Adding a 12v Blue Sea Fuse Block

SCBrian · 05-12-2013, 06:59 PM

In an effort to increase my fridge run time I'm adding a 12v panel in the van. I have the Edgestar Fridge that is normally run through the inverter. I tested a couple of weeks ago and I got roughly a 30 hour run time with my current set up. This has always been fine for our use because at the most in the past we've only run the inverter 12 hours or so and everything's been fine. Realizing we may have some extended power issues (not being able to plug in, not having solar) I was trying to come up with a solution for extended battery run times for the fridge. Talking with another friend about my set up I realized the fridge was AC/DC and if I added a DC plug for the fridge I could possibly extend my fridge run time without having to use the inverter.

Couple of questions:

1. Can I ground the new 12v fuse panel directly to the inverter without harming anything so that they would share a ground. For clarity the panel would be grounded directly to the inverter. I'm asking because that's the only ground that I have inside of the cabinet where I'm mounting the 12v panel. I could ground the panel separately with a little extra work but I'm running out of time before our trip. Here is the fuse panel: http://www.amazon.com/Blue-Sea-Systems- ... s=blue+sea

2. Both house batteries have 100amp fuses before the inverter. They are wired to a power bar before reaching the inverter http://www.amazon.com/Blue-Sea-PowerBar ... s=blue+sea. I have room to come directly off of the power bar to the fuse panel. That would mean that the inverter and the fuse panel would share a common positive. The individual circuits coming out of the new panel would be fused but between the inverter and the fuse panel would not be. Is this a problem?

3. Wire size. I was planning on 8 or 10 gauge for powering the new fuse panel and also the ground. Comments?

I basically have this week to get the new fuse panel and the new 12v socket installed so I can at least test before leaving. Thanks in advance for the help!

**daveb** · 05-13-2013, 01:56 AM

What is the new fuse panel going to run other than the fridge?

I'm not seeing anything that pops out as a problem. At least on my setup the 4/O cables running from the battery bank run to the inverter and piggyback off the inverter lug then they go to my fuse block so it sounds like you're doing the same. SMB did use a 2STR ground as the tie to the inverter/fuse block/vehicle ground. The positive is the same or #4STR if I recall. But that fuse block runs everything for the house 12 v system.

SCBrian · 05-13-2013, 04:21 AM

Quote:

Originally Posted by daveb

What is the new fuse panel going to run other than the fridge?

I'm not seeing anything that pops out as a problem. At least on my setup the 4/O cables running from the battery bank run to the inverter and piggyback off the inverter lug then they go to my fuse block so it sounds like you're doing the same. SMB did use a 2STR ground as the tie to the inverter/fuse block/vehicle ground. The positive is the same or #4STR if I recall. But that fuse block runs everything for the house 12 v system.

Currently I have no other plans for 12v. Maybe some additional lights in the future, also possibly other 12v plug ins. So far Ive kept everything simple. My main cables from the house batteries to the power bar are 2/0 if I remember correctly. I just don't want to tie the grounds together on inverter lug for fear of frying the inverter or vice versa. Right now the new fuse panel is overkill because originally I was going to use an inline fuse holder for the 12v socket.

**daveb** · 05-13-2013, 08:58 AM

I wouldn't want any 12v source having a isolated ground on the van. All the grounds should be tied together and connected to the chassis. But even though mine is set up that way you might want to check with who made the inverter. There are some circumstances that the ground could be fused with a heavy amp fuse (300A) but for the most part I don't think it's absolutely needed.

charlie56 · 05-14-2013, 09:24 AM

Maybe I am missing something but why bother with the fuse block? If you are not really going to use it for anything else just run a new fused circuit (+ and -) direct from the battery. You wil have the least voltage drop that way. There is a calculator on the bluesea website for sizing the conductors based upon load, wire size, and length.

I think using 8 or 10 ga wire as a feeder is not the right thing to do. Sooner or later you or someone else will want to tap into that fuse block with a larger load. Unless that feeder is fused it might leed to a dangerous situation. (I just installed a blue sea fuse block and used #6 as a feeder with a 40amp fuse on the feeder before the fuse block.)

Hope that helps...

Scalf77 · 05-14-2013, 11:27 AM

I agree, if your going to put on the fuse block you still need a fuse or breaker for the feeder from your bus bar to the fuse block. If you are going to add additional circuits later, you should chose wire and fuse for that now. I don't see anything wrong with using the ground connector on the inverter.

-greg

SCBrian · 05-14-2013, 02:42 PM

Thanks guys.....The run for the fuse block is only a foot or two at the most. I read Blue Sea packaging and I thought that #8 or 10 was sufficient (I don't remember what I ended up buying)(I think I bought #10 for the 12v socket and #8 for the fuse block). If I was running from under the hood then I would agree. It's not like I know anything anyway. I bought some supplies yesterday but I didn't pick up a fuse holder for before the fuse block. I'm on the way home in a few minutes to lay everything out and take inventory.

***I bought #6 for both the positive and negative feeds***

**daveb** · 05-14-2013, 03:53 PM

Well the fuse block itself has an amperage limit on it as well. No sense running heavy wire to something that can't output what you're inputting. The fuse block will be the weak link in that case. You'll have to factor that in for sure.

rockbender · 05-14-2013, 05:19 PM

These photos were graciously highjacked from Madspaniard on the Samba - I used his work for reference when building my electrical system. Mine is similar by function, but not nearly as pretty as his:

You can see that the power is piggybacked off of the power going to the inverter; however, the inverter and fuse block have separate circuit breakers.

Scalf77 · 05-14-2013, 06:22 PM

The big Key is to have the fuse or circuit breaker from the bus bar to the fuse block match the size of the wire you are using. Blue Sea Systems has a nice calculator on their web site, you can also download a version for I-phone and android.
I think the fuse panel you showed is actually capable of 100 amps. I can't imagine that you would have that kind of need, when choosing wire size, you should also check the temperature rating of the wire. The Blue Sea App helps you choose fuse or breaker also.

http://circuitwizard.bluesea.com/

Greg