[RE-wrenches] Heinz 57 off-grid array - Side discussion about mix-n-match

[Mick Abraham]

Hi, Wrenchies~

If code compliance were not an issue, one might connect a Photowatt 47 in
parallel with a Golden Genesis 75 to effectively yield a 122 watt unit
around 17 volts @ max power...and those two resulting units could then be
connected in series with the two Kyocera 120's to create a single charging
string around 68 volts & 7 amps. In a situation where the client doesn't
want to junk their Heinz 57 modules...that would work, wouldn't it?

Then the PW 1000 modules could be jumpered back to 24 volt nominal per each
and chain those into a second charging string, also around 68 volts @ the
max power point.

I realize Bob Clark may not want to go there for various reasons but this
exercise might prove useful in other situations. Replies would be
appreciated as part of my ongoing education.

Side note: Abandoning perfectly good but non UL modules seems of low
importance when the voltage is relatively low...because the "UL compliant
array combiner box" which would surely be installed has the overcurrent
devices necessary to protect against potentially bad events...and those
events are quite unlikely anyway.

Jolliness,

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675


On Sun, May 2, 2010 at 2:29 PM, Bob Clark <bclark at solar-wind.us> wrote:

>   Wrenches:
>
>
>
> We were called to assess the status of an off-grid system that is not the
> worst I have seen, but it comes close.
>
>
>
> I have some preliminary thoughts about system redesign, but would like to
> hear from the Wrenches about the array.
>
>
>
> *Givens:*
>
> We will not install anything unless it is to code.  It is obvious that none
> of the existing system was installed to code.
>
> We will use the existing 24V battery bank consisting of 8, Trojan L16s.
>  The batteries are still “relatively fresh.”
>
> Pump is a Franklin pump ½ hp 115VAC.  The CFs dim when the pump starts.
>
> New load will be a GRINDER PUMP FOR SEPTIC = 2HP, 15amp (240 or 120VAC –
> more than likely it will be 240V pump) – Another light dimmer!
>
> Modest daily electrical load (estimate no more than 600 WHr/day; 25AHr) –
> they are *very good* at managing their electrical use.
>
>
>
> *Solar array – to keep or replace?*
>
> 8 solar modules – a Heinz 57 mix of older modules - 2 Photowatt PMX500 (Are
> these modules UL listed?  There did not appear to be a rating label on the
> back.) wired in series, 2 Kyocera KC120-1 wired in series, 2 Golden Genesis
> PV-75 wired in series, 2 Photowatt PW 1000 12V-24V internally wired for 24V
> wired in parallel with the other modules strings – all of these modules are
> wired in 5 parallel strings for approximately 34.2Vmp and 20.4Imp, ~695W
> (STC).   Oh, and they need a new mounting structures for the modules.
>
>
>
> Should I try to work with these modules or advise the customer to start
> over (any modules that are not UL listed will have to go)?
>
>
>
> What is a good “rule of thumb” for a ratio of PV watts to battery bank
> capacity per day of autonomy?
>
>
>
> Thanks for your ideas.
>
>
>
> *Bob Clark*
>
> *SolarWind Energy Systems, LLC*
>
>
>
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