![]() Looking at this differently, what's the impedance of a 100 watt load at 70 volts? I remember that watts = volts squared divided by impedance, so impedance = volts squared divided by wattage (70 x 70)/100 gives 49. For example, a 100-watt load can go 700 feet on 18 gauge the same load may be placed on 1100 feet of 16 gauge. Stepping up to 16 gauge wire extends the allowable run length by approximately 35%. Conversely, if you half the load, you may double the acceptable wire length, i.e., a 50 watt load is safe over 1400 feet of 18 gauge. If you double the load (sum of your tap settings), you will reduce the footage by half, to 350 feet. I know a great distributor on this stuff too (Fred).Ĭ.Wire Length -18 gauge is appropriate up to 700 feet with a 100-watt load. I think the 16 AWG pulls nicer too and has less chance of getting hurt by other people in the ceiling.Ītlas sound had a nice rule of thumb (below) and they also have some good articles on their website. Plus there's no concern on 99% of your systems since you won't overload the 16 AWG during installation or when they want additional speakers. You can use 18 AWG on the smaller stuff but I personally like stocking one or two wire gauges and I already have 14 and 16. I normally use 16AWG for everything and have never had a problem. I just have a hard time thinking of using an alarm wire (22/2) or smaller for those single speaker runs.īTW, in no situation is my single wire longer than 100 feet.Ĭable Wire Runs for 70v distribution systemsĪWG Wire Size - Resistance1000’ (300m) - Current - Power I don't know if I'm not wasting client's money by not running smaller, less expensive wire. office, bathroom, etc) where they will be tapped at 2.5W to max of 5W. ![]() The reason I started looking at it, is because I'm wiring a job right now using 16Ga for each of the single speaker runs (Dr. I would never do something that extreme, but is the math right? My calculations show that using 70V RMS or even 100V Pk at 2 Watts, the current is only 0.02 AmpsĪm I correct in reading and understanding that I could put up to 70 Watts! worth of speakers on a single pair of 18 gauge wire? Tapped at 2 watts, that would be 35 speakers! In doing some simple calculatrions based on 70V (RMS, 100V PK) and having 2 speakers tapped at 2Watts, it looks like I could do it with a hair thin wire. I'm doing some searches, but can't find a simple calculator or chart beyond this one: ![]()
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