Allen:
I asked you about a generator since the future addition on one might
influence your selected solution.
The GenReady ATS does not include any load-shedding control algorithm
based on AC input voltage (representing full load/overload sensing) that
would have to be left unused.
The ATS "sensing breaker" and the "XFER", "BAT+, and "BAT-" leads are
intended to be used by a generator's controller board to sense a grid
brownout, overvoltage, or failure condition, apply its internal timing
algorithms, then activate the ATS. There are no "smarts" in the GenReady
panel's ATS - it's a "dumb" switch.
I have a Generac EcoGen propane generator with a 2-wire start, and no
internal controller. It has no internal "smarts" and relies totally on
the controller functionality internal to the PV inverter.
I'm using the Generac GenReady panel at my home installation as follows
for backing up critical loads:
(A) The inverter output from my XW system feeds the "Generator Supply"
breaker on GenReady panel.
(B) The AC1 grid connection on the XW is connected to the lowest 2-pole
breaker position on the top portion (non-protected) side of the GenReady
panel.
(C) The EcoGen generator is connected to the AC2 (generator) input on
the XW.
(D) In the "normal" configuration (no grid failure), the GenReady
internal ATS (automatic transfer switch) is already activated, and the
XW inverter's output is feeding local protected loads. XW PV production
in excess of local load and battery charging requirements is connected
to the upper portion of the GenReady panel, and is consumed by the local
non-protected loads, or sold back to the grid.
(E) With a grid failure, the GenReady ATS position does not change, and
the inverter continues to feed the protected loads (non-protected loads
are "dead"). The XW inverter will start/stop the generator as needed to
keep the batteries charged.
(F) So what is the GenReady ATS used for? It is not needed with a
dedicated protected loads panel, but provided two advantages in my
situation:
(1) I needed to upgrade my main service panel anyway, so choosing a
panel with an internal ATS made sense. Plus, I could connect a
generator for the protected loads (non-PV solution).
(2) With a PV solution, I use the GenReady ATS to manually bypass
the inverter. It's easier to do that to flip the four breakers in
the Xantrex AC Interconnection Panel. I haven't done this yet, but
it should be possible to have the XW inverter control the ATS to
switch the protected loads back to the inverter if a grid outage
occurs while the ATS is in the inverter bypass mode.
I totally agree with you that having an option to provide a critical
loads battery backup for solar installations is an underserved market,
particularly in rural areas with frequent grid outages and brownouts.
An integrated inverter/charger, in conjunction with a natural gas and/or
propane generator, feeding a separate critical loads panel is a great
solution to offer customers desiring an "UPS-like" configuration for
critical loads. The battery bank sizing will be a cost tradeoff between
hours of autonomy of the battery bank, versus size/run-time for the
generator (if equipped).
Hope this helps!
Regards,
Gary Willett, PE
Icarus Engineering / Solar Services LLC
NABCEP Certified Solar PV Installer # 031310-246
On 5/14/2011 4:28 PM, Allan Sindelar wrote:
Gary,
Thank you for the referral to this product; I didn't know it existed.
If you reread my original post, you'll see that there's no generator
involved; this is purely inverter- and battery-based. At the link you
provided, I was able to download a spec sheet, but the spec sheet
lacked some of the information to determine how well this would work
in an inverter-based situation. It appears that this unit includes a
load-shedding control algorithm based on AC input voltage
(representing full load/overload sensing) that would have to be left
unused. It's not clear to me that this could be set up to work as
simply as a shift-to-backup on the critical loads section could be
automatic and based solely on loss of grid AC. Have you used this in a
GTWB installation? ?If so, what can you tell us?
This unit retails around $350 and is based on a generator-based
application. I would think that a simple series of AC critical load
panels, that include a simple 30 or 60A 120/240 automatic transfer
switch function in order to switch critical loads from utility source
to inverter source, would be a product with a ready, small but growing
market. We have requests for sophisticated grid-tie with backup
systems, intended as preparation for possible permanent loss of
utility electricity.
Allan
*Allan Sindelar*
_Allan@positiveenergysolar.com_ <mailto:al...@positiveenergysolar.com>
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
*Positive Energy, Inc.*
3201 Calle Marie
Santa Fe, New Mexico 87507
*505 424-1112*
_www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
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