FUSE SIZE

[Johnnny]

Hi have just ordered CTEKd250se B2b to replace my vsr.
It is 20a so can anyone tell me what size fuses should use inline.
need to replace as think will be bigger than vsr fuses
thanks

 

[Spriddler]

In short, the fuse must be of a lower rating than the current-carrying capability of the wiring that it's protecting.

 

[gerry mcg]

^yip
Does the B2B installation manual state a fuse reccomendation?

Fuses are to protect the cable from melting, so fuse < cable Rating.
E.g 16mm2 cable is rated at 110A my votronic 1212-50 B2B outputs 50A, votronic recommends a 80A (midi) fuse.

This will give you an idea of cable ratings
Cable diameter is only one part of the equation. Resistance is another. See this calculator for cable sizing.

And this fusing guide

 

[autorouter]

For a 20A current, it's best to use a fuse at least 25 to 30% higher, and the next value available is 30A. You then need to ensure your cables are capable of taking 30A without overheating.

When choosing a cable, you need to consider safety (heating) and voltage drop. Usually the cable is selected for a maximum voltage drop of 3% or less. Such a cable will be well within the safety limits for overheating. The link in gerry mcg's post will give you the cross-sectional area of the cable required, if you tell it the length of the cable. Probably 10mm2, but maybe 6mm2 if the distance is very short. It's quite likely the existing cables are adequate.

 

[Johnnny]

Thanks sorry for delay. I intend to use cable which runs from starter to vsr at back van beside liesure battery. Its 16mm sq and 5m length. Hopefully just a straight swap over replacing vsr with ctek b2b. Instructions also say 30a fuses so hoping to fit this week
Thanks

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