1 led strip = 3a, 36w, 12v, 16.5ft …………..6 strips= 18a, 216w, 12v, 99ft
Will this transformer/ power supply (20A, 240w) be capable of handling the 6 strips with the specs mentioned above? Each strip has on its end an external female power adapter that can be plugged with any 3a male power adapter.
1- Which gauge of wire would be sufficient to use for power supply to the female adapter, I have 100ft of 12AWG and will option 1 of having the transformer in middle and run 50ft to left and right be best or with a 30A, if that.
2- Will running two 20a transformers linked to that ONE power feed cause issues?
// Each strip are connected to one another and power on but dim thus the need for external power. I think of it more like a water hose being pushed by two outlets from each end to maintain pressure 😀
Best Answer
The power supply seems to be capable of driving the whole strip chain.
If you run the supply from only one end of the chain, there will be voltage drops. Because, first strip draws 3A and the remaining 15A flows through its copper tracks. Then second strip draws 3A and the remaining 12A flows through its copper tracks. Then third strip draws 3A and the remaining 9A flows through its copper tracks ...and so forth. This means, there will be a couple of voltage drops on the strips which results in brightness decrease from one end to another. That's why the supply should be applied from both ends.
1) The current need of cables for each option is about 9A. According to the table on this page (http://www.engineeringtoolbox.com/wire-gauges-d_419.html) at least AWG #16 will be sufficient.
OPTION 1: If you use AWG #12, the cable resistance of 50ft will be 0.08ohms and the voltage drop on each cable will be about 9A x 0.08 = 0.75V. So, input voltage on the strings will be about 12 - (2 x 0.75) = 10.5VDC. This will cause a decrease of brightness, clearly.
OPTION 2: If you use two separate power supplies and make the connection cables shorter, this will give you a better result (i.e. nearly no voltage drops on the cables).
Note that there will be a little and equal amount of brightness decrease on LED3 and LED4.
2) If you run the power supply from both ends of the strip chain (OPTION 2 with one supply or two), strip 3 and 4 shouldn't be connected to each other. Because you apply the supply voltage from both ends.