Revised Diagram . . . Cables and Fuses Correct?

[davisr]

Recently I posted a diagram and received many helpful suggestions. This thread mostly centered on the routing of the cables and the placement of various components in the main circuit and grounding system.

http://www.cruisersforum.com/forums/...ork-80685.html

I've now gone back and added cable sizes and fuses. Please disregard the vivid colors. They are only there to make things more clear in the diagram. Most cables will in fact be either red (positive) or yellow (neg).

http://cdn.cruisersforum.com/forums/...attach/jpg.gif

I have several questions, but the most important concerns the fusing. Notice the terminal fuse on the House Bank. The distance between the House Bank and the House Primary Bus Bar is 4.5 feet. I could reduce this to 2.5 feet, but I would prefer not to. As I understand from other postings I've read, I believe this cable run as well as the 1 ft. cable run from the Bus Bar to the Battery Switch are protected by this terminal fuse.

My main concern is with the charging circuit (in blue). The positive cable is 7 ft, the negative 6 ft. There is also an additional foot or two in and around the ACR. I spoke with Iota Engineering. They recommended that I use 4 AWG for a run that is over 10 ft. They also recommended that I place a 50 amp fuse or breaker within 18 inches of the battery. As you see in this diagram, I've placed the 50 amp fuse on the bus bar, but it is 4.5 feet from the battery. Will this be okay, especially since I'm using 4 AWG, which normally would be fused with a 125 or 150 amp fuse (as is the 4 AWG leading to the ACR)?

Thanks for the help,
Roscoe

[Andina Marie]

The two 175 amp fuses in your Reserve Bank will be blown if you try to start the engine on position 2. Your Reserve Bank positive should go direct to 2 on the switch and then a 175 amp fuse to the reserve distribution bus if you need it.

[Jbaffoh]

Originally Posted by Andina

The two 175 amp fuses in your Reserve Bank will be blown if you try to start the engine on position 2. Your Reserve Bank positive should go direct to 2 on the switch and then a 175 amp fuse to the reserve distribution bus if you need it.

I disagree. People debate this, but there's only one safe answer. KEEP THE FUSE!!!

I have a 200 amp fuse on the terminal of my reserve battery. It has blown exactly once, and I'm extremely happy it did!

I was having some trouble rebuilding injectors and the injector pump. Around the 4th time I reinstalled the injectors, I forgot to switch off the batteries. As I tightened the last injector, the wrench found an uninsulated terminal on a relay and spot-welded itself in place before the fuse blew. If that fuse were not in place, I doubt I could have broken the wrench free before the 1/0 cable would have ignited.

Sometimes smart people sometimes do stupid things. That's one reason we use fuses.

[Andina Marie]

Originally Posted by Jbaffoh

I disagree. People debate this, but there's only one safe answer. KEEP THE FUSE!!!

I have a 200 amp fuse on the terminal of my reserve battery. It has blown exactly once, and I'm extremely happy it did!

I was having some trouble rebuilding injectors and the injector pump. Around the 4th time I reinstalled the injectors, I forgot to switch off the batteries. As I tightened the last injector, the wrench found an uninsulated terminal on a relay and spot-welded itself in place before the fuse blew. If that fuse were not in place, I doubt I could have broken the wrench free before the 1/0 cable would have ignited.

Sometimes smart people sometimes do stupid things. That's one reason we use fuses.

HUH? Look at his circuit. Read what I said DUH
You NEVER use fuses in starter motor circuits.
A stater motor on a cold engine can draw FULL CCA rating of the battery. That can be over 1,000 amps on a good battery.
The reason fuses are not used in starter motor circuits is the fuse would have to be rated higher than the CCA of the battery to avoid nuisance blows. If the fuse is rated higher than the battery, it is useless, the battery doesn't have enough capacity to blow the fuse.

If your main battery has failed, your engine needs starting, you are drifting toward the rocks, you switch to battery 2 to save the boat and the engine won't start because someone put 175 amp fuses in the starter motor circuit, don't say I didn't warn you.

[mitiempo]

Andina

I regularly fuse starter circuits on small (under 50 hp or so) diesels using ANL or MRBF fuses and have never had a nuisance blow. Using a good size wire, 1/0 or 2/0, and a fuse for its ampacity there should not be an issue. An ANL fuse will handle about 160% of its rating for 500 seconds and much more for the seconds a start requires.

Now on a powerboat with large engines I wouldn't fuse.

By the way davisr has an outboard.

[Jbaffoh]

Originally Posted by Andina

HUH? Look at his circuit. Read what I said DUH
You NEVER use fuses in starter motor circuits.
A stater motor on a cold engine can draw FULL CCA rating of the battery. That can be over 1,000 amps on a good battery.
The reason fuses are not used in starter motor circuits is the fuse would have to be rated higher than the CCA of the battery to avoid nuisance blows. If the fuse is rated higher than the battery, it is useless, the battery doesn't have enough capacity to blow the fuse.

If your main battery has failed, your engine needs starting, you are drifting toward the rocks, you switch to battery 2 to save the boat and the engine won't start because someone put 175 amp fuses in the starter motor circuit, don't say I didn't warn you.

I looked at his circuit and I read what you said, DUH I also said the topic is heavily debated.

And, I stand behind my comment.

Starting my 30hp Perkins, my inrush never reaches 200 amps. I wanted to use a 250 amp fuse, but could not find one locally, so I tried the 200. It's blown once in two years--out of my own stupidity. I'm so glad it was there!

BTW, I have access to 4/0 cable at good prices, and I'm going to upgrade my old wiring. I'll use heavier duty fuses then.

