Fusing to busbar

[Tim22]

I am re doing some wiring and want to install a + bus to connect the solar controller, battery charger, and inverter to the house bank. These need to be fused at the busbar. I would like to avoid using short jumpers to connect the fuses to the busbar. Instead, I would like to connect the fuses directly to the busbar. I came across this blog post Fabricating a DIY ANL Fuse Block which shows a similar installation and I would be interested In knowing if this is an acceptable solution.

Thanks
Tim

 

[Ron20324]

What kind of fuse and amperage?

 

[dlochner]

I am re doing some wiring and want to install a + bus to connect the solar controller, battery charger, and inverter to the house bank. These need to be fused at the busbar. I would like to avoid using short jumpers to connect the fuses to the busbar. Instead, I would like to connect the fuses directly to the busbar. I came across this blog post Fabricating a DIY ANL Fuse Block which shows a similar installation and I would be interested In knowing if this is an acceptable solution.

Thanks
Tim

There are 2 easier solutions.

Blue Sea makes a terminal bar the uses Marine Battery Terminal Fuses.

MRBF Surface Mount Fuse Block - Common Source - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

Or build one using a piece of 5/16" x 1" copper bar and ANL fuse holders.

 

[Ward H]

I did something very similar as @dlochner. Lined up some ANL holders and connected them with a copper bar custom drilled.

 

[Tim22]

I looked at the Blue Sea MRBF fuse block but rejected it as I don’t think it has the capacity. The charger and solar controller are relatively low fuse at 25 & 50 Amps. The 1800w inverter, however, suggests fusing at 300A.

I like the idea of bussing the ANL fuse holders. Is there a formula to calculate the size required? I was looking at the 600A Blue Sea Busbar so it would need to have the same capacity.

Thanks
Tim

 

[dlochner]

I looked at the Blue Sea MRBF fuse block but rejected it as I don’t think it has the capacity. The charger and solar controller are relatively low fuse at 25 & 50 Amps. The 1800w inverter, however, suggests fusing at 300A.

I like the idea of bussing the ANL fuse holders. Is there a formula to calculate the size required? I was looking at the 600A Blue Sea Busbar so it would need to have the same capacity.

Thanks
Tim

I borrowed the copper busbar idea from MaineSail. Somewhere on his site or in his forum there was a photo of one similar to mine. I asked him about the size.

If the battery cable and the Inverter cable are on the same fuse holder you'll be fine because it is a direct connections. This is why Power Studs are not rated. On my bus bar the battery cable connects at the right end and the main feed to the panel and windlass are on the right side. The cables are then arranged in order of current draw, the highest draw closest to the main feed, the lowest draw to the far left (feed to ACR and start battery).

 

[Tim22]

If I can connect the Inverter to the MRBF common terminal with an ANL fuse (see attached drawing) then the MRBF bus would probably be the easiest solution. I would put the ANL fuse between a blue sea power post connector and the busbar common terminal. The MRBF busbar is rated for 300A total and max 240A per terminal. If, as @dlochner says, the Inverter and battery are on the same terminal the 300A should not affect the bus as it is a direct connection. Any thoughts?

Thanks
Tim

 

[dlochner]

Two thoughts. First the ANL fuses are pretty fragile as such they need to be protected from errant things. The ends of the fuse are 2 thin metal strips that are easily bent and they are exposed, a cover is needed, not sure how you would do that.

Second, it would be better to put the solar cable at the end of the bus bar rather than the middle.

 

[Justin_NSA]

I did something very similar as @dlochner. Lined up some ANL holders and connected them with a copper bar custom drilled.
View attachment 190125

likewise. Mainsail has an article (naturally) on doing this too.

 

[Tim22]

Two thoughts. First the ANL fuses are pretty fragile as such they need to be protected from errant things. The ends of the fuse are 2 thin metal strips that are easily bent and they are exposed, a cover is needed, not sure how you would do that.

Second, it would be better to put the solar cable at the end of the bus bar rather than the middle.

Perhaps the best thing would be to replace the ANL fuse with an MRBF fuse block (see photo) attached to the busbar’s common terminal.
A second idea might be to leave the Inverter unfused at the busbar and rely on the 300A MRBF at the battery terminal.

