[RE-wrenches] off-grid AC coupling feasibility

[drake.chamberlin at redwoodalliance.org]

Yes, we have a system with AC and DC coupled arrays on an off-grid
system. Having DC coupled capacity is important for reasons given in
other posts. 

We used AC coupling due to shade issues, so we could use Enphase
inverters. 

In your case, if the house really is going to go on grid, I would think
AC coupling makes sense. If not, I'd use high voltage DC charge
controllers (like the Schneider 600 V units) and keep it DC. 

The main complaint I have with AC coupling off grid is that some lights
tent to strobe in certain charging conditions. Another complaint  is the
5 minute delay period after the micro-inverters shut down. The micros
are phased, based on battery voltage, so they don't all shut down at
once. 

Drake Chamberlin 

Athens Electric LLC 

Ohio Electrical Contractor's License 44810 

CO Master Electrician's License 4526 

NABCEP Certified PV Installation Professional 

---

On 2022-07-30 12:30, Kirk Herander via RE-wrenches wrote:

> All, 
> Anyone out there successfully AC-coupled inverters in an off-grid system? Advantages vs. pitfalls? 
> 
> In my case I'm thinking of its practicality with a Solaredge inverter AC-coupled to an OB Radian inverter. OB firmware makes this pretty easy now. So effectively the Radian is always operating in a grid-backup mode. 
> 
> I already upgraded the system to the Radian, and soon to add 5kw of pole-mounted PV(currently only 1.8kw of 22-year old PV on the roof). This system also just got 16kwh of Blue Ion LFP batteries. 
> 
> This is a last-minute thought I have instead of investing in additional DC charge controllers for the new array. 
> Cost-wise there's not much of a difference between several high-quality charge controllers and a smaller SE inverter w/optimisers. Thanks.
> -- 
> 
> Kirk Herander / kirkh at vermont.solar 
> 
> Owner|Principal, VT Solar, LLC 
> 
> _Celebrating our 31st Anniversary 1991-2022!!_ 
> 
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> 
> dba Vermont Solar Engineering 
> 
> 802.863.1202 
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