Why register? ...To Enhance Your Experience
+ Reply to Thread
Page 2 of 3 FirstFirst 123 LastLast
Results 21 to 40 of 48
  1. #21
    Forum Member
    Join Date
    Mar 2007
    Location
    Jacksonville Fl
    Posts
    507

    Default

    Quote Originally Posted by ScareCrow57 View Post
    OK. Basic electricity here. It is impossible to have 600 volts of DC current.
    Holy old thread batman!

    However... I think the guys that work on the NYC subway would beg to differ


  2. #22
    Forum Member
    Join Date
    Jan 2007
    Posts
    2,802

    Default

    Quote Originally Posted by FlyingKiwi View Post
    It is not 100% wrong, and it is not 100% right.

    Come back to Volts and Amps to get a clearer picture of what you are looking at.

    Volts can be equated to the volume of flow you are getting out of a length of hose. Amps can be equated to the pressure of the water through the length.

    You can have 500 GPM running out of the end of 6" LDH looking like you could pee further. Put the same amount through a 1 1/2" line and you had better hang on to the end.
    Its the other way around. Volts are similar to the head pressure in a water system, and amps represent how much electricity is flowing through the wires.

  3. #23
    Forum Member firecat1's Avatar
    Join Date
    Sep 2007
    Location
    Betwixt here and there.
    Posts
    3,475

    Default

    I'm not trying to sound stupid here and would just like to educate myself a little: I thought solar panels were usually just on one side of the roof. If so, what would prevent you from venting on the non-panelled side? Thanks in advance for any non-smart@$$ answers.

  4. #24
    Banned
    Join Date
    Jan 2008
    Posts
    8,677

    Default

    Quote Originally Posted by nameless View Post
    Its the other way around. Volts are similar to the head pressure in a water system, and amps represent how much electricity is flowing through the wires.
    Good God, thanks for the correction. It isn't the first time I've had dyslexia kick in....

  5. #25
    Banned
    Join Date
    Jan 2008
    Posts
    8,677

    Default

    Quote Originally Posted by LeatherHed4Life View Post
    Holy old thread batman!

    However... I think the guys that work on the NYC subway would beg to differ
    Gee, are the NYC subways run on Solar?????

    But yes, you can get large DC voltages, they just don't come out of household solar systems.

  6. #26
    MembersZone Subscriber LVFD301's Avatar
    Join Date
    Jun 2006
    Posts
    3,923

    Default

    Quote Originally Posted by MPaiss View Post
    I wanted to offer some clarity to this discussion. It is an area we all need to know about, but as is often the case; a few misconceptions can spin some VERY tall tales!


    4. The inverters that change the power from DC to AC, are powered by AC. If you shut off the main service breakers, the inverter is OFF and there is NO AC power being sent into the structure. There are capacitors in the inverters that can hold a charge for about 5 min, but in the daytime the panels are producing power anyway. When the sun goes down. Everything is de-energized.
    Thank you - there is some great information there.

    I do have one question though - you state the inverters are powered by AC? Every inverter I have used both in PV applications, as well as other applications, provides AC
    from DC, but does not require seperate AC to run. I think it would be incorrect to make
    a blanket statement like you do in item 4.

    Primarily I have remote commercial applications, but I have dealt with some cabin systems also. Most of them will see the absence of AC power just as a power outage.


    To me - the big concern I have when I see solar panels is where is the battery plant,
    the cabling from the batteries to the inverter, and the fact that shutting down the AC commercial power may or may not kill the AC power in the house.

    Chopping through the panels is needless destruction.

  7. #27
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Hi every one,

    I'm not fireman, but a solar designer and just wanted to clarify some of the post here.

    First off, a dc wire can have up 600 volts or even 1000 on some commercial locations. Each cell is only .25-2 volts per cell depending on manufacturer. Many of these cells are strung in series to make a solar panel. Now, several panels (generally 6-20) are strung in series to create a string. A string containing (8) 72 cell modules at 1 volt per cell would be 676 volts. In reality, its not this simple since solar works better when it cold. Systems are designed to only hit any ware near 600 on the coldest extreme on a supper sunny day. They also have different voltages rated at max and normal operating. In reality you could expect over 400 volts in dc wiring. In lower voltage panels/cells, more are strung together, so your seeing roughly the same voltages.

    Secondly, shutting of "dc disconnects" or ac disconnects does not make the panels dead. If the sun is out they still produce power. They may have 0 current, but if you cut a wire and become a ground, current will be much higher. Same goes for shutting off the inverter. the current int he dc wires feeding it is 0 until you cut one and become ground.

    Also, chopping through panels should be a last resort, because then your exposing tons of wiring that could potentially take you as a short cut to ground. Other panels in the series are still powering the damaged one.

