I am working on an LED panel video wall project made up of 3x8 squares of 128x128 pixel panels. Each panel has a worst case power draw of 65W and typical of 35W. I can get the panels as either 24V or 48V supply voltage (an embedded DC to DC switcher will make 5V for the LEDs). I plan to put the 24V or 48V power supplies in a NEMA box at floor level and run power cables 10ft up the wall (either inside the wall or in a raceway enclosure). Space constraints won't allow me to put the power supplies in or near the video wall.

I am leaning toward choosing the 48V supply to reduce the current through the power cables. But I am confused by the NEC specifications for low-voltage systems in this case. Some sections refer to less than 50V, Article 411 Low-voltage lighting uses less than 30V, Table 11 says Class 2 power supplies between 20 and 60V. Does the low-voltage lighting section apply to this case? Would the 24V panels be a safer route to meet NEC requirements? Am I missing an obvious section in the NEC that would apply to powering a video wall with 24VDC or 48VDC?

Also, in Table 11a on Class 2 power supplies, they set the maximum VA to 100 for 20-60V supplies. Does that mean that I need to use 16 100W power supplies? But then to have less than 100W per power cable, I would need to run 24 separate cables to each panel since 2 panels combined could add up to over 100W. Then I would need 24 100W power supplies. This seems absurd to me, I must be misunderstanding the NEC. I would prefer to use 6 300W or 4 500W supplies, then run 6 or 4 separate power cables up to the video wall and distribute the power to each panel. Is there something in the NEC that would allow this?

I appreciate any feedback on this.


Since your application demands up to 2kVA LVDC this NEC class 2 of product is not desirable. You want a LED driver that is UL60950-1 compliant and 48V is a wise choice since 50A cables are rather heavy gauge. Look harder for an opportunity to locate it close to the load.

Without more details I might suggest 48V LED strings with http://www.meanwell.com/productPdf.aspx?i=366 Does this work for you?? Have a hot spare for reliability or current sharing.


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