Critique my solar setup plan?

[dwh]

Hrmmm. I wonder if those are both made in the same factory. They have exactly the same battery settings and charge profiles. Literally, exactly the same.

I don't see any advantage to sending the one back and buying the other.

 

[dwh]

No. You don't downsize wire in the middle of a circuit.

If you start with #12, then you use #12 for the whole circuit and you protect that #12 with a 20a (or less) fuse (or breaker).

If you downsize part of the circuit to #14, then you have to downsize the fuse/breaker to protect #14.

 

[dwh]

12v sockets are usually rated 10a. So feeding two off a single #12 / 20a fuse is fine.

How much does the water pump draw?

 

[DaveInDenver]

No. You don't downsize wire in the middle of a circuit.

If you start with #12, then you use #12 for the whole circuit and you protect that #12 with a 20a (or less) fuse (or breaker).

If you downsize part of the circuit to #14, then you have to downsize the fuse/breaker to protect #14.

What dwh recommends is the only accepted safe practice. You could in theory branch smaller wires from a larger feeder as you distribute to loads. This topology would essentially be a bus with smaller conductors to the loads.

The problem arises during a fault. There's no way to predict where the current is going to flow if an individual load goes haywire. The only safe way to do 12ga -> 2 x 14ga -> 4 x 18ga would be something like a 20A at the 12ga feed, a 15A on each 14ga and an 8A on each 18ga. If you want only one fuse then you have to pick the lowest common denominator, which is a single 8A at the 12ga feed.

 

[mrsa111]

7.5, running the same guage wire to the loads shouldn't be a problem. So if an appliance, like say my pump has 16ga wires coming from it, and I'm runing that off 12ga cable along with another load, will that cause problems? Cause then the pumps 16ga wire is the weak point right?

 

[DaveInDenver]

7.5, running the same guage wire to the loads shouldn't be a problem. So if an appliance, like say my pump has 16ga wires coming from it, and I'm runing that off 12ga cable along with another load, will that cause problems? Cause then the pumps 16ga wire is the weak point right?

If you wire a 12ga directly to a 16ga on a load then the smaller wire is a potential hazard if there's no fuse ahead of it sized to protect it. You size current interruption when wiring branches to protect the wire and each load or device you connect will have internal protection if it needs it. So if you twist those 16ga flying wires to a 12ga you should put a fuse at the supplying end of the 12ga sized to protect the 16ga. There's nothing wrong with oversizing wire, the voltage drop will be slightly smaller, it'll be stronger, less likely to get kinked.

But just because it's 12ga doesn't mean you can automatically use a 20A fuse. You have to examine the complete circuit. This is why it common to have a terminal instead of leads, then you can wire end-to-end with your branch circuit, no potential funnels or short lengths of potential issues. Now assuming the device with the leads does have a fuse sized for 16ga your only risk is if the wire breaks right at the device and is left hanging, so it might only be a couple of inches of wire and the risk that it causes a problem is small.

 

[mrsa111]

Ok just looked at my water pump again, it does come with wires, but you can take them off their terminals. My lights are the hard part, I've got 4, maybe 5 led strips I want to use, and 4 individual circular led lights. I'd like to power all them with three different wire runs. But those wires seem to all be soldered in and using 18ga wire.

So for my pump and 12v socket, if the pump is 7.5a and the socket is 10, I should be fine running 14ga for everything and a 20a fuse right?

 

[DaveInDenver]

Fwiw, keep in mind fusing current of 18awg copper is about 80 amps.

Fusing current is to the melting of the copper (1,084°C), which is fine to know. Current carrying is based on the time to melt of the insulation. An 18 ga wire in 25°C still, ambient air will reach 75°C with 10 amps in about 60 seconds, so insulation type drive the charts. The correction factor for forced air gets 18 ga to about 15A for 60 seconds and bumping to 105°C insulation gets it to 12A in still air, 19A with forced air.

How you apply this is up to the designer. Having an exposed wire that hasn't fused might or might not be an issue, depends on if it can touch anything. How long you expect the fault current also factors in. A 20A fuse will blow with 80A in a few millisecond, so you'll never fuse a 18 ga wire, but will hold 20A forever so it will eventually melt through.

 

[dwh]

Ok just looked at my water pump again, it does come with wires, but you can take them off their terminals. My lights are the hard part, I've got 4, maybe 5 led strips I want to use, and 4 individual circular led lights. I'd like to power all them with three different wire runs. But those wires seem to all be soldered in and using 18ga wire.

So for my pump and 12v socket, if the pump is 7.5a and the socket is 10, I should be fine running 14ga for everything and a 20a fuse right?

