects the GTI to the line side of the main breakers (using insulation-displacement connectors such as those made by Buchanan). But even though I've done this, it seems un-wholesome, given that the wiring between the panel and the GTI (not to mention the inverter itself) is not protected by ANY over-current protection device (OCPD), notwithstanding what exists at the power-company's transformer.
Perhaps the only good solution is a transfer switch, or an essential-loads sub-panel, or one of the "generator ready" load centers, which is effectively an essential-loads sub-panel built into the same enclosure.