Solar panels on/off

Discussion in 'General Electronics Chat' started by BocasOne, Aug 12, 2014.

  1. BocasOne

    Thread Starter New Member

    Aug 12, 2014
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    I'm wondering if it is possible to use ordinary light switches to act as on/off switches for solar panels. They would be placed before the charge controller so that the incoming current could be switched off when hardware on the other side required work. Please note that where I'm located there are NO regulations so I can do whatever physically works for me. :D

    The panels will be wired 2-in-series and the following are the specs per panel:
    Max power: 124 W
    Voltage at Pmax: 30.0 V
    Current at Pmax: 4.13 A
    Short-circuit Current: 5.1 A
    Open-circuit Voltage: 42.0 V
    Max series fuse rating: 8 A
    Thanks.
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If by 'ordinary light switch' you mean one intended for switching domestic AC mains-voltage lights then the answer is no :(. The switch contacts are not rated for DC currents of several Amps and would soon be damaged by arcing.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Oh well then go right ahead and expose yourself to possible dangers that those regulations are intended to protect you from.. :rolleyes:

    Unless the switches are rated to be used with that application/voltage/current,etc... then they should NOT be used.
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Then please tell us what an acceptable mean-time-between-failures for each component in your system. In other words, I agree that regulations are just a way of promoting big government. Some little AC switches will work fine for a few dozen actuations.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    The "Code," or National Electrical Code, as used my many jurisdictions, is written entirely by the National Fire Protection Association (NFPA), which is a private organization. It is so thorough that is is accepted as written as the legal “code” by governing bodies.

    Note the author has FIRE PROTECTION right in the name. Typically not letting s building catch fire is a desirable thing.

    Using a switch not rated for what you are doing is playing Russian roulette.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Sorry, I didn't realize I forgot the sarcasm tag on my statement about big government.
     
  7. NorthGuy

    Active Member

    Jun 28, 2014
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    You can always disconnect the MC4 connector on the panel side (just don't do that under the load!!!) or between panels. This may not be very convenient, but it's very unlikely you ever need to disconnect it.
     
  8. profbuxton

    Member

    Feb 21, 2014
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    What wrong with covering the panels with a blanket? Or working at night?
    Although I would not use a switch rated for AC on DC if there is any load involved.
     
  9. BocasOne

    Thread Starter New Member

    Aug 12, 2014
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    That's what I wanted to know.... thanks, Gopher. I should try to make it clearer as to my "no regulations" where I live statement. People who live in a regulated society where inspections are required to meet building codes, fire codes, etc., think in terms of what is necessary to meet those regulations - I get that. I believe that most of those regulations are in place to protect the insurance industry or the device manufacturers against law suits, but if you have to have insurance, you have to follow the rules. While I don't wish to burn down my house, or die of electrocution, I should say that I am responsible for my own actions and as such, I'm self-insured. I really wasn't trying to start a philosophical discussion on whether or not the government should be protecting us from ourselves. I simply wanted to know whether or not connecting 2 wires together with a simple light switch would function without blowing up, starting a fire, or melting the switch.

    Sometimes, because of being in a remote location, you need to cobble some stuff together to make it work until you can buy what you actually need for the longer term. I know what I need - but right now, I have light switches.
     
  10. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Instead of a switch, couldn't you just pull the fuse on the rare occasion you need to disconnect the panels? You might need to attach shielding to protect from any arcing at the fuse-holder.
     
  11. ErnieM

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    Apr 24, 2011
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    But once again you need a fuse (and a fuse holder too) with a DC rating.
     
  12. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    And the fuse holder must be approved as a "fused disconnect" and not just a fuse holder :)
     
  13. mcgyvr

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    The answer is no.. It will not last long when used as a DC disconnect.
     
  14. ErnieM

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    Apr 24, 2011
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    The Square D companies line of QO breakers and panels do have a DC rating, and the breakers are rated for switch duty.
     
  15. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    You could use two switches in parallel. One wired normally and one having a 10 ohm or thereabouts high wattage resistor in series. The harsh arcing would be prevented at switch off by the higher resistance parallel path. Then that switch could be turned off, and again, harsh arcing would be greatly reduced by the resistance. Not a perfect solution, but it is cheap and would extend the life of the switches.

    Having said that, I would think someone with such expensive panels and associated equipment would WANT to spend just a little more for a properly sized and rated disconnect. Just good common sense I would think.
     
  16. NorthGuy

    Active Member

    Jun 28, 2014
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    True. Depending on the construction of the switch, 8A and 70V might be enough to start an arc. It may melt the contacts together, so that it doesn't disconnect at all, or the distance between disconnected contacts may be too short, so the arc will persist, continue conducting and melt the switch. It is impossible to predict whether any of this may happen or not because the switch hasn't been tested with DC. It is guaranteed not to happen with DC switch.
     
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