[RE-wrenches] 208 3 phase Off Grid Inverter

[Kevin Pegg]

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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