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Gadget Freak Case #200: The Sun Lights Up the Deck at Night

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Rob Spiegel
User Rank
Blogger
Re: BOM costs
Rob Spiegel   1/26/2012 2:31:07 PM
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Good point, Chuck. Yes, the bill of materials here is not expensive. We're seeing this frequently with Gadget Freaks. Inventors are taking a few household items mixed with some inexpensive components and coming up with interesting gadgets.

WhEEngineer
User Rank
Gold
Re: Fire hazard?
WhEEngineer   12/27/2011 10:28:32 AM
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Just found NEC book, article 690 covers PV, it applies even if not backfed into the utility system.  Also, 690.4 states 'only qualified persons will be allowed to perform the described work on pv systems'.  690.4(e) Wiring and connections.  The equipment and systems in 690.4(A) through (D) and ALL ASSOCIATED WIRING AND OTHERCONNECTIONS shall be installed only by qualified persons.

Article 100: Qualified Person. A person who has the skill and knowledge related to the construction and operation of the electrical equipment and its installation. This person must have received safety training on the hazards involved with electrical systems.

As you know, PV works in 3 states:

1. open circuit where there is no current flow and voltage can reach 600v potential

2. short circuit where there is no voltage and currents flow without damaging the pv.

3. in a circuit, where the voltage and current are proportional to the applied load.

When a pv output is opened they act like a CT. where the interrupted current is being pushed by the pv, many times drawing an arc while the voltage rises to open circuit voltage.  This can be fixed by a shunting device, but I didn't notice one in the circuit.

Like I said, it works as designed but if it causes a fire will the insurance company pay the claim?  12 volts will burn down a house just like 120v.

One question to you as a PE, would you ceritify this installation to the inspectors and insurance industry as 'safe' if you had to put your PE license on the line?


Jack Rupert, PE
User Rank
Platinum
Re: Fire hazard?
Jack Rupert, PE   12/23/2011 3:12:31 PM
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WhEEngineer - Not sure what the NEC or the local inspectors might have to say about the details, but from how I read the article, the solar panel setup just feeds some 12VDC auxiliary lighting.  If he fed that into the house voltage it would provide a whole lot of light for about one second and then the LED's would be no more.

WhEEngineer
User Rank
Gold
Fire hazard?
WhEEngineer   12/15/2011 4:22:33 PM
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The wiring is not to NEC code and I hope this isn't being backfed into the house voltage, and I didn't notice an isolator for the solar panel and an inverter.  This is a great idea and works but the execution leaves a lot to be desired.  Don't let an inspector or insurance agent see this setup.

Charles Murray
User Rank
Blogger
Re: Strong spirit of supporting green environment
Charles Murray   12/13/2011 11:45:28 PM
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I agree, proent. The strength of this entry is the get-it-done spirit. There surely could have been more costly ways to accomplish it, but this designer was determined to make the garage sale items work, and he did it in impressive fashion.

proent
User Rank
Iron
Strong spirit of supporting green environment
proent   12/13/2011 6:51:51 PM
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Though the result is not that effective aganst being spent much effort, time, material cost especially the wiring is pretty wirings ! Anyway I admire the strong sense of make it done spirit, I am pretty admired and respected the idea.

missnoitall
User Rank
Iron
Nice project but...
missnoitall   12/13/2011 9:47:47 AM
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agree with earlier post.  If I could find a free or low cost solar panel, I would build this, or a similar system.  Without that, I would 'reverse' the main power source with the backup mains power source and just run off of AC with a backup battery and no solar!  This approach would meet all functional requirements except social acceptability.

Charles Murray
User Rank
Blogger
BOM costs
Charles Murray   12/12/2011 9:53:51 PM
Sounds like the real advantage to this system lies in the bill of materials. Buying the solar panel and regulator at a garage sale, the entire project must have cost almost nothing.

Alexander Wolfe
User Rank
Blogger
Re: What were the mods?
Alexander Wolfe   12/12/2011 3:09:31 PM
Watching the video, I was fearing for Mr. Grill's health-- he sounded decidedly winded. Also, this isn't so much a standalone gadget as it is an installation project. Nevertheless, I'd have to say he put together something worthy and interesting.

Ann R. Thryft
User Rank
Blogger
What were the mods?
Ann R. Thryft   12/12/2011 12:30:18 PM

What a great idea, and kills the proverbial two birds with one stone. My question: the caption for the second photo says "The LED based light modules were modified to maintain their sealed weather proofing." What was done to modify them for this purpose?


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