[RE-wrenches] Convert Grid Tie SW4048 to Backup System; Add New Inverter, AC Coupled

[Nathan Jones]

If the SW4048 were being operated in an AC coupled arrangement it should be okay to pass AC coupled power through as it is UL1741 certified. The more stringent requirements for the line tied inverter would then fall to the GTI backfeeding it, at least as I understand things. I was under the impression UL1741 allowed incoming AC and disconnected upon interuption or frequency/voltage variations for islanding protection. The more stringent requirements for bi-directional interconnection required the "tugging" on the utility wave form to insure it was truly supplied by them. If this is correct then the SW should be capable of being used in an AC coupled arrangement just like a Magnum for instance. If this is not the case please correct me.
Nathan Jones
Power Source Solar
Springfield, MO
417-827-0738
On Sun, Nov 20, 2011 5:33 AM CST Kirk Herander wrote:

>PS - Richard, does it have a Trace / Xantrex GTI interface installed? If
>not, it's not code-legal to be tied to the grid anyway. Get rid of the 4048
>whatever you do.
>
>Kirk Herander
>VT Solar, LLC
>dba Vermont Solar Engineering
>NABCEPTM Certified installer Charter Member
>NYSERDA-eligible Installer
>VT RE Incentive Program Partner
>
>
>-----Original Message-----
>From: re-wrenches-bounces at lists.re-wrenches.org
>[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Richard L
>Ratico
>Sent: Friday, November 18, 2011 6:53 PM
>To: re-wrenches at lists.re-wrenches.org
>Subject: Re: [RE-wrenches] Convert Grid Tie SW4048 to Backup System; Add New
>Inverter, AC Coupled
>
>Jay, Marv, Chris, Ray, Joel & Maverick,
>
>Thanks tremendously for your input. Each of you provided interesting
>suggestions, all of which I find thought provoking and helpful. I greatly
>appreciate your taking the time to share your experience.
>
>Dick
>Solarwind Electric
>
>
>--- You wrote:
>We redid one in a very similar situation recently. In that case the 
>customer wanted super backup and so we put in Grid tie Outbacks and a 
>new battery bank, added modules, and kept the SWs as battery chargers 
>from the generator. He had the option with bypass switches to use the 
>SWs, if the Outbacks went out. This guy wanted a "keep the power going, 
>no matter what" system, but I can't claim that was optimal.  The right 
>answer depends on what the customer wants.
>I probably wouldn't trash everything though as Jay suggested, since the 
>existing modules are already racked and wired. (unless it's a bogus 
>install, then yep, salvage it all)
>You could probably easily rewire the parallel 48 v sets of modules all 
>in series in 15 minutes in the combiner box to get the voltage up, and 
>use a small GT only inverter, too. I guess it would also depend on how 
>close the 2 different types of modules are in voltage or current, but it 
>doesn't have to be perfect; as these were modules headed to the scrap 
>heap otherwise.
>In honor of modules that are well installed and still performing 
>correctly, I do try and reuse them. Being able to brag: "these have been 
>working for 30 years..." is great for the solar industry as a whole, but 
>only if it makes sense.
>
>Ray
>
>On 11/17/2011 5:51 PM, jay peltz wrote:
>> HI Richard,
>>
>> I'll chime in, although you won't like it.
>>
>> Dump the system and start over with a new battery less system and a genny
>as
>back up.
>>
>> Told you, you wouldn't like it.
>>
>> The SW parts are basically gone and it was a terrible  grid tied inverter
>anyway.
>> The modules are usable but why at $1.5 watt keep them?
>> Client doesn't want MX, so that means no batteries.
>>
>> You'll need a genny as back up anyway for long power outages during
>storms, so
>get a natural gas/propane unit as back up instead of batteries.
>>
>> OK you asked,
>>
>> jay
>>
>> peltz power
>> On Nov 17, 2011, at 4:03 PM, Richard L Ratico wrote:
>>
>>> Hi Wrenches,
>>>
>>> This is a repost. No replies the first time, so I'm trying one last time.
>>>
>>> I may be "adopting" an eleven year old, Y2K, grid tie with battery
>back-up
>>> system. It consists of 12 - Astro-Power 120 modules, installed in 2000,
>12 -
>>> Evergreen  EC-110 modules installed in 2004, only one MX60, which
>controls
>BOTH
>>> sub-arrays, one SW4048 in SELL mode through a dedicated load sub-panel.
>>> Existing, seven year old battery is shot (8-Trojan L-16). Initial bank of
>>> unknown batteries was replaced after only four years.
>>>
>>> Recent long, nearby, utility outages have the client requesting a
>proposal to
>>> include a new back-up generator and to restore the system selling to the
>grid.
>>> Client may decide go straight grid tie to eliminate the batteries. They
>have
>>> found the maintenance to be a hassle.
>>>
>>> My thoughts so far:
>>>
>>> 1)To take advantage of most of the existing hardware, I wonder if it
>makes
>sense
>>> to try to improve the system efficiency by relegating the SW to a manual
>back-up
>>> mode only, where, say, by means of a timer controlling grid availability
>through
>>> AC1, it would only charge a smaller battery bank once a week. The battery
>bank
>>> would be small,
>>> a single string of either, sealed gel units or T-105s with the new Trojan
>>> watering system.
>>> 2) Provide new grid-tie inverter/s (appropriate string type or Enphase
>190s)
>to
>>> handle the net metering.
>>> 3) Provide a way to AC couple the new inverter/s to the SW in the event
>of an
>>> outage.
>>> 4) Provide a new Honda 3000 inverter type generator connected to AC2 in
>the
>SW.
>>> 5)Provide a way to lockout the grid tie inverter/s when the generator is
>>> operating.
>>>
>>> Any thoughts or suggestions would be greatly appreciated.
>>>
>>> Thanks in advance,
>>>
>>> Dick Ratico
>>> Solarwind Electric
>>> Bradford, VT
>--- end of quote ---
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