[RE-wrenches] Main panel and ATS request

[Gary Willett]

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 at positiveenergysolar.com_ <mailto:Allan at 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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