Some help choosing fuses please. (1 Viewer)

[gillsimo]

Try as I might my ageing brain just will not, now, grasp basic electrical theory, even though, as an electronics engineer back in the day, I had a perfect knowledge /understanding of it.....senility approaches I guess!
Anyhow...I'm hoping someone here, with grey matter still to spare, can apply the theory & then simply give me the figures?

I have 3 x 170W panels in series connected to a Renogy 40A Controller. This is connected to 4 x 180Ah/12v batteries in parallel, to which is connected a Renogy 3000W Inverter.
I require a fuse/breaker for all three connections but haven't a scooby as to what values/types.
If anyone could help out & perhaps offer a link to a half decent example t'would be very much appreciated thank you.
Gill

 

[autorouter]

A 3000W inverter will pull 250A from the 12V batteries, so you will need a fuse bigger than that, maybe 300A. I would use a MegaFuse and holder for this.

The solar is the exact opposite, with three panels in series. Look at the Short Circuit amps for the 170W panel, probably about 8A, so a 10A or 15A fuse is suitable. If you were wiring the panels in parallel, that would be about 25A, so a 30A or 40A would be suitable.

On the Renogy solar controller output wire to the battery, I would use a 50A fuse.

A convenient connection method is to use a fuse block that mounts near the battery, that takes one big Mega fuse and a few smaller Midi fuses, like this. You could wire all your existing connections to one of the Midi fuses.

Mega & Midi Fuse Power Distribution Box

Compact power distribution & fuse box that distributes power theough a single mega link fuse into 4 midi or strip link fuses.

www.12voltplanet.co.uk

With four big 12V batteries and a very high amps draw from the inverter, it would be a good idea to use a positive and negative busbar also, and run equal length wire links from the busbars to the battery terminals. Using that method ensures that the voltage drops to all the batteries are equal, so all the batteries are equally loaded and none of them are excessively strained.

https://www.12voltplanet.co.uk/vte-...tive-distribution-blockbusbar-with-cover.html

https://www.12voltplanet.co.uk/vte-...tive-distribution-blockbusbar-with-cover.html

 

[Figaro]

 

[IRHP]

Shouldn't need a fuse between solar panels and the controller as the wiring should be rated for the maximum current the panels can provide but a breaker is a good idea for maintenance purposes.

 

[gillsimo]

Thank you very much, exactly what I required.
Apologies for not responding sooner....been a bit unwell of late.

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[Raul]

Shouldn't need a fuse between solar panels and the controller as the wiring should be rated for the maximum current the panels can provide but a breaker is a good idea for maintenance purposes.

You need to fuse for 3 or more in parallel. Even two parallel is good to fuse. On series no, unless its a call for long run of cable to be protected on route to the controller; in this case use system fuse data of the panel sticker. But if two series paralleled then yes, fuse individual string.
If a panel develops a fault and becomes a load, in case of 3 parallel, the two healthy panels will dump all the power into the faulty one. So in parallel all panels should be fused before they meet together. The fuse rating should be close to ISC rating of the panel, and the ultra fast type gPV fuse. No other fuse type will blow on time to save the damaged panel catch fire.
My two parallel panels on the roof, are fused at 8A each with 10x30 gPV fuses. The panels ISC is 8A. Then, together connected to the controller. From controller output fused again at controller rating output.

Most common fault on panels, is the rear connection box, sometimes blows a shotky, or loose connection melts the box. Some are fully filled with putting compound and fair better. Another fault is snail trail developing brow spots. If this spot goes through enough cycles to melt the eva sheet at the back, opens the door to moisture and corrosion. Perfect for short or short to frame.