[Maine Sail]

Originally Posted by Andina

HUH? Look at his circuit. Read what I said DUH
You NEVER use fuses in starter motor circuits.
A stater motor on a cold engine can draw FULL CCA rating of the battery. That can be over 1,000 amps on a good battery.
The reason fuses are not used in starter motor circuits is the fuse would have to be rated higher than the CCA of the battery to avoid nuisance blows. If the fuse is rated higher than the battery, it is useless, the battery doesn't have enough capacity to blow the fuse.

If your main battery has failed, your engine needs starting, you are drifting toward the rocks, you switch to battery 2 to save the boat and the engine won't start because someone put 175 amp fuses in the starter motor circuit, don't say I didn't warn you.

"NEVER"??????? Right........ I have hundreds of fuses in starter circuits on sailboat aux engines. They DO NOT nuisance blow if sized appropriately.. We have started our 44HP 4 cyl Westerbeke thousands of times on a 250A ANL. Our old motor used a 200A ANL and again thousands of starts and never a nuisance blow. I even had the cranking circuit fused on our Downeast boat with a MASSIVE Cummins diesel. This boat was used year round in Maine in some VERY cold temps. Never once tripped the fuse. I also have never had a customer blow a starting fuse as a "nuisance" but I have had them blow due to a dropped wrench......

I have one customer with a Yanmar who accidentally swapped his inverter fuse with engine cranking fuse and never knew it. He went two years on a 130A ANL fuse before I noticed it and swapped it out for the 300A fuse I had in there..

This short blew a fuse and likely saved the boat from becoming an inferno. I am pretty sure my customer was glad he, his wife and three kids under eight were not floating in the water waiting to be plucked out by the USCG when all they had to do was replace the $15.00 fuse, a $12.00 wire and a tie mount that pulled free.. I had left him with a spare fuse, as I always do, so he tapped the wire, secured it away from the engine pulley it had fallen against and was back in service in about ten minutes....


Please look at the trip time delays on these fuses before making absolute statements that don't hold water in the real world. "NEVER" Hmmm I probably have tens of thousands of starts on my own and customers boats that prove you CAN fuse starting circuits...


I quote our good friend Nigel Calder here:

"The net result is that nowadays, electrical shorts are probably the number-one cause of fires on boats."

There is simply no excuse for not protecting all high-current circuits , including the cranking circuit."
Nigel Calder Cruising Handbook



Obviously people can do what they want on their own boats. I will continue to recommend bank fusing to all my customers who have motors & cranking circuits that can safely be fused. For those who can't I will install protective conduit and hope they never have a dead short.....

[Andina Marie]

If fuses in starter motor circuits are so essential why don't we see them in automobiles where cables are in a metal vehicle and not even run in conduit?

[Sailmonkey]

When your car burns you walk away. When your boat burns you float (hopefully) aimlessly hoping for help.

[goboatingnow]

Originally Posted by Andina

If fuses in starter motor circuits are so essential why don't we see them in automobiles where cables are in a metal vehicle and not even run in conduit?

My car has a fully fused battery.

Dave

[davisr]

The Blue Sea Systems Dual Power Post serves as a junction for the 4 AWG Yamaha leads and the 1 AWG starting circuit cable. I chose 1 AWG on account of the length of the circuit. It's difficult to believe, but when you add it all up, it comes to 32 ft. It not like I have the batteries and bus bars in some strange location. They are in the lazarette. The battery switch is on the bulkhead directly above this compartment. Several days ago I based my decision to use 1 AWG on what I could extrapolate from Ed Sherman's brief article "Wire Sizing for Outboard Engines."

Wire Sizing For Outboard Engines

Today I spoke with a customer service representative at Yahama Outboards who confirmed this decision. In fact, he said that if I were at 34 ft instead of 32 he would recommend 1/0 cable. He said I was in the 2 AWG range (according to Yahama), but that 1 AWG, of course, would be better.

Even though this outboard is but a 9.9 horsepower engine, it nevertheless requires a minimum of 245 CCA and 323 MCA. Regardless, I have sized the fuses in the starting circuit in accordance with the rule that fuses are meant to protect the wire not the device. Since I plan to bundle these cables (at least for a short distance) I sized the terminal fuses at 175 amps. I used the Blue Sea Systems Wire/Fuse Chart for this.

Based on what I'm hearing in these postings, I should probably add an ANL fuse in the 10 ft run from the Yahama to the Battery Switch. At present, I believe this is the only run that is not fused. The 4 AWG Yamaha leads are 8 ft. The length of the 1 AWG is only 2 ft.

Does this sound right? Should I add an ANL somewhere in this 10 ft run? If so, where?

Thanks,
Roscoe

[davisr]

After giving it some more thought, I updated the diagram in the OP.

1. I removed the 175 amp Terminal Fuse on the Reserve Bank Bus Bar. It seemed unnecessary since I have one on the Reserve Bank itself.


2. I also changed the bus bars from 250 amp to 150 amp (since I have only a 50 amp max load from the house panels and bilge pumps). In this downsizing I changed the 6 post bus bars to 4 post.


3. I'm still uncertain whether to put an ANL fuse on the initial lead from the motor. Not sure how to deal with two different cable sizes (4 AWG and 1 AWG).


How does all this sound?


I appreciate everyone's help,
Roscoe

[Andina Marie]

Looks fine to me.

[avb3]

Originally Posted by davisr

After giving it some more thought, I updated the diagram in the OP.
.............
Roscoe

Can you advise what program you used to draw the circuit layout?

[davisr]

Sure, no problem. It's