Switch or fuse on Solar input

[Alanf1]

I have a solar install which currently consists of a 150W panel going into a Votronic MPP350 controller.

I will be adding an equivalent 100W panel to the setup in the near future.

 

I want to include a fuse or switch after the cables enter the van roof, but which should I use and should I have one on both the positive and negative cables or will one on the positive be sufficient?

 

Something along these lines:

 

https://www.ebay.co.uk/itm/20AMP-Manual-Reset-Switch-Circuit-Breaker-12V-24V-Inline-Auto-Waterproof/201830174429?epid=2272530826&hash=item2efe040edd:g:diwAAOSwp7tacDwb

 

or

 

https://www.ebay.co.uk/itm/30-AMP-MIDI-FUSE-ORANGE-MIDI-STRIP-LINK-FUSE-HOLDER-CAR-AUTO-HEAVY-DUTY-30A/201688958022?hash=item2ef5994446:m:mBOdtqM7A9uoTBar5ZIcGEA

 

Is 30 amp the correct size or would 20 be sufficient?

I'm using 6mm^2 solar cable

[Alanf1]

After doing some more reading I'm thinking that 20 amp fuse/breaker would be enough on the panel side.

The panel output shouldn't exceed 15 amps and the cable is rated quite a bit more than that.

I currently have 30 amp fuses between the controller and battery.

 

I just want to make sure that my assumptions are correct?

 

I'm still not sure whether just the positive or both cables should have the split but will probably do both for piece of mind.

[Charles]

Shouldn't need fusing as such, the cable down from the panel should be big enough to handle the full output current of the panels, and the controller blade fuse is protecting the battery side of the circuit. But fit one fuse in the positive cable so the controller can be isolated from the Solar panel by pulling the fuse.

[aandncaravan]

The work we have done with these 'trip' switches is not huge, but they proved to be erratic on the current at which they trip. For example a 20amp unit might trigger at 20 amps one time and 30 amps the next. None of the ones we sourced seem well made or constructed to tight tolerances.

 

The fuse holders you list are fine but a bit of a pain to remove the fuse for maintenance/isolation. They also tend to have a more restrictive fuse range at the lower end.

 

We would suggest an ordinary Standard Blade fuse would be the easiest option with a selection of fuses in increments of 5 amps that are easy to source.

A second suggestion would be a Maxi Fuse holder if the cabling is thick.

Just fit the fusing in the Positive cable.

 

 

 

 

 

[Alanf1]

Thanks for the advice.

 

I'll look into the maxi fuse holders - although I think I have a couple of the midis available, but like you say, not that easy to isolate with those.

 

Thanks for all the replies :-)

[sshortcircuit]

I currently have 30 amp fuses between the controller and battery. " and the rating of that cable?

 

You will be lucky in uk to get 15a for long enough

[Robbo]

The 20amp manual reset switch mentioned by the OP does seem to have a rather large input/output size.

 

Another website selling the same product (incarproducts), quotes suitable cable sizes between 8mm sq to 21mm sq (8 to 4 AWG).

 

This isn't an insurmountable problem as the 6mm sq solar cable could be folded over (doubled) or terminated with a bullet connector to increase the size.

 

The manual reset switch does look like a neat solution for isolating the solar panels, providing it's reliable. Members on another forum have used this device on the solar input cable without any reported problems.