Generally, you would use a 15a fuse to protect #14. 20a for #12.

Personally, for the water pump, I'd use #12 because I don't like small wires and I prefer to minimize voltage drop - especially to electric motors. But #14 would be fine as well. Then I would use a dedicated fuse slot for the water pump, and probably stick a 10a fuse in it. Best of both worlds.

When wiring buildings, it's common to have a bunch of various different loads hooked up to a single branch circuit / breaker.

And you can do it that way for vehicles, but I prefer splitting things up onto separate fuses in vehicles.


For the lights, 12a is a heavy enough load to possibly induce enough voltage drop to make the lights noticably a bit dim. Plus LEDs tend to run hot, and a lower voltage can make them run even hotter. Which is one of the most common reasons for LED failure.

So I'd go with #12 for the lights with a 20a fuse to protect the wire, and let the leads on the devices (LED fixtures) take care of themselves.



Also keep this in mind: When dealing with battery powered systems, as the state of charge of the battery goes down, the voltage of the circuit goes down. As the voltage goes down, the amperage goes up. As the amperage goes up, the voltage drop increases.

So your "12 amps" worth of LEDs might draw 12a...when the battery is full and the voltage is high. But as the voltage goes down over time, they'll draw more amps to provide the same watts. Which makes them run hotter, which is more watts being drawn. Sucking more watts, and at a higher amperage, will increase the voltage drop. Which will make the amps higher and the LEDs hotter thereby sucking more watts...it's a vicious circle that will end by eventually creating a super-giant black hole which consumes the galaxy.

Okay...not quite that bad.

But still, it happens on low-voltage battery powered electrical systems and can be mostly avoided by simply oversizing the supply wire.

 

[rayra]

Recommending multiple inverters, different sizes, try to use whichever is most appropriate for your load. Less energy lost as heat. And the whole 'one is none, two is one, three is for me' thing. You need to have redundancy.

 

[mrsa111]

had to put off the electrical while i finished up the rest of the build, but now i'm getting back into it.
Here's my basic wiring diagram, just want to see if i have the right idea.

these are my questions..

1) Is there any reason not to run the charge controller through an accessory circuit in the blue sea fuse block? its a victron 50 amp mppt, so run it with a 50 amp fuse?

2) fuse locations, you want the fuses either coming from or very close to the battery right? then switches after that. After writing that diagram im now realizing that fuse between the charge controller and fuse block is probably unnecessary? since it'll be fused through the accessory circuit?

3) I've seen other wiring diagrams where people will wire the fuse block through the charge controller rather than straight from the battery, any reason for that? is my thinking wrong? with my charge controller I dont have "load" hook ups, only for the panels and battery.

4) grounding, Is it necessary to ground to the van chassis? I remember hearing somewhere that there was another way to run the ground, through the charge controller or something?

5) any input on sizing fuses? Im thinking 50 amp for the charge controller, 100 amp for the battery between both the inverter and the fuse block.

 

[mrsa111]

Nothing wrong with connecting your MPPT output to one of the BlueSea fuses.
A minor concern, if your battery to Bluesea were disconnected, either by switch or blown fuse.
Solar will 'backfeed' power to whatever else is connected to BlueSea.

Ultimately fuses or your favourite OCPD protects conductors and devices. Perhaps ”current path” is better phrase.
Your MPPT will only output 50A if you have at least 50A worth of solar modules.
Regardless, dont fit fuses what exceed ampacity of a current path.

”Ground”
While its not needed if all circuits have appropriate negative conductor. Unless a special situation makes good reason not to, I think grounding negative always good practice.

Btw, many solar controllers are intended to be positive grounded.
If yours is such. It will still work. BUT, Dont connect ANYTHING of it to ground except its battery negative.

What do you mean by backfeed? as in the solar power will be powering my appliances directly? anything wrong with that?

Another thing, that blue sea fuse block is only rated to 30 amps per circuit, guessing that wont work with my charge controller? its the victron 100/50, so guessing i'd need to fuse it to 50?

when I'm joining multiple appliances off one wire run, for example, 4 led lights off one wire run, or an led strip and 12v outlet, etc. whats the best way to splice the wires together? twist connectors? just strip the shielding and twist together then cover with heat shrink?

 

[dwh]

had to put off the electrical while i finished up the rest of the build, but now i'm getting back into it.
Here's my basic wiring diagram, just want to see if i have the right idea.

these are my questions..

1) Is there any reason not to run the charge controller through an accessory circuit in the blue sea fuse block? its a victron 50 amp mppt, so run it with a 50 amp fuse?

No problem. I've got a 30a Victron that feeds into the fuse block via 30a fuse. Just make sure your fuse block is rated to handle however many amps.

