Fuse placement

[Aussiemike]

Hi Guys,
Bit new to this game but have been studying for a few weeks now online.
At my age not an easy thing.
I would like to describe a layout and ask if I am right in my assumption.
Got to get it right as it is going in a thatched roof cottage on the beach in Northern Tanzania and a fire scares the s**t out of me.

I have 2 x 150 Amp 12v batteries in series giving me 24 volts and 150 Amps.
Will add another two at a later date.
The feed goes into a 80 Amp 24 volt Charge controller then to a 3000w pure sine wave inverter.
The inverter powers a 200 watt fridge/freezer.
Am I correct in saying that the current coming from the battery is 200w/240v=8.33 amps plus the 1 amp for the inverter total 9.3 Amps.?
Wire size is 6 gauge
Therefore I should fuse the line from the CC to the inverter with a 20 Amp fuse?
If that is not correct where do I put the fuse?

Solor Panel -------- Charge Controler

Charge Controler ------ Battery

Charge Controler ---------- Inverter

Inverter ---------- Fridge

TIA
Aussiemike

[SunEagle]

First off you do not wire the charge controller to the inverter.

The system should be wired; Solar panels ... charge controller .... batteries ... inverter .... fridge.

Now the wire from the 80 amp charge controller to the batteries should have an 80 amp fuse and be rated for more than 80 amps.

The wire from the 24volt batteries to the 3000 watt inverter should be rated for (3000w / 24v = 125a) at least 125 amps and the wire should be rated for more than that.

The wire from the 240volt inverter to the fridge should be rated for whatever the fridge nameplate states. The inverter should have an internal fuse for the 240volt outlet.

The fuse and wire size between the panel and the charge controller will depend on; the nameplate rating of the panels, the number of panels, how they are wired, how far they are from the charge controller. Since you did not supply us with this information it would be hard to provide you with the fuse or wire size.

[Aussiemike]

I cannot thank you enough for this information.
For me to comprehend it completely may I ask another question?
I am upgrading from a simple 12v system.
On that system on the CC there are 3 pairs of terminals.
1 battery
2 panels
3 load.
Q. Is the inverter not a load and therefore should be connected there?

Secondly.
I have read in many places that I do not need to fuse between panels and controller.
Have I misunderstood?
If so the info I did not give you is
2x12v panels at 200w each in series 50ft from the controller with 6 gauge wire.

Cheers
Mike

[littleharbor]

The load output on your CC is for controlling small loads such as lighting. It will shut down the load if the battery voltage gets dangerously low to prevent damage to the battery. The load output terminals are usually limited to the CC amp rating , if not less. Your inverter will be drawing WAY MORE amperage in any moderate use scenario. Keep in mind that , for example a 10 amp load on a 12 volt inverter is going to ask 100 amps+ from your batteries. Not something you want to be drawing through your controller.

You don't need to fuse solar to CC until you get to 3 panels or 3 strings of panels as the potential amperage of two panels or strings is low enough to not be able to harm the panels. In this event, (3 or more)you need to fuse each individual panel or string of panels. That being said it is still nice to have a circuit breaker between panels and CC as well as from CC to Batteries for system control and maintenance.

[SunEagle]

The answers that littleharbor gave you are correct.

The "load" terminals are not to be used by your inverter. They are just for very small wattage lighting loads. The inverter should be wired directly to positive and negative battery terminals with a fuse protecting that wire.

You do not need to fuse the wiring between your solar panels and the charge controller if you do not have more than 2 panels or strings wired in parallel. Since you have 2 x 200watt panels wired in series you meet that requirement but having a way to disconnect the panels from the charger is a nice feature. You can use a circuit breaker rated at the Isc (short circuit current rating) of the panel for that.

[Aussiemike]

I remember a song by Harry Belafonte many years ago with the words....
"It was clear as mud but it covered the ground."
Starting to understand what he meant.
You mention preventing damage to the battery.
But isn't that what will happen if you run the inverter straight from the battery?
All I am trying to run is a 185 watt (freezer turned into a fridge) through a 24v inverter.
The CC is 80 Amp. Isn't that big enough?
FYI I am trying to implement the following

https://mtbest.net/chest_fridge.html

This Australian professor has claims he runs a fridge for around $3 a year.
His logic is sound and I have bought the electronic box from him.
I am in no way associated with him.
Cheers
Mike

[Aussiemike]

Thanks SunEagle. Your post came through after I had sent mine. Really appreciate your guys help in this.
Here in Kenya we use anything we can find to do most jobs. Between my solar panels and my CC I was just using the plugs that you find on the cables on a UPS.
Do I hear laughter or are you just thinking "Dumb Aussie"

[SunEagle]

Thanks SunEagle. Your post came through after I had sent mine. Really appreciate your guys help in this.
Here in Kenya we use anything we can find to do most jobs. Between my solar panels and my CC I was just using the plugs that you find on the cables on a UPS.
Do I hear laughter or are you just thinking "Dumb Aussie"

I never think someone is dumb if they have to ask a question. I always want to make sure someone did something right to stay safe when it comes to electricity.

I have had too many friends and co-workers get hurt because they either became complacent or did stupid things when it came to electricity. Electricity is something that will strike you like a snake when you aren't looking and in most cases kill you.

Remember the CC takes the DC voltage from the solar panel and charges the DC battery. The inverter changes the battery DC voltage to the freezer AC voltage.

Any voltage above 50v and any current above a few Milli-amps can kill you. A battery might only delivery voltages below 50v but it can delivery a lot of amps so it can easily cause a fire and even kill in the right circumstances. Stay safe my friend.