100w System - Newbie - Diagram Design Review

[daz]

I'm not sure I follow you, Are you saying that, without RPD, a fuse (on both legs of the circuit) would not help protect a circuit from a reverse polarity connection?

That is correct.....
A fuse is just a piece of wire designed to 'blow' (eg break) when there is excessive current going through it. It does not differentiate in which direction the current is going. So a fuse provides over-current protection. A fuse is basically a non-resettable circuit-breaker.

A reverse protection diode on the order hand works differently. Diodes only allow current to flow in one direction (they oppose reverse current), which is why they are used for reverse polarity protection. A diode can only handle so much reverse current (and voltage), and if exceeded, will 'blow'. Diodes are not primarily designed for over-current protection, they are designed to only allow current to go in one direction.

So if you are just looking for over-current protection, then fuses are fine. If you want reverse polarity protection, then you will need to use a diode.

I hope the above helps show the difference between the two?

[ILFE]

Ok...I have weaved all this good info back into my ver 2.0 diagram...for your review

Open questions
1) MPPT controller amperage
2) Fuse amperage battery to Inverter

1) I should probably clarify myself on something here. I suggested a 30 ampere circuit breaker for the controller to battery for two reasons:

A. Circuit breakers are the same price for a given range of breaker sizes. You will usually pay the same price for a 9 amp and a 30 amp breaker.

B. I was thinking you may expand this system later, which had me considering a larger controller for your system in the first place. (It's nice to be able to add more batteries and solar modules to an existing controller and not having to replace it.)

If considering expanding your system lawter, I would go with something like a Rogue, a Midnite Kid, or another reputable controller. (Rogue (20a): $250 USD, Rogue (30a): $350 USD, Midnite Kid (30a): $285 USD) Supplier 1, Supplier 2, Supplier 3

If, however, you have no intentions of expanding your system later, then go with something like a Morningstar SunSaver 15 Amp MPPT Controller. Change the 30amp DC breaker accordingly - to 15 amperes. These controllers cost about $225 USD.

Regardless of which controller you go with, wire a circuit breaker in line that is rated the same size as the maximum output of the controller. Make sure the wire is sized accordingly as well. In the case of your most recent drawing, #10 is fine.

2) To fuse the inverter, you could go with a Blue Sea Fuse Block, which may be on your mind already? I would use a 150 ampere fuse.

Something I learned from a guy some time back was, just because a piece of hardware is rated for a given output continuously (he was talking about charge controllers and inverters), doesn't mean you should drive them to their maximum output day in and day out.

So, even if your battery bank could continuously provide power necessary to run your inverter at 1,000 watts, or just because your controller is rated at 30 amperes, doesn't mean you should run them at those limits every day.

Something to think about while you are building this.

[ILFE]

I hope the above helps show the difference between the two?

Yep. Thanks, Daz! I just never really thought about it before now, honestly. It has been a rare occasion that i have ever wired something up reversed polarity anyway. On the rare occasion that I did - I realized it pretty shortly thereafter. Hot dog roast, anyone?

EDIT: I mean, I have understood for a long time, regarding diodes and direction of current. I just never thought a fuse would NOT protect a DC current appliance if placed on the negative leg, without the aid of diodes.

[Jeepskate]

1) I should probably clarify myself on something here. I suggested a 30 ampere circuit breaker for the controller to battery for two reasons:

A. Circuit breakers are the same price for a given range of breaker sizes. You will usually pay the same price for a 9 amp and a 30 amp breaker.

B. I was thinking you may expand this system later, which had me considering a larger controller for your system in the first place. (It's nice to be able to add more batteries and solar modules to an existing controller and not having to replace it.)

If considering expanding your system lawter, I would go with something like a Rogue, a Midnite Kid, or another reputable controller. (Rogue (20a): $250 USD, Rogue (30a): $350 USD, Midnite Kid (30a): $285 USD) Supplier 1, Supplier 2, Supplier 3

If, however, you have no intentions of expanding your system later, then go with something like a Morningstar SunSaver 15 Amp MPPT Controller. Change the 30amp DC breaker accordingly - to 15 amperes. These controllers cost about $225 USD.

Regardless of which controller you go with, wire a circuit breaker in line that is rated the same size as the maximum output of the controller. Make sure the wire is sized accordingly as well. In the case of your most recent drawing, #10 is fine.

2) To fuse the inverter, you could go with a Blue Sea Fuse Block, which may be on your mind already? I would use a 150 ampere fuse.

Something I learned from a guy some time back was, just because a piece of hardware is rated for a given output continuously (he was talking about charge controllers and inverters), doesn't mean you should drive them to their maximum output day in and day out.

So, even if your battery bank could continuously provide power necessary to run your inverter at 1,000 watts, or just because your controller is rated at 30 amperes, doesn't mean you should run them at those limits every day.

Something to think about while you are building this.

Thanks livingincebu, that gets me going, appreciate all the help.