[RE-wrenches] Whole house backup

[Mac Lewis]

Hello Wrenches,

I'm working on a design and could use some other points of view.  I have a
potential client that would like some backup power.  His house is bored
into a sandstone cliff and would be exceedingly costly to get any conduit
in and out of the structure, so I'm trying to avoid it.  It's not possible
to consolidate a critical load panel.  He currently has a grid-tied system
mounted on poles out by his pedestal-mounted main service panel.  He has
large electric loads, 2 electric hot water heaters, an electric stove and
some very ancient refrigerators.  He may swap some of these out, but its
not possible to get gas lines to serve these large heat loads.  For the
backup part of his system, he doesn't need to run these large electrical
loads and he does not need the system to automatically switch over to
backup mode.  He is willing to throw a switch or two.
Here is my initial idea.
1. Put the whole house on a 200A manual transfer switch.
2. Backfeed (ie from AC input terminals on hybrid inverter), the main
service panel
3. Put the grid on one pole of the transfer switch, and connect the AC
output of the hybrid inverter to the other pole of the transfer switch.
4.  In order to keep the hybrid inverter from backfeeding itself, I'd put a
power relay that disconnects the AC input terminal of the hybrid inverter
from the main service panel when the grid is down, and keeps it locked out.
5.  Because this system would be a manual transfer, the owner could turn
off all of his large electric loads before he switched to backup mode.

It seems like it may work.

Thanks in advance for any feedback, or other design possibilities.




-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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