Also, I agree that the Solar cable should be moved to the end.

Anyone have a link to Maine’s article? I looked for it but couldn’t find it

Thanks

Tim

 

[Ward H]

Here is the link:
Installing a battery charger
Scroll down about 2/3rds. There are some real good photos of the fuse bus bar.
Here is another thread discussing ANL or MRBF fuses on a busbar that might be interesting. ANL VS MRBF

That MRBF Fuse Block you show was advertised but not out yet when I was putting my system together. I could have put MRBF Terminal bars and fuses on a bus bar but that would have cost more than the ANL setup. It would also have moved the cables away from the side of the battery box. Using ANL fuse blocks kept the cables nice and close to the side wall saving some space to allow the room for the two GC-2 6v batteries I installed.

Here's another photo taken as I was putting the system together. I bought the copper bar from McMaster Carr and drilled the holes where they were needed.

 

[Ward H]

"Perhaps the best thing would be to replace the ANL fuse with an MRBF fuse block (see photo) attached to the busbar’s common terminal.
A second idea might be to leave the Inverter unfused at the busbar and rely on the 300A MRBF at the battery terminal."

The MRBF Terminal block is designed to fit on the 3/8" stud of your battery. The studs on the MRBF Fuse Block are 5/16". While you could put a washer under the nut, I'm not sure I would want the looser fit of the terminal block on the smaller stud.

I think your second idea is a good one and meets fusing requirements.

 

[Maine Sail]

1- Inverters should use Class T fuses.

2- MRBF fuse holders and fuses can be direct mounted to a heavy duty busbar. Don't forget to cover the busbar. One reason we don't sell the double MRBF holders and the

 

[DArcy]

I looked at the Blue Sea MRBF fuse block but rejected it as I don’t think it has the capacity. The charger and solar controller are relatively low fuse at 25 & 50 Amps. The 1800w inverter, however, suggests fusing at 300A.

I like the idea of bussing the ANL fuse holders. Is there a formula to calculate the size required? I was looking at the 600A Blue Sea Busbar so it would need to have the same capacity.

Hi Tim, I'm glad to see you're keeping the boat projects going over the winter
You asked is there formula for the size of the busbar and there is... sort of. The concerns are voltage drop and heat. The good news is copper is very conductive so the size limitations tend to be more practical than electrical. Here is an example showing a 1" x 3/8" x 3" long busbar with a 300 A load. I know I'm mixing units in this example but I'm using Mathcad which sorts all that out in the background.

The voltage drop is minimal and the power dissipation is fairly low so won't be a thermal issue since copper is also a very good thermal conductor. Both voltage drop and power are proportional to resistance which is inversely proportional to the cross section area so doubling the thickness will half the power or voltage drop. Conversely, doubling the length will double the voltage drop and power dissipation.
If you are going to drill and tap into the copper, I'd go with at least 3/8" thick to accommodate the screw threads.

 

[Tim22]

1- Inverters should use Class T fuses.

2- MRBF fuse holders and fuses can be direct mounted to a heavy duty busbar. Don't forget to cover the busbar. One reason we don't sell the double MRBF holders and the

Thanks Maine, I will use a class T for the inverter. On your second point just wondering where the “MRBF holders and the” was leading. Is it better to use the heavy duty busbar with single MRBF fuse holders as opposed to the three terminal common MRBF fuse block?

Thanks Tim

 

[Maine Sail]

Thanks Maine, I will use a class T for the inverter. On your second point just wondering where the “MRBF holders and the” was leading. Is it better to use the heavy duty busbar with single MRBF fuse holders as opposed to the three terminal common MRBF fuse block?

Thanks Tim

First wire closest to hull (from battery bank and fused at bank with Class T)
Second wire from bulkhead (to house bank battery switch) protected by fuse at the bank as the wire is the same size
Third wire to inverter ON/OFF switch and also protected by the main banks Class T fuse.
MRBF is for the alternator and is a smaller gauge so needed a lower amperage fuse.
Voltage Sense fuse is above the alternator service disconnect switch