proper inverter [RE-wrenches]

[Darryl Thayer]

Thanks Bill and William
The owner does not know the module brand, nor does any
of the paper work he has state.  The roof is high and
all I could reach was the bottom row. I could not see
any labels.  With out a better look I would be
guessing, (I think Kyocera).   I will rent either a 48
or 52' extension ladder and hope when I do the job.  I
think my best bet is to wire them into two sub arrays
of 325 Volts OC.  When it gets cold in MN this is up
north, I might see 400 Voc.  When it gets hot, ambient
+ 20C or 20% loss in voltage so Vmp will be about 250
volts in the summer.  

Bill mentiioned the Outback Combiner box, with just
two arrays could I not use a 600 volt fused
disconnect? then How would I find 10 or 12 amp fuses
in standard form? ( guess I will stick with the
Outback)

I do not know how the collectors got up there, but
there is almost no room underneath.  

For an inverter I am thinking the Fronius 4000. 
Anyone have experiance with this inverter?  I have a
3840 nameplate watts (I think) array at STC, but my
125% brightness and my 125% cold weather would I be
pushing it?  (My amps seem to be in range) (BTW I do
not feel confortable using manufacture's charts. 
Based on one experiance where the chart seems to be
wrong.)    

Thanks Darryl
> Darryl:
> 
> 
> This sounds like a tough situation.  What make/model
> are the modules?  Did 
> you try using on-line sizing tools provided by the
> inverter manufacturers 
> to get some string quantity options?
> 
> This brings out some philosophical points that were
> touched on recently in 
> this forum, at least peripherally:  Top down versus
> bottom up.  Top down, 
> to me, means the modules are mounted first on
> non-liftable rack and then 
> wired.  Bottom up is when the modules are mounted on
> a liftable rack and 
> wired from underneath.
> 
> The trend, of course, is top down and is made
> possible by the advent of MC 
> cables.  My unique position on MC cables is well
> known.
> 
> One additional disadvantage of top down is that it
> is difficult to 
> troubleshoot or modify wiring.  You state that the
> client wants a cheap 
> fix, but that may not be possible.  You did not
> perform the original 
> installation so you are not obligated to perform
> miracles on the 
> cheap.  Purusant to redesign, this array may need to
> be completely 
> disassembled and rewired.
> 
> Good luck and let us know how it works out.
> 
> William Miller
> 
> At 06:01 AM 3/19/2006, you wrote:
> >Hello
> >looking for some ideas or solutions.   Perhaps an
> >inverter recommendation.
> >I have a system not of my creation, that is
> composed
> >of 32  (12 volt) modules mounted tight to the
> standing
> >seam roof.  I have reason to believe the modules
> are
> >120 watt. Connections are under the modules
> arranged
> >in rows of 4 across and 8 rows high, tight
> together.
> >The connections on the end of each row are brought
> to
> >junction boxes and then 100 feet to the inverter
> >location.  The conduit is large.  The installer has
> >changed his expertise and left the area and no
> owner's
> >manual.
> >
> >My problem is they are connected in series and I
> >measured the open circuit voltage at over 648 volts
> on
> >a heavy overcast and cool day. .  My guess is on a
> >cold day this would exceed 720 Voc.  The owner
> wants
> >it fixed at low cost, just a new inverter and
> change
> >the wiring.  The roof is difficult to reach, being
> >high and at a 45 degree angle.  I can reach a
> splice
> >every 4 modules connected in series. Such that I
> can
> >create 84, 168, 336, 672 Voc by reconnecting into
> sub
> >arrays.  If my guess is correct the Vmp is 16.9 and
> my
> >sub arrays would be 68, 135, 270, 541 Vmp.     I
> have
> >worked mostly with Outbacks and Sunny Boys.  The
> 3840
> >watts seems to high for the Outback.  The voltage
> >range of 270 Vmp seems to low for the SB voltage
> >window when the modules get hot.  What
> >recommendations?
> >I know you that work with lots of inverters this
> seems
> >stupid.
> >Thanks you
> >Darryl
> >



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