Placement of Automatic Transfer Switch for Grid-Tied Battery Back up System

midijeep

I would like to place a generator with an ATS on my Grid-Tied Battery Back up System.  I have an Eaton EGSU100ACA ATS.  I made a outline of my system (see pdf file).  I wanted to get advice on the placement of the ATS.  The most logical place that comes to mind is the AC line coming from the outside main utility panel to the midnite solar E-panel.  Would this be appropriate placement?

mcgivor

What is in place to prevent the GT inverter from trying to feed into the generator?

BB.

The Sunny Island has a grid/genset input and a sense input (on=genset available, off=no genset available).

I would suggest that you connect your AC input to the SunnyIsland and use the genset selector. This lets the SI change the AC input characteristics between Grid and Genset:

http://files.sma.de/dl/5610/TechNDIGIN-HUS123112.pdf

I have not looked in detail at the SunnyIsland--Go through the installation manual and any support documents you can find.

A question--The SunnyIsland is going to run protected loads. Is the genset only going to power the protected loads panel, or will you have other loads that may run from only the grid/genset (i.e., electric drier, large shop tools, etc.). Among your genset ATS choices--Whole house, two protected panels (genset and genset+SunnyIsland), or only one protected (SunnyIsland only).

Since you are looking at a SunnyBoy for GT solar--That should be compatible with the SunnyIsland and connected to the AC Output of the SI (protected load panel). The SI will vary line frequency a little bit to modulate the SMA GT Inverter(s) as needed (battery charging+loads). I believe the SI AC input will isolate the genset when SI is in genset mode.

-Bill

midijeep

mcgivor said:

What is in place to prevent the GT inverter from trying to feed into the generator?

The SMA Sunny Island prevents that by knowing if it is connected to the grid or not via 120v external auxiliary relay. The relay needs to be connect to the AC side of the ATS.

midijeep

BB. said:

A question--The SunnyIsland is going to run protected loads. Is the genset only going to power the protected loads panel, or will you have other loads that may run from only the grid/genset (i.e., electric drier, large shop tools, etc.). Among your genset ATS choices--Whole house, two protected panels (genset and genset+SunnyIsland), or only one protected (SunnyIsland only).



-Bill

I mainly want to be able to recharge the battery bank if for some reason the PV can't.  When the grid goes off line the PV and generator will work in tandem if needed.   I have enough  battery capacity to run for 3 days without PV.  The SI branches off to an essentials panel, so not the entire home will need to be powered.

midijeep

BB. said:

The Sunny Island has a grid/genset input and a sense input (on=genset available, off=no genset available).

I would suggest that you connect your AC input to the SunnyIsland and use the genset selector. This lets the SI change the AC input characteristics between Grid and Genset:

http://files.sma.de/dl/5610/TechNDIGIN-HUS123112.pdf

Since you are looking at a SunnyBoy for GT solar--That should be compatible with the SunnyIsland and connected to the AC Output of the SI (protected load panel). The SI will vary line frequency a little bit to modulate the SMA GT Inverter(s) as needed (battery charging+loads). I believe the SI AC input will isolate the genset when SI is in genset mode.

-Bill

I have the AC input going to the Midnite Solar E-panel, the SunnyBoy goes to the E-Panel, then come out of the E-panel goes to the AC2 of the SI. The SI decides what it will do with the power i.e send it to the loads, charge the battery bank , ect... ....
 My question is can I place the ATS between the Main Panel (AC input )and the E-Panel  The E-panel already has the AC input going into it now, I just want to put it between the Main Break panel and E-panel and let the SI use its Relay to know if it is on the grid or not.  I think the ATS will automatically switch to the Gen once the grid goes down and then the SI will start to look for wider frequency from the generator.
Will me placing the ATS between the AC inout and E-Panel work?

mcgivor

As long as you are confident everything on your site of the ATS will function as described, that would be a logical place for the ATS, the grid side and load side should have no physical connection of any sort, to prevent back feeding the grid. Please note I'm not familiar with SI equipment, just stressing the importance of isolation from the grid, whilst the generator is running.

BB.

I do not believe that is how the SI is designed (genset+ATS on AC1--protected load output). (Note that, it appears, that A1 is the protected sided of a SI, and A2 is the genset side--sort of backwards from US convention).

You generally need to put the grid+genset+ATS on the AC2 (grid/genset input) side of the SI.

Now--It does depend on how the particular E-Panel is wired... There can be an AC bypass switch setup that disconnects the SI from input/output AC loads and instead connects the Grid+genset+ATS directly to the protected AC loads. This is done for service and to allow you to bypass a failed SI (if that ever happens to you).

Anyway, here is a planning guide for the SI system... See if this helps you. I am not a consultant, and I can only give you general guidelines and suggestions. All installations need to comply with the product(s) manual(s) and your local code.

http://files.sma.de/dl/1353/Designing-OffGridSystem-PL-en-22.pdf (planning guide for SunnyIsland systems)

This is not a small/simple system to design/install/configure. Are you planning on using an experienced installer for this system?

-Bill