[RE-wrenches] 208 3 phase Off Grid Inverter

Tue Mar 25 21:37:21 PDT 2014

Thanks Kevin;

I follow what you are saying on the charge algorithm:  both the inverter 
and charge controller are very smart, but aren't talking to each other, 
which makes for a dysfunctional family with the batteries being the 
neglected kids.  In this case, I could see that a full on SMA solution 
would work nicely: Sunny boys AC coupled, SIs hooked up with the 
Multicluster box, etc.
I yearn for those good, old days, when I could  build dream systems, 
while charging full retail.  Lately, I work twice as hard just to build 
systems that will still work on much tighter budgets.
I'll hit up the folks at SMA, as I think that SIs will be in the mix in 
some fashion.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 3/25/2014 10:08 PM, Kevin Pegg wrote:
> Hi Ray,
>
> Suggest you give the techs a call @ SMA and get some design assistance. They are good.
>
> Sunny Islands can be used as regular inverter/charger units yes.
>
> >From my experience, we have done 1 string of 3 SI inverters (ie 18 kW @ 120/208) without the multicluster box. Anything larger than 1 string we have always used the MC box. I believe it's required - or at least the control board that handles communication between inverters is required. The MC cabinet is very nicely done and makes inspectors very happy this is for sure.
>
> As far as DC input from charge controller ie Classic yes this is also possible. Screws up the inverter's very smart battery charge algorithm, however. So there is a trade-off there. It will depend how much this site is relying on diesel vs PV input.
>
> Kevin
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org]On Behalf Of Ray
> Walters
> Sent: March 25, 2014 4:37 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] 208 3 phase Off Grid Inverter
>
>
> OK everyone is steering me towards the Sunny Island.   I can probably
> justify the inverter cost difference to the customer, then I found the
> SMA Multicluster Box for the SI.  It seems like a glorified AC Combiner
> and transfer switch box, but it retails for over $20K! Yikes.
> Do we have to use that for a 3 phase install, or are there much lower
> cost alternatives.  This is out of the country and does not need to be
> NEC2014 compliant.  (maybe NEC 1956 compliant would be about in keeping
> with the rest of the wiring.......)  This would be a budget buster for
> sure.
>
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer,
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
>
> On 3/25/2014 4:21 PM, Kevin Pegg wrote:
>> Hi Ray,
>>
>> I have several 3-phase off-grid inverter/battery/generator systems out there.
>>
>> - SMA Sunny Island is the best. Can scale to at least 180 kW, maybe more. Reliable & very solid. I have several sites going over 2 years without a single second of power outage.
>> - Xantrex XW. It can work in a 3-ph config, but it's not as stable system. We have taken to preventatively rebooting the systems every 4 months and that helps a lot - at least the outage can be planned and on our terms.
>> - Outback has had so many power quality nightmares I won't go there anymore.
>> - I believe Magnum has a 3-ph option but haven't installed one yet.
>>
>> SMA inverters are more expensive. And they work very well. They also have a very good battery charging algorithm and integral gen start control.
>>
>> Kevin
>>
>> -----Original Message-----
>> From: re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org]On Behalf Of Ray
>> Walters
>> Sent: March 24, 2014 6:44 PM
>> To: RE-wrenches
>> Subject: [RE-wrenches] 208 3 phase Off Grid Inverter
>>
>>
>> Hi All;
>>
>> I'm exploring options for an off grid project with an existing 30 Kw
>> Kohler wired for 208 vac 3 phase.  The generator runs some 8 hp air
>> compressors, so rewiring it is not an option.  We're primarily
>> interested in reducing gen run time from the current situation: 14 hrs/ day.
>> So far, only the Outback VFX inverters seem capable of being wired in
>> 208, 3 phase, but according to the manual they can only be stacked 1
>> inverter per leg. This limits the system to only 3 inverters total, or
>> 10.8 kW.  I would like expandability beyond this.
>> 1) are there any other inverters available that I'm over looking?
>> 2) Should I consider a transformer to convert from 208 vac/3phase to 240
>> vac/ singe phase?
>>
>> We're not going to even try to run the compressors, just the other
>> single phase loads, mostly 120 vac, but we have a couple of small air
>> conditioners, that are currently running on 208 single phase.  I believe
>> they would run fine on 240 vac, as they have a name plate rating at 230 vac.
>> 3) We may possibly run 2 separate 3 inverter stacks and only tie
>> together at the battery, but otherwise they would not be connected. This
>> seems inefficient, and would require some load balancing of the various
>> inverters.
>>
>> All help and discussion is greatly appreciated as always,
>>
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