    If possible it is best not to disturb the panels and always treat them as hot, unless it is at night.

    There are some great resources on the web about fire fighting a house with solar, but please don't think they are low voltage and wont hurt you.

    -Cody

  8. #28
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Quote Originally Posted by ScareCrow57 View Post
    Gee, are the NYC subways run on Solar?????

    But yes, you can get large DC voltages, they just don't come out of household solar systems.
    Previous in bold is Incorrect

    Household solar array are capable of outputting 600 volts DC and will regularly output over 400.

  9. #29
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Quote Originally Posted by firecat1 View Post
    I'm not trying to sound stupid here and would just like to educate myself a little: I thought solar panels were usually just on one side of the roof. If so, what would prevent you from venting on the non-panelled side? Thanks in advance for any non-smart@$$ answers.
    that's what is recommended for residential solar. Unfortunately this may be more difficult on a commercial flat roof with solar.

  10. #30
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Quote Originally Posted by LVFD301 View Post

    To me - the big concern I have when I see solar panels is where is the battery plant,
    the cabling from the batteries to the inverter, and the fact that shutting down the AC commercial power may or may not kill the AC power in the house.

    Chopping through the panels is needless destruction.
    I'm not sure what type of homes you deal with, but most home connected to "the grid" don't have batteries. They sell and buy power from the grid and use the grid as their battery. You are correct in an "off grid" solar array, but off grid is pretty rare these days.

  11. #31
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Quote Originally Posted by ScareCrow57 View Post
    OK. Basic electricity here. It is impossible to have 600 volts of DC current. In an electrical circuit the Voltage = The Current X the resistance (Ohms Law). Current is measured in Amps. Each photovoltaic cell generates about 0.5 volts. A cell that measures 4.5 x 1.5 will produce 0.5 volts and 1 amp of current giving 0.5 watts. If you connect 120 of these together you will get enough electricity to run a 60 watt light bulb. In order to get say 12 volts DC you would need to connect 24 of these cells in series.
    Most panels have 60-72 cells. Most cells are over .5 volts and way more then 1 amp. These panels are strung together in series multiplying the panel voltage. Even using your numbers the voltage can easily be very high. (.5v/cell) * (72 cells per panel) * 16 panels/string = 576 volts

    As mentioned in an earlier post, its not that simple, but you can see, high voltages do exist.

    Quote Originally Posted by ScareCrow57 View Post
    Next, the solar panels are simple transistor devices with a glass covering. At heats exceeding 150 degrees F most silicon devices fail. Such is the case with these devices. In a fire situation, the danger is non-existent at the panel. The danger exists at the converter where the DC is converted to AC. Even then, it is only 120 volts. Of course this applies to residential use. Industrial systems will be far different.
    First off, solar panels become far less efficient, but don't generally fail until they melt. (burn) Also if 8 panels out of a 16 panel string are failing, you still have half the voltage at those panels. The real danger is the unburned panels melted wires.


    Quote Originally Posted by ScareCrow57 View Post
    Also, if you are attempting to vent through the panel there is little danger. The biggest danger would be the flying glass. The wires connecting the cells are very small. If you were able to create a condition within the panel that would give a large amount of power the wires would melt instantly. Again, the real danger is not in the panel itself. It is in the distribution and converter system
    Glass is general shatter resistant. The small wires under the glass actually carry up to 600 volts. They are small because they are reasonably low amperage. (enough to kill you still) They will still be live and powered by surrounding panels.

    If you do need to break through panels proceed with caution and attempt to fully cover sounding panels with light proof cloth, (not a blue tarp)

  12. #32
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Quote Originally Posted by FlyingKiwi View Post
    Agreed.

    Look at lots of small photovoltaic devices connected together in a panel next time you are near one.

    See the big heavy cables capable of carrying sustained voltages of 600 DC without frying and bursting into flames. Not likely sunshine.

    Yes there is risk, of the system compromising during fire and becoming energised with the house voltages via contact with other wires.

    But if you are going to open up the roof isn't it faster to do it where the point of least resistance exists? Chopping through a panel or going beside it and chopping through the roof?

    Which one would I pick?

    Think... Think... Think...
    General there is a roof underneath the panel. Even int he solar shingle systems there is still normal decking under the roof. Chopping through next to the panel would be much easier and safer if there is space.

  13. #33
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Quote Originally Posted by KB1OEV View Post
    Good catch on the Amps vs Volts thing. I missed it the first time through.

    One other interesting thing, if you happened to put an axe through a solar panel and made a connection across two cells inside, you would only have 0.5V across it, which isn't going to shock anybody.

