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Thread: This is why we fuse everything.....

  1. #11
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    Default Re: This is why we fuse everything.....

    Awesome post RGB_Mixer, very informative!

    FYI, on this point " I noticed in the picture all that tape around the connection. I would only wonder how long it had been taped? Done for waterproofing? Moisture will get under the tape, corrodes the contacts - the contacts create resistance - the resistance causes heating - eventually the contacts fail. The photo tells me that damage was mostly from overheating caused by trapped moisture corroding the contacts. Rope light, 2 little pins and a nut? The tape covered up the pending failure. The first clue was the tripped GFCI - Good man! U used the safety tools!
    Unfortunately, the LED rope light I purchased had power connectors that were not rated for outdoors. To combat this, I used liquid tape around the connections, then applied rubberized tape (used all the time when installing satellite ORU's) and wrapped with black electrical tape (this is just to hold the rubberized tape in place until it sets). Somehow, water must have gotten in or maybe I was a little too rough when mounting the tree and caused a short. I am just happy the fuse did its job before anything bad could happen.
    Here is one question maybe you could answer.
    Looking at the Tree later on I realized it was not on an SSR from my Ren32 (in which all SSR's are fused as well) but on an old LOR box. The 30 amp fuse blew on the controller but the GFCI did not trip.
    This is undoubtedly why the wire fried like it did. Why wouldn't the GFCI have tripped before the fuse blew? Is it because the fuse reacted faster? I have since tested the GFCI and it works fine (tomato cage mini trees are fun.....NOT)

  2. #12
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    Default Re: This is why we fuse everything.....

    Definitely helpful info! But the question still remains - where do I go to find inline fuses or, I suppose, preferably a fuse patch cable of sorts I can just stick on an extension cable?

    My Renard controllers have fuses on board, so I'm less worried about those. I'd like to fuse the AC side of my DC supplies for my pixel tree and flood lights. They'll have fuses on the DC side but that still leaves open a chance of bad things if, say, metal somehow bridged the terminals or something (really low change but I'd like to be thorough)

  3. #13
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    Default Re: This is why we fuse everything.....

    on the +12V output of the power supplies I used this 30A circuit breaker http://www.delcity.net/store/search/...jsp?item=75135
    Attached Images Attached Images

  4. #14
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    Default Re: This is why we fuse everything.....

    I think we found someone's sweet spot VBG. Thank you for a great post!
    2009 - 48 channel MegaTree 4800 lights
    plus 3200 lights static display.
    2010 - 6 Snowflakes on heavy equipment stored in front yard :-(
    2011 - 72 channel Megatree 7520 lights,
    120 channel total about 10k lights total

  5. #15
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    Default Re: This is why we fuse everything.....

    Quote Originally Posted by m00dawg View Post
    Definitely helpful info! But the question still remains - where do I go to find inline fuses or, I suppose, preferably a fuse patch cable of sorts I can just stick on an extension cable?

    My Renard controllers have fuses on board, so I'm less worried about those. I'd like to fuse the AC side of my DC supplies for my pixel tree and flood lights. They'll have fuses on the DC side but that still leaves open a chance of bad things if, say, metal somehow bridged the terminals or something (really low change but I'd like to be thorough)
    There is a fine line between being cautious and over-cautious.

    Agreed, fusing the AC side is a good idea so if the PS takes a crap you don't take down everything - good logic. However! Gotta love exceptions! ALL switching power supplies have their own internal fuse mounted to the circuit board ... I've repaired quite a few units (bad caps cause AC overloads) and you'd never notice the fuse on the board unless you've been doing repairs for awhile. I have YET to toss any LCD monitor or TV because it died. Fix the power supply, replace the fuse with the EXACT part and it's a happy camper again. I usually fix these sort of things for friends and family. $1000 TV saved with a handful of capacitor(s) and a new fuse. Cost? Go buy a SIX PACK! I use many switching power supplies and have yet to find one that isn't internally fused.

    I believe fuses are required to get a "UL" or "CSA" sticker - otherwise a failed power supply could easily cause a fire. I don't care where they are made, one bad cap or MOSFET could easily destroy the entire unit so fuses are integral to the units today. YEARS ago we used transformers (some really HEAVY ones), diodes and filter capacitors for DC. You had to fuse the PRIMARY because it had no protection. Technology has advanced quite allot from the "OLD DAYS".

    I wouldn't worry about the AC side of the power supplies at all. Just don't overload the extension cords. That is key to a happy power supply. MOST power supplies have a FINGER GUARD that helps protect those 120v terminals. Honestly, if something gets in there that shorts the Line and Neutral, it got there because it wasn't suppose to be there and/or wasn't properly protected to begin with. Let the circuit breaker handle it. That's why they are there.

    Once that cover is closed, that is all the protection you should ever need. If you need additional peace of mind - put a padlock on the cover.

    I've never fused switching power supplies. I know they are already fused. Protected from overload and output shorts. It is part of their primary function. Short their outputs and it will shut down and stay that way until the AC power is cycled on again.

