I am running ten Cree XR-Es from a Meanwell 350mA driver connected to a 120VAC GFI outlet. Because the wiring passes through my attic I want to make sure my circuit and wiring are protected in case of a driver malfunction. Would a 0.5 or 1 amp fast-blow fuse attached to the + output of the driver protect my wire from a fire?
Fusing mains-powered arrays
- Thread starter asimba2
- Start date
Steve K
Flashlight Enthusiast
That's an interesting question. I'd recommend selecting the wire based on the use of non-flammable insulation. ... or at least ensure that the insulation is rated for the same temperatures as typical house wiring. In general, I think that a 1 amp fuse would be more than sufficient to avoid melting the insulation on wire that is 22 ga or larger. It's surprisingly hard to get a wire hot enough to cook the insulation.
I'd worry more about the Meanwell driver failing in a thermal event. Do you have a fuse in line with the mains power? Or do you have the Meanwell driver mounted in a metal enclosure?
I'd worry more about the Meanwell driver failing in a thermal event. Do you have a fuse in line with the mains power? Or do you have the Meanwell driver mounted in a metal enclosure?
There is no fuse now. I know most on here indicate that a LED will fry before a fuse will blow, and they rely on that and the driver's internal protection. They may be right, but I would like more than that since some LEDs can fail closed.
Right now the Meanwell is attached to sheetrock in the garage; no enclosure. And just to clarify, the wire is attached to the wooden roof trusses and not passing through insulation.
Right now the Meanwell is attached to sheetrock in the garage; no enclosure. And just to clarify, the wire is attached to the wooden roof trusses and not passing through insulation.
taqueso
Newly Enlightened
A 3/4 or 1-amp fuse would be about right and won't have any negative effect on the circuit. I think Steve is right about 22ga being an appropriate minimum size. You can check out an ampacity chart here: http://www.powerstream.com/Wire_Size.htm
edit: I would add a fuse before the driver (on the AC), as well. If the input power fuse was sized well, you wouldn't need one on the output at all.
edit: I would add a fuse before the driver (on the AC), as well. If the input power fuse was sized well, you wouldn't need one on the output at all.
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Is the power supply current limited? If it is, that will likely suffice for protection on the output side.
That said, if the wire is exposed, then there are regulations concerning what type of wire that is and what the minimum gauge is. The current capacity of that wire will be well beyond a 1 amp fuse and dependent on the driver, what the driver is capable of. I would need to check the NEC again, but the current limiting on the power supply will likely suffice. I believe you are limited to 18 gauge or higher for indoor wiring even though it is class-II low voltage/current. You used to be able to use smaller wire, but that was changed. If I am not mistaken, the newest NEC also called for ClassII wire to be jacketed.
Though fuses are there to protect the wire, it is not that often that overloaded wires are the cause of fires. More often it is an exposed failed connection with resistance in the connection that leads to fires. I believe even ClassII circuit need junction boxes for connections in the new NEC, but don't quote me on that.
Other thing to consider is your power supply. That Meanwell supply is likely "recognized" not listed. A recognized component is only certified to be part of an overall certified system. I.e. as a component in a light fixture that will get overall certification. Translation is that the certification is meaningless for what you are using it for. Odds are it is not certified for open installation and needs and overall enclosure. I would check the specific unit you are using.
Semiman
That said, if the wire is exposed, then there are regulations concerning what type of wire that is and what the minimum gauge is. The current capacity of that wire will be well beyond a 1 amp fuse and dependent on the driver, what the driver is capable of. I would need to check the NEC again, but the current limiting on the power supply will likely suffice. I believe you are limited to 18 gauge or higher for indoor wiring even though it is class-II low voltage/current. You used to be able to use smaller wire, but that was changed. If I am not mistaken, the newest NEC also called for ClassII wire to be jacketed.
Though fuses are there to protect the wire, it is not that often that overloaded wires are the cause of fires. More often it is an exposed failed connection with resistance in the connection that leads to fires. I believe even ClassII circuit need junction boxes for connections in the new NEC, but don't quote me on that.
Other thing to consider is your power supply. That Meanwell supply is likely "recognized" not listed. A recognized component is only certified to be part of an overall certified system. I.e. as a component in a light fixture that will get overall certification. Translation is that the certification is meaningless for what you are using it for. Odds are it is not certified for open installation and needs and overall enclosure. I would check the specific unit you are using.
Semiman
The power supply is current-limited by a Meanwell LPC-20-350 driver. The wiring is solid core 18 gauge and I think I ended up with around 200' of wire total. The project thread is located here, but in summary I have a GFI outlet, then a timer with the Meanwell constant current driver plugged into it, then 200' of 18 gauge solid core with 10 Cree XR-Es at 350mA to serve as eave lighting around my home. If it's better to put the driver in a metal box, I can do that but I worried about heat dissipation.
I welcome any comments you may have...I love the lighting system but want to make sure it's as safe and legit as possible. SemiMan, your text was particularly helpful.
I welcome any comments you may have...I love the lighting system but want to make sure it's as safe and legit as possible. SemiMan, your text was particularly helpful.
It is probably not any better or really safer in the box, but it is likely required for code.
I found a draft of the 2011 NEC, http://www.nfpa.org/assets/files/pdf/rop/70-a2010-ropdraft.pdf You will likely need to pay for a release copy.
The project looks great. It is a great example of power savings. Far better than a ton of 50W halogens.
Semiman
Thank you, I absolutely love the lighting. I have received a lot of complements from neighbors and friends and I love the security aspect. The fact that the house is lit all the way around and only pulling 12W total is just fantastic.
I want this setup as legit as possible, so I will place the driver in a metal box. I still like the idea of fusing it though, so would a 3/4 to 1 amp fuse on the output of the driver be the best bet?
I will certainly read through the code you linked, thanks you.
There is absolutely no harm in adding the fuse to the output and I always say whatever makes you sleep better at night is a good thing. Inspectors understand fuses a lot better than inherent current limiting as well.
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