[RE-wrenches] Charge Control in AC coupled system

[Nathan Jones]

Wrenches,
We installed an AC coupled system a couple of years ago using a SB 3000 back feeding a Magnum MS 4448 AE. Array size is 2.4KW. The customer now wants to add a duplicate array with another SB 3000. From what I have read here on the 50% rule are we going to have shutdown/compatibility issues here if we back feed the Magnum with the second string? We can bypass it and feed the main panel instead of the sub but will lose the second array output in a power failure. Any help is appreciated.
Nathan Jones
Power Source Solar Inc.
417-827-0738



--- On Fri, 10/29/10, jay peltz <jay at asis.com> wrote:

From: jay peltz <jay at asis.com>
Subject: Re: [RE-wrenches] Charge Control in AC coupled system
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Friday, October 29, 2010, 12:11 PM

Hi Darryl,

Interesting you mention is 50% rule.
Is this true for all bi-directional inverters?
And curious how you found out?  hard way or via engineer?

thanks,

jay


On Oct 29, 2010, at 9:18 AM, Darryl Thayer wrote:

> The Morningstar relay driver can exercize an AC laod to take the heaver loads from the inverter by controlling AC loads as Jay mentions. 
> 
> BTW this works well but becareful to have the battery system inverter larger than the direct grid inverter otherwise the battery inverter will shut down the DG inverter when you go much beyond 50% of the battery inverter capacity.  
> 
> Darryl 
> 
> --- On Fri, 10/29/10, jay peltz <jay at asis.com> wrote:
> 
>> From: jay peltz <jay at asis.com>
>> Subject: Re: [RE-wrenches] Charge Control in AC coupled system
>> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>> Date: Friday, October 29, 2010, 10:49 AM
>> Don't forget that you can use a AC
>> load as well for an AC coupled system.
>> 
>> jay
>> peltz power
>> 
>> 
>> On Oct 28, 2010, at 8:25 PM, Kent Osterberg wrote:
>> 
>>> Howie,
>>> 
>>> In an ac coupled system with Outback inverters you
>> could use a diversion controller such as a Morningstar
>> Tristar 60 on the dc side.  That would allow using an
>> ac coupled system and a nicely controlled finish charge for
>> the batteries too.  Since there is already a MX60 to do
>> the finish charge in the system you are considering, a
>> voltage controlled switch, like the Morningstar relay
>> driver, could simply shut down the SB3000.
>>> 
>>> Kent Osterberg
>>> Blue Mountain Solar
>>> 
>>> 
>>> Howie Michaelson wrote:
>>>> Hi All,
>>>> 
>>>> I have done several AC coupled off-grid systems
>> using Sunny Islands and
>>>> Sunny Boys, but I am now doing one with a dual
>> stacked OB VFX3648 (with a
>>>> PSX240 on the Inverter out for load balancing) and
>> a SB3000.  There is
>>>> also an existing array that is running through an
>> MX60.  What I am
>>>> wondering about is how folks have set up AC
>> coupled string inverters to
>>>> best utilize the solar gain while not toasting the
>> batteries.  I'm a big
>>>> fan of the tapering control offered by SMA through
>> the frequency shift of
>>>> the SI's, but that's not available here. 
>> What relay/contactor setup have
>>>> folks found most efficient and safe?  Thanks
>> in advance,
>>>> 
>>>> Howie
>>>>   
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