Doesn't really matter what the max rating of the charge controller is - fuses protect the wire. My charge controller is rated 30a max. But I've only got 300w of solar connected to it. 300w ÷ 11v = 27a. So I used #10 wire, rated 30a and a 30a fuse to protect the 30a wire.

But I didn't do that because the charge controller is rated 30a. I did it because #12 (rated at 20a) wasn't big enough to handle the max expected load of 27a, and the next size wire was #10.

Size the wire to handle the load, size the fuse to protect the wire.

2) fuse locations, you want the fuses either coming from or very close to the battery right?

Since the fuse protects the wire, you normally want the fuse as close to the source as possible, to protect the full length of the wire. The fuse won't protect the wire from a short between the source and the fuse.

then switches after that. After writing that diagram im now realizing that fuse between the charge controller and fuse block is probably unnecessary? since it'll be fused through the accessory circuit?

Technically...there is a power source at both ends of the wire, so you should have a fuse at each end to protect the wire from either power source. But in the real world...

Just depends. I don't have enough wire between my solar panel and charge controller to really worry about it. Besides, to put a fuse at the solar end, I would have had to cut the wire coming out of the solar panel...and I didn't want to. So my setup has no fuse at the solar panel.

If I was running 50' of wire it might have been a different story.

3) I've seen other wiring diagrams where people will wire the fuse block through the charge controller rather than straight from the battery, any reason for that? is my thinking wrong? with my charge controller I dont have "load" hook ups, only for the panels and battery.

The load terminals (if the controller has them) are usually protected by a low-voltage-disconnect (LVD) that will keep the battery from being fully drained. The load terminals are also usually limited to like 10a, so it's not a good way to feed a fuse block.

Fuse block connected to the battery is the best way.

4) grounding, Is it necessary to ground to the van chassis? I remember hearing somewhere that there was another way to run the ground, through the charge controller or something?

If you are charging the aux battery from the alternator, then that battery will be grounded to the chassis. So the fuse block connected to that battery will also. As will the OUTPUT side of the charge controller.

DO NOT ground the input side of the controller (wires from solar panel) to the chassis. Let that be separate.

5) any input on sizing fuses? Im thinking 50 amp for the charge controller, 100 amp for the battery between both the inverter and the fuse block.

Whatever the amp rating of the wire is - that's what size fuse you use.

 

[dwh]

Best way to make connections on branch circuits is good quality crimp connectors covered by heat-shrink.

 

[mrsa111]

No problem. I've got a 30a Victron that feeds into the fuse block via 30a fuse. Just make sure your fuse block is rated to handle however many amps.

Doesn't really matter what the max rating of the charge controller is - fuses protect the wire. My charge controller is rated 30a max. But I've only got 300w of solar connected to it. 300w ÷ 11v = 27a. So I used #10 wire, rated 30a and a 30a fuse to protect the 30a wire.

But I didn't do that because the charge controller is rated 30a. I did it because #12 (rated at 20a) wasn't big enough to handle the max expected load of 27a, and the next size wire was #10.

Size the wire to handle the load, size the fuse to protect the wire.




Since the fuse protects the wire, you normally want the fuse as close to the source as possible, to protect the full length of the wire. The fuse won't protect the wire from a short between the source and the fuse.




Technically...there is a power source at both ends of the wire, so you should have a fuse at each end to protect the wire from either power source. But in the real world...

Just depends. I don't have enough wire between my solar panel and charge controller to really worry about it. Besides, to put a fuse at the solar end, I would have had to cut the wire coming out of the solar panel...and I didn't want to. So my setup has no fuse at the solar panel.

If I was running 50' of wire it might have been a different story.




The load terminals (if the controller has them) are usually protected by a low-voltage-disconnect (LVD) that will keep the battery from being fully drained. The load terminals are also usually limited to like 10a, so it's not a good way to feed a fuse block.

Fuse block connected to the battery is the best way.




If you are charging the aux battery from the alternator, then that battery will be grounded to the chassis. So the fuse block connected to that battery will also. As will the OUTPUT side of the charge controller.

DO NOT ground the input side of the controller (wires from solar panel) to the chassis. Let that be separate.




Whatever the amp rating of the wire is - that's what size fuse you use.

Thanks, I need to get it through my head to fuse for the wire size! I'm thinking for everything between the charge controller, fuse block, battery and inverter, i'll use 4awg. I have a lot of it so it'd be nice if I could use it for all those. with the ground being larger, #2?

Since i'm going to need a fuse going from the battery to the inverter, and from the battery to the fuse block, and both those wires will be sized the same, can I just run a single fuse straight off the battery, then two wires from there?