[RE-wrenches] Heinz 57 off-grid array - What should I do with the solar modules?

[R Ray Walters]

HI Bob;

I've done a bunch of that rewire stuff. Reusing the modules? I would, if they were on a decent mount. 
Since a) they're not on a good mount, and 
b) none of those are top shelf panels, 
I'd probably trade them in or have the customer resell them. Many folks just starting out could use those modules on 12 v systems.
I can say I've reracked mixed arrays like that, rewired everything, worked very hard, and then, when it was all over, I was kind of embarrassed at the final result. (both looks and performance)
You might save a bit of money on PV, but all the labor is going to be ridiculous. It will take longer to "customize" a new rack and deal with all the different types of wiring, than just install a new rack with fresh modules, and an MPPT controller. Cost more? yea, but when you go back in 5 years both you and the customer will be happier. I promise.
Jurisdictions vary, but you're usually required just to meet the requirements of the code that was in place, when the original work was done, not the latest NEC version; so that gives you a bit more latitude.
Also, in situations like that, I start looking at other options: supply parts and advice, and let them do some of the work, pass it to an employee as a side job, so it's not on your watch,
etc. 
We wrenches just can't fix every system on the planet; at least not in one life time.

Good Luck, 

R. Walters
ray at solarray.com
Solar Engineer




On May 2, 2010, at 2:29 PM, Bob Clark 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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