    I don't see why there would be any appreciable charge left in the solar panels after dark. Is there a large capacitance in the panels themselves? Anybody know?
    Incorrect, all the cell around it and the panels near it are going through those cells. During the day you could have normal system voltages (400vdc) going into you ax.

    At night you are safer, but the panels will pick up a little power from nearby light. Its important to make sure some one checks the next day since wiring may have melted and grounded out. Symptoms of damage may not show until the system fully powers up the next day.

  14. #34
    Forum Member
    Join Date
    Dec 2011
    Posts
    8

    Default

    Quote Originally Posted by len1582 View Post
    Got this the other day and feel it's worth passing on..


    Even if it's nighttime and the solar panels have not been exposed to direct sunlight for several hours they still are energized and can kill you. It is estimated that the panels would need to be covered with an opaque tarp for 7-10 days before the panels will "de-energize" down to minuscule levels. (although the handouts specify that this is an option for safety steps - it is not accurate per the presenter)
    TOTALLY INCORRECT

    Inverters are the only parts that have capacitors that store energy and they loose it after 10-15 min. Panels do power a little bit in very low light but don't store power. Generally ambient night light will only power a few volts throughout the system and wont be enough to do any real harm. That being said, precaution should still be taken, but they wont send tons of power at night and certainly don't store any.

  15. #35
    Forum Member ThNozzleman's Avatar
    Join Date
    Jun 2002
    Location
    Jefferson City, TN
    Posts
    4,334

    Default

    Normally, guys here rip on resurrected threads, but this one was worth the once over just to see the words "Scarecrow" and "Banned" again.

  16. #36
    Forum Member DeputyChiefGonzo's Avatar
    Join Date
    Aug 2000
    Location
    Somewhere between genius and insanity!
    Posts
    13,582

    Default

    Quote Originally Posted by ThNozzleman View Post
    Normally, guys here rip on resurrected threads, but this one was worth the once over just to see the words "Scarecrow" and "Banned" again.
    It still warms the cockles of my heart!
    ‎"The education of a firefighter and the continued education of a firefighter is what makes "real" firefighters. Continuous skill development is the core of progressive firefighting. We learn by doing and doing it again and again, both on the training ground and the fireground."
    Lt. Ray McCormack, FDNY

  17. #37
    Forum Member
    Join Date
    Jan 2012
    Posts
    1

    Default

    I studied your thread and really seems to be very dangerous situation and talk is how to handle that type of situation. While searching online I found many solar system service providers give necessary tool kits with them to avoid such situations.

    solar panels florida

  18. #38
    Banned
    Join Date
    Feb 2012
    Posts
    1

    Default

    For those of who donít know, solar is actually produced from a procedure that occurs within the sun known as nuclear combination. Nuclear combination is actually the very same procedure that is involved in nuclear power plants & actually engages the same basic nuclear science regulations that relates to atomic bombs.

  19. #39
    Forum Member FWDbuff's Avatar
    Join Date
    Jul 2003
    Location
    Pee-Ayy!
    Posts
    7,390

    Default

    Quote Originally Posted by alexisrois View Post
    For those of who don’t know, solar is actually produced from a procedure that occurs within the sun known as nuclear combination. Nuclear combination is actually the very same procedure that is involved in nuclear power plants & actually engages the same basic nuclear science regulations that relates to atomic bombs.
    ok, and........?
    "Loyalty Above all Else. Except Honor."

  20. #40
    55 Years & Still Rolling hwoods's Avatar
    Join Date
    Jun 2002
    Location
    Glenn Dale Md, Heart of the P.G. County Fire Belt....
    Posts
    10,739

    Default

    God, I hate waiting for the other shoe to drop.......
    Never use Force! Get a Bigger Hammer.
    In memory of
    Chief Earle W. Woods, 1912 - 1997
    Asst. Chief John R. Woods Sr. 1937 - 2006

    IACOJ Budget Analyst

    I Refuse to be a Spectator. If I come to the Game, I'm Playing.

    www.gdvfd18.com

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Venting Roofs with Solar Panels
    By malba49 in forum Firefighters Forum
    Replies: 12
    Last Post: 10-18-2009, 02:32 PM
  2. Utility Control: Solar Panels?
    By cowbucks06 in forum Fireground Tactics
    Replies: 13
    Last Post: 08-21-2008, 07:44 PM
  3. Solar Panels on the Firehouse
    By ChiefKN in forum Firefighters Forum
    Replies: 12
    Last Post: 08-08-2008, 10:26 AM
  4. solar panels.
    By frenchfireball in forum Firefighters Forum
    Replies: 0
    Last Post: 02-18-2008, 07:39 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts