Umm, just an FYI, I actually got dinged for labeling the AC output panel from a 
battery backup inverter as "Critical Loads".. Critical loads (Critical Branch 
circuits) are defined in article 100 of the NEC as circuits associated with 
Patient Care.. AC loads from battery backup inverters are more appropriately 
defined as "Dedicated Loads"..
Maybe someone could correct me here, but I'm under the impression most 
garden-variety inverters are not rated for Critical Load applications.
db
________________________________
From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> on behalf of 
William Miller via RE-wrenches <re-wrenches@lists.re-wrenches.org>
Sent: Saturday, August 9, 2025 1:03 PM
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Cc: William Miller <will...@millersolar.com>
Subject: Re: [RE-wrenches] Adding battery to grid tie

Correct me if I'm wrong:  I believe AIOs can accept AC coupled power through 
the load ‘output’ port. That leaves the Grid and Gen inputs free for their 
roles as labelled.

The AC coupled inverters connect via a breaker in the critical loads panel.


William Miller
Miller Solar.com
805-438-5600
www.millersolar.com<http://www.millersolar.com>


On Sat, Aug 9, 2025 at 9:50 AM david quattro via RE-wrenches 
<re-wrenches@lists.re-wrenches.org<mailto:re-wrenches@lists.re-wrenches.org>> 
wrote:
True.  if you want to do grid, gen, and AC Couple then you need a transfer 
switch or contactor.
       Likewise I haven’t touched a Powerwall, nor an Enphase battery.



On Sat, Aug 9, 2025 at 9:36 AM jay via RE-wrenches 
<re-wrenches@lists.re-wrenches.org<mailto:re-wrenches@lists.re-wrenches.org>> 
wrote:
One big issue with the AIO’s is that you can’t do grid, generator and ac 
coupling to the best of my understanding

I do like the idea of just removing the old GT inverter and stuffing that into 
the AIO, elegant

yes its my understanding that Tesla won’t accept generator.  While many are 
pissed off at eg4, I won’t touch tesla.

and FYI you can buy the same inverter at Fortress.

thanks everyone.

jay



On Aug 9, 2025, at 10:28 AM, Tyrone Houck via RE-wrenches 
<re-wrenches@lists.re-wrenches.org<mailto:re-wrenches@lists.re-wrenches.org>> 
wrote:

Midnite AIO and Sol-Ark both work great for AC coupling in my experience. If 
anyone is new to "All In One" inverters I recommend having tech support walk 
you through commissioning, check firmware, etc. the first time.




On Sat, Aug 9, 2025, 8:47 AM William Miller via RE-wrenches 
<re-wrenches@lists.re-wrenches.org<mailto:re-wrenches@lists.re-wrenches.org>> 
wrote:
Two options:

1. AC couple existing inverter to a battery capable inverter.

2. Replace existing inverter.

I favor option 2.

Option 1 is only preferred if gaining access to the existing inverter for 
replacement is difficult. An example would be a micro-inverter system.

New AIO inverters allow true high voltage PV input so the existing stringing 
will probably not need to be modified.

I’m new to this so type of upgrade so I welcome any corrections to these 
opinions.  I did replace a Sunny Boy in my shop with a Soul Ark and it’s 
working great!

William Miller
Miller Solar.com
805-438-5600
www.millersolar.com<http://www.millersolar.com/>


On Sat, Aug 9, 2025 at 8:26 AM Jay via RE-wrenches 
<re-wrenches@lists.re-wrenches.org<mailto:re-wrenches@lists.re-wrenches.org>> 
wrote:
Is there a consensus as to what equipment to use for adding battery backup to 
normal GT inverter?



I’ve had a few people ask and I actually haven’t done it.

Thx
Jay


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