MultiPlus 24/2000 Cable vs. Fuse Sizing

[tobascodagama]

I'm looking at the documentation for the MultiPlus 24/2000 there seems to be a discrepancy in recommended cable sizes vs. fusing.

The 24/2000 manual specifies a 200A fuse on the DC input but then goes on to give a recommended cable cross section of 35mm². The Wiring Unlimited booklet in the DC wiring section also presents an example of a 2400W inverter load at different battery voltages, where the 24V input cable is carrying 100A and gives a recommended cross section of 35mm².

My understanding is that fusing and cables should always match the maximum amperage on that branch of the circuit. So if the 24/2000 DC input expects to potentially handle 200A, then that implies the cabling and fuses between the inverter DC input and the batteries (and the battery bank itself) should also be capable of 200A. Yet they recommend 35mm² for the cables, which should only be capable of sustaining 100A.

What am I missing here? Which maximum amperage value is correct?

 

[snoobler]

2000/24 = 83A

Double for surge = 166A

Fuses should be sized for the wire X 1.25.

Wire can always be bigger than the current dictates.

35mm2 is a little thicker than 2awg and can easily sustain 150A+ with 105°C wire. The 200A is approx the wire capacity X 1.25.

Maximum amperage depends on resource used and is determined by how hot the wire can get without melting the insulation. Common ratings are 60, 75, 90 and 105°C.

Victron recommendations appear consistent.

 

[tobascodagama]

35mm2 is a little thicker than 2awg and can easily sustain 150A+ with 105°C wire. The 200A is approx the wire capacity X 1.25.

Ah, that clarifies it then. I was only considering the 75C ratings, so the ~1AWG wire recommendation looked much too small.

2000/24 = 83A

Double for surge = 166A

This also answers the follow-up question that I had, about the battery bank. My plan was to use two 12V BattleBorn batteries in series, and they have a 100A continuous capacity. The 200A fuse had me concerned, but if it's only for surge draw the BBs can handle that for up to 30s.

Thanks for your answer, that 100% clears up my confusion!