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Why we use fuses.....

Discussion in 'The Family Room' started by DrNeutron, Dec 17, 2014.

  1. DrNeutron

    DrNeutron Just starting in this crazy hobby

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    I posted this on DIYC, but I wanted to share here as well since a lot of the information I have gleaned over the past couple years have been from both sites and the professionals in this forum offer the same advice about wiring.

    Display has been running since December 1st with a few small hiccups (one tripped GFCI), this was actually amazing considering it has been raining for a week or more....
    Took dog for a walk as I always do around 8PM and walked past the 8 or 9 cars parked enjoying the show when I received a frantic call from my wife about 15 minutes into my walk. A lady came to the front door to tell her my talking tree was on fire! I ran home and the show was still playing along (pixels and dumb RGB were fine) but the 6ft talking tree was dark (AC, made out of led rope light). I quickly took a flash light but could not see anything burnt and no damage to house. I let the sequence finish and shut everything down. I took a ladder out and climbed up to detach the tree and this is what I found:
    burned_wire_shrunk.jpg
    Thank God I had the SSR fused.....fuse blew and all I lost was a section of LED rope light.
    Guys may think it is a waste of money to fuse things with a small load (in this case it was a 6ft section of rope light, can't get much smaller than that for draw), but when the experienced electricians and electrical engineers on this forum (of which I am not, just a computer geek) recommend you follow some general safety guidelines it is a good idea to do so.....
    I just want to say I am grateful for the insights from the professionals on this forum and a huge Thanks for showing newbs like me the safe way to enjoy this hobby.
     

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  2. gerry

    gerry Senior Elf

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    Glad that it ended safely !
     
  3. Bird

    Bird Proud LOR user

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    Glad it was nothing serious.
    Thanks for sharing the reason for safety 1st.
     
  4. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    Im glad this didnt turn out to be something more.

    This is why im not a fan of mains voltage lighting like this, be it 110v or 240v. The reason being is that mains voltage will produce more energy compared to that of low voltage DC lighting thus increasing the risk of fire. When using 12vdc & 5vdc power supplies then the highest the current will go is to the rated limit of the power supply and then the power supply would shut down.

    The amount of energy between 12vdc and 110vdc and 240v can be shown here

    Using 12vdc with a 350 watt power supply will produce approx 370 watts of power before the power supply will shut down on overload protection
    Using 110v mains voltage with a 20 amp fuse/CB will produce over 2200 watts before blowing/tripping the fuse/CB
    Using 240v mains voltage with a 20 amp fuse/CB will produce over 4800 watts before blowing/tripping the fuse/CB

    So as you can see the higher the voltage the more energy needed to trip the circuit which means the higher chance of creating a fire. Fuses can help with this but really need to be put on each output to be of any real value or else reduce the fuse rating on the controller main fuse (LOR users)

    I myself witnessed this a few years back when i still was using 240v mains rope light and after some rain i turned back on the lights to then see smoke and fire as the lights had shorted due to the rain.
    I have also got an electric shock before from mains voltage rope light due to a mains conductor that was exposed through the rope light moulding.
    It was after these incidents that i started to look at low voltage alternatives because as an electrician i find it crazy that we use mains voltage in our front yards in all types of weather with kids touching everything. In the US its not as bad with 110v
     

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