    Rest assured you are covered. Your concern is valid and I hope I've shed some light on this.

    If you still feel strong about fuses - get some inline fuse holders rated for 250v usually a hard plastic or bakelite and has #16 or larger wires on them. Splice it to the HOT side inside the controller box. Fused at 125% to allow for current inrush on startup. Here is where Slo-blow fuses are used. Some math using Ohm's Law and choose the closest fuse, never going lower so go to the next highest 'standard' size. Some of these power supplies have a pretty high current inrush. I pissed off my circuit breaker a few times (Square D, fastest breaker on the planet) and eventually had to STAGGER start them or put them on separate circuits. I staggered them because I had the parts to do that and it made it easy to use for OTHER shows where I might not have extra circuits available.

    Happy Holidays!

    Eddie

  6. #16
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    Default Re: This is why we fuse everything.....

    Ah I didn't think about internal fuses on PSUs. Is that true too of the laptop power supplies many folks around here (including me) might be using for the DIYC floods? The other DC supplies I'm using are 2 12V waterproof ones and a 12V for the E682 (I believe all from diyledexpress). I would imagine those have internal fuses.

    Still, I'm surprised I can't find more in-line options. It's not like a glass fuse is expensive and the expected load is known for everything. Certainly it'd be easier to replace than having to open up a PSU (though hopefully they use the resettable fuses).

    Anyways thanks for the info!

  7. #17
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    Default Re: This is why we fuse everything.....

    Quote Originally Posted by DrNeutron View Post
    Awesome post RGB_Mixer, very informative!

    FYI, on this point " I noticed in the picture all that tape around the connection. I would only wonder how long it had been taped? Done for waterproofing? Moisture will get under the tape, corrodes the contacts - the contacts create resistance - the resistance causes heating - eventually the contacts fail. The photo tells me that damage was mostly from overheating caused by trapped moisture corroding the contacts. Rope light, 2 little pins and a nut? The tape covered up the pending failure. The first clue was the tripped GFCI - Good man! U used the safety tools!
    Unfortunately, the LED rope light I purchased had power connectors that were not rated for outdoors. To combat this, I used liquid tape around the connections, then applied rubberized tape (used all the time when installing satellite ORU's) and wrapped with black electrical tape (this is just to hold the rubberized tape in place until it sets). Somehow, water must have gotten in or maybe I was a little too rough when mounting the tree and caused a short. I am just happy the fuse did its job before anything bad could happen.
    Here is one question maybe you could answer.
    Looking at the Tree later on I realized it was not on an SSR from my Ren32 (in which all SSR's are fused as well) but on an old LOR box. The 30 amp fuse blew on the controller but the GFCI did not trip.
    This is undoubtedly why the wire fried like it did. Why wouldn't the GFCI have tripped before the fuse blew? Is it because the fuse reacted faster? I have since tested the GFCI and it works fine (tomato cage mini trees are fun.....NOT)

    Interesting thought ... tomato cage.

    Here's a pretty simple picture how GFCI works: http://www.nationshomeinspections.co...og-GFCI-1c.jpg

    GFCI devices are 'differential' sensors. In the simplest way: current must flow equally in both directions for the GFCI outlet to remain ON. As soon as it detects one side is higher or lower than the other, POP goes the weasel!

    Here's an interesting fact. I can hold any HOT wire all day long and never trip a GFCI. WHY? Well, why do it at all? Point is: I will be at the same potential as long as I am NOT GROUNDED anywhere, current will not flow. That picture shows the GREEN GROUND. That is your body grounded somewhere and current wants to flow to ground. That's why birds perch on wires and never get fried. GFCI devices sense this deviation >3-4milliamps and open the circuit.

    There are volumes of techno babble in regards to the hows and whys.

    Another interesting fact: I can put a 2 conductor live extension cord protected by a GFCI device into a PLASTIC bucket of water and that GFCI will NOT trip. You stand a better chance tripping the circuit breaker first. NOW ... do the same thing with a 3 conductor extension cord, properly grounded at the outlet ... POP! There was current deviating from the HOT to GROUND, not back to the NEUTRAL. I would venture to say MOST people with GFCI problems are due to 3 wire cords becoming saturated and conducting enough current to trip the GFCI.

    In a 2 wire situation, if there was a strong enough path to ground, the GFCI would have tripped. Hospitals, for instance (and memory serves me correctly) has a maximum trip of <3.5 milliamps for GFCI devices. Hospital grade devices outdoors? I think most people would loose their minds because that GFCI is too sensitive. There is extremely detailed information to current vs live wire exposure tables and tons of research paper. All comes down to the device is designed to protect PEOPLE from potentially lethal exposure to electric.

    It sounds like you took the time to do it right - good precaution - rubber tape under vinyl - self vulcanizing.

