August 1, 20196 yr 3 hours ago, MartinCoetzee said: I have always just fused my positive side, what is the feeling on this ? The rule is apparently that if the system is floating, then you must fuse both sides. If one side is grounded, then you fuse only the ungrounded side. For most inverter setups this would mean you have to fuse both sides. I personally have only the positive side fused, but that is because my layout is such that a ground fault is really not expected. The reason, which I admit I don't fully understand yet, is when you have multiple earth faults (ie current jumps across to another conductor, eg the chassis of a vehicle, and back onto the same conductor or the opposite side), then the fuse on that side might be rendered useless or some current might bypass it and cause it to not blow. The fuse on the other side then protects you. Since this can happen on either side, you need to fuse both sides. For my PV cables, which leave the house and go into a harsher territory, hence faults are more probable, both sides are fused. Edit: Here is a quote from another site about a DC control system: Quote With a floating supply, as noted, first or subsequent ground fault(s) on one leg does nothing other than ground the supply. First fault to ground on the second leg, blows both the positive AND the negative fuse when both legs' fuses are a single and same rating fuse in the fault current path (assuming both are fast-blow fuses). This will indicate which circuit conductors (or equipment) on which the faults have occurred. If you have several ground faults on one leg, those circuits' fuses will parallel the fault current and may not blow. So if you only have one leg fuse blow, you should be looking for several ground faults on the other leg. When both positive and negative fuses blow, and clear the fault from the system, the system is returned to floating status... while the faulting circuit and or equipment can be repaired or replaced. Edited August 1, 20196 yr by plonkster
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