Trying to install a new panel and very frustrated

[Jd1]

Originally Posted by Cthoops

Thank you. Fusing at 30 (or 40) does make more sense than 125 now that you point it out.

Actually that is incorrect and you were correct to begin with.

A fuse protects the wire after the fuse. A #6 wire is rated at 120A. You can run 120A through that wire until the cows come home and nothing bad would happen. You can run more short duration current through it (as in surge current) and nothing bad will happen.
Fuse size has nothing to do with the length of the wire run. You could run a mile of #6 wire with a 120A fuse and all will be well as far as the fuse and the wire is concerned.
Now looking at whatever you hook up after that mile is quite a different matter. That is why you have 10% voltage drop tables and 3% voltage drop tables. That is the ONLY reason why you would want bigger cable.
You generally would not work with a 10% drop table .... it is too much of a drop for pretty much any electronic device. ... but you could use it if generally you only expect rare usage of the full power or you know that your devices won't care.

Anyway, run your 100 or a 120A fuse and be happy. All branch circuits off that main feeder are of course fused separately depending on the wire used in that branch circuit.

[fdr14127]

I have recently rewired my panels and here is what I used: (minus the A/C components which were an upgrade to a DLT, not germain to this thread).

Battery Isolation relay: Here is where the custom battery cables connect with the appropriate size terminals for the total load. Of course you fused them at the top of the battery posts eh? (Marine Battery Terminal Fuses)

Blue Sea Systems SI-ACR Automatic Charging Relay with Start Isolation

Main 12v DC switch:
Blue Sea Systems Dual Battery Bank Management Panel

Right now you are here.......!
12v DC panel:
You already have it, use it.

What you should do now is go to Blue Seas site and download the install instructions for the various devices and read the wiring diagrams, This will answer your questions on how to wire this system. After installation of the devices order up custom battery cables (I use a shop in Annapolis, but there are others) and that will make your install look neat, orderly and professional. All else fails call the support folks at Blue Seas and ask questions. You will find them polite, helpful, and open minded about various solutions.....of course Google is always your friend.

[Zil]

I have that BlueSea fuse panel with the #10 connection. It is listed at the maxium of 100 amps. I would not operate at 100%. For mine, I have 15 feet of 4AWG with #10 lugs. I have it fused for 100 Amps at the battery terminal. But my circuits will not be 100 amps even if all on together. My 15 ft 4awg can carry 50 amps with 3%ish voltage drop.

[DeepFrz]

Basic Marine Electrical - Part 1 of 6 - Cruisers & Sailing Forums

[rwidman]

Originally Posted by hellosailor

There's never a quantum physicist around when you need one.

Actually I was told decades ago that the conventional "electrons flowing" business is totally wrong 1950's physics. And that by the 60's they had figured out that electrons don't flow from the negative terminal, but "electron acceptance holes" or some such thing flow from the positive terminal...I don't even try to remember what the deal is, but just that 'electricity' flows the opposite of the way we were all taught (and still are taught) in school. Unless you're in an EE program or working on the Large Hadron Collider.

You could take a "round trip length" chart, cut all the numbers in half, and make a "one way length" chart out of it. Sure. Doesn't matter, just READ THE CHART and make sure to apply apples to apples.

(I don't care what is flowing which way in those wires, I just want the light bulbs to work.)

Regardless of electrons or "holes", there has to be a complete circuit for current to flow. In this case, it's from the battery to the panel, through whatever loads are connected and back to the battery. That's why we measure the complete circuit.

[sainted]

So. Where are your battery switch(ed)? Generally, the gauge of the wire running from the battery switch to the panel need only be #6 or so because the battery switch is somewhat close to the panel. The cables coming from the batteries to the switch are large enough to support engine starting currents, so 1/0 or so for a sail boat with a 4 cylinder, 2.0 liter motor. I mean, we're not talking 6 liter Cats here, right?

If your battery switches are indeed 25' from your panel, then I'd recommend #2 wire from the switch to a bus bar right behind the panel and #6 wire from the bus bar to the panel. You'll also need a negative terminal bus mounted on the bulkhead behind the panel. You can run a #2 cable right to that bus. Don't use whatever negative bus might be located on the panel. Doing so will make the bundle of cables going to the panel too unwieldy. See the attached (l hope) photo.

Don't forget an "un switched" facility for your 24/7 loads such as bilge pumps or radio memories. Of course, these services need to be properly breakered, to.

If you want more help, pm me.

Scott
Marine electrician

[mitiempo]

Originally Posted by sainted

So. Where are your battery switch(ed)? Generally, the gauge of the wire running from the battery switch to the panel need only be #6 or so because the battery switch is somewhat close to the panel. The cables coming from the batteries to the switch are large enough to support engine starting currents, so 1/0 or so for a sail boat with a 4 cylinder, 2.0 liter motor. I mean, we're not talking 6 liter Cats here, right?

If your battery switches are indeed 25' from your panel, then I'd recommend #2 wire from the switch to a bus bar right behind the panel and #6 wire from the bus bar to the panel. You'll also need a negative terminal bus mounted on the bulkhead behind the panel. You can run a #2 cable right to that bus. Don't use whatever negative bus might be located on the panel. Doing so will make the bundle of cables going to the panel too unwieldy. See the attached (l hope) photo.

Don't forget an "un switched" facility for your 24/7 loads such as bilge pumps or radio memories. Of course, these services need to be properly breakered, to.

If you want more help, pm me.

Scott
Marine electrician

I agree with this post.

Is your battery switch really 25' from the panel on a 30' boat?

I also like to keep all the negatives on a bus behind any panel I install. The only negative I run to the panel is for any indicator lights it has.

[jhulmer]

Another yes to what Sainted suggested.
I am in the middle of rewireing a Blue Sea 100amp panel as well.

I have run 2/0 to my batt switches from the batteries and 2 awg to my panel 8 feet away from the switch. I could have used 4 awg but I decided to use bigger wire for future needs. Having had to change out to bigger wire on my previous boat, I'm ahead of the game now.

I used 2/0 to batt 1 switch, batt 2 switch and the combine batt switch. In the event I need to combine all batteries for engine starting.

Yes to bring the bigger wire to a bus behind the panel and then run smaller wire to the panel main if necessary. However, I was able to connect the 2awg straight to the panel with no problem. yes you can get batt lugs for 2awg with 1/4"and #10 hole. (have a shunt with 1/4 studs)

Appropriate fuses per ABYC in all cables to protect the wire and I included a 300amp on the starter cable.
After the circuit breakers (which protect the wire to the equipment bus) I have appropriate fuses to protect the equipment. For example: sailing Instruments is a 10amp breaker with 14 ga wire run to a small 6 fuse Blue Sea fuse block and fused appropriate to each instrument on the instrument cluster.

The breaker to say the AutoPilot can be sized specifically for that equipment and the appropriate wire run direct.

picture of my progress so far (I am farther along then this I need an updated pic):

[smac999]

2awg to a panel is not oversized. Lots are 2/0.

But it doesn't need to be full size the whole way. Run 2awg to the panel cupboard to a power post etc. Then run a short smaller cable from post to main. Big enough for the breaker size. Voltage drop is nelgible in a 2' jumper wire

[Terra Nova]

Use the #2 cable with an appropriately sized terminal and add a very short solid bus bar extender if necessary to connect it.