    You mentioned it is an LED rope? It needed some sort of power control then. Voltage and current limiting. That could be why it has such a big hole in it. That part of the connection had the components in it, it failed and burned up and during that time it shorted out across the hot and neutral which took out the fuse. Triacs are pretty forgiving on high current for fractions of a second. If there had been a slo-blow fuse in there, that triac might not have survived. You can also DOWN SIZE the fuse based on the total current draw. If you have a bunch of LEDs on it now, you could easily drop to a 10A fuse - that is a 1200 watt maximum but size the fuse for 125% of the total load and if you can't get the exact size, use the next highest standard size. Obviously never ever put in a larger fuse (good thing AGC fuses are limited to 30A)

    I believe OLD LOR stuff used a standard AGC glass fuse. Many current sizes are available.

    Although basic electronic components can last for MANY years and in all sorts of environments, it sounds like this particular unit didn't get the memo and wasn't interested in the averages.

    Yup ... many of my ssr's are protected by a poly fuse. My primary 120/240v power distribution panel has industrial style cartridge fuses (finger safe) on DIN rail for all the 25A SSR's. The fuses are rated to protect the wire they serve. #16 wire = 10a, #12 wire = 20A, etc. The tables and such can be found in the National Electrical Code and many sources on the internet.

    Here's the Underwriters Lab guide to extension cords: http://www.stayonline.com/reference-...-ampacity.aspx

    I use allot of twist lock style power connectors for my AC power. Costs more but much easier to use big wire instead of MANY little extension cords. One cord instead of many - easier cleanup.

    Hope the GFCI puzzle goes together well

    Thanks for letting me help.

    Happy Holidays!

    Eddie
    Last edited by RGB_Mixer; 11-13-2015 at 04:35 PM.

  8. #18
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    Default Re: This is why we fuse everything.....

    Thanks for taking the time for the excellent explanation.


    Sent from my iPad using Tapatalk
    Phil

  9. #19
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    Default Re: This is why we fuse everything.....

    Yes, following with great interest.

    Very informative.

    Thank you,

    Shane

  10. #20
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    Default Re: This is why we fuse everything.....

    Quote Originally Posted by m00dawg View Post
    Ah I didn't think about internal fuses on PSUs. Is that true too of the laptop power supplies many folks around here (including me) might be using for the DIYC floods? The other DC supplies I'm using are 2 12V waterproof ones and a 12V for the E682 (I believe all from diyledexpress). I would imagine those have internal fuses.

    Still, I'm surprised I can't find more in-line options. It's not like a glass fuse is expensive and the expected load is known for everything. Certainly it'd be easier to replace than having to open up a PSU (though hopefully they use the resettable fuses).

    Anyways thanks for the info!
    Hiya - as a general rule (looked a bit deeper into this just to keep me on track) ... consider where a laptop PSU is used. If one were to fail without a fuse and start a fire - nope, the manufacturers don't care to carry that sort of liability. No manufacturer in their right mind wants that sort of liability. Fire forensics specialists can identify the source of just about any type of ignition source.

    To get a Underwriter's Laboratory approval the PSU must protect itself. So, it has a fuse and other protections. Consider the MILLIONS of these things everywhere we go today. A PSU goes bad - well, we just toss it and buy a new one. No Coroner's report is filed. LOL!

    Oh gawd no ... a circuit breaker style?? Nope - too expensive and the size of the device - those things CAN fail - if a switching PSU blows its fuse, it has internal issues. Most of them shut down if overloaded and reset when the overload clears - same for dead shorts on the outputs. It could be called PSU Self Preservation Mode. Those crazy engineers have other rather flat explanations but it all comes down to keeping people safe. Some IDIOT will try to replace a fuse with a LARGER fuse or worse ... HOLY SMOKE! Or was that BLUE SMOKE? I forget - >GRIN<

    Overload a switching PSU and it will try to keep up until the internal thermoster begins to cut back output. Like I said earlier - short a switching PSU and it is suppose to shut down until the unit is power cycled. It checks the output for a short before beginning its startup sequences - takes a few milliseconds. If it is cleared, it resumes its happy job and gives you the power you want.

    Today's switching power supplies are intelligent compared to their early counter-parts 30 years ago. IBM can attest to that - some PC's in the early 80's started fires. Nope, no one really heard of those instances - back then there was no internet like today. Google was STILL in diapers. Back then ... IF you had DIAL UP, you must have been rich. Not too many people remember CompUserve or AOL dial-ups? 10 cps teletypes? 30 cps video terminals? Yeah, I used them back when. Cable modems were a dream I had in the early 80's ... go figure. Took them long enough.

    Keep the faith. If ever in doubt, you can surely find all the information you'd ever want to know by power supply model number. I can still dig up specs and schematics on some of the older stuff I've come across.

    Confused by the info you get? No worries. If I can help clear it up ... I'll be around.

    Eddie

    P.S. finding INLINE fuse holders is not difficult ... they still come in varieties and different flavors with wires already attached. I can't remember ever using one in many years except in automotive applications. Yes, they are becoming scarce - a dying breed of protection because most devices are built with internal protection. Even the USB port we use is current limited. Technology gives us some peace of mind - it is smarter than ever before and safer too. -Eddie

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