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Old 07-06-2016, 04:28 PM
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hanleyclifford hanleyclifford is offline
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Quote:
Originally Posted by BunnyPlanet169 View Post
Hanley - I really don't understand where you're going here. Are you dissing the NEC and ABYC? These are well intentioned, and well supported fire safety codes.

3% is an excellent design goal, and inherent in that calculation is the circuit design current, ampacity of the wire, the temperature of the space, and ultimately the fuse requirements.

Numbers greater than 3% will work, no doubt for a while, but the risk is a runaway thermal reaction - as voltage drops, the current goes up, heating the wire, which increases it's resistance, which further drops the voltage, which increases current, which eventually burns the insulation and shorts.

I've burnt up extension cords doing just this.

I don't know why you'd want to recommend ignoring this.
I do not recommend ignoring anything useful. However, of far greater importance than arbitrary goals is the design and propagation of an electrical system, "tree" if you will. The only good voltage drop is the intentional one, and we have seen here a number of unintentional voltage drops that had useful results. I follow the rule that no wire should be larger than the wire that feeds it. You would be surprised at how many violations of this occur. Similarly, no wire should feed more than one wire equal to itself, or any combination greater than itself. This is one reason why coil + should remain as clean as possible. There is a lot more to building a clean, safe and effective system than rigid adherence to arbitrary numbers. If voltage drop is a big priority (as it should be), here is a practical suggestion: start the system with the largest wire practicable for present and any future considerations. For me that means #2 cable coming off the batteries, both red and black, and ganging them up to a big buss bar before distribution.....maybe we should start a thread on DC system construction?

Last edited by hanleyclifford; 07-06-2016 at 04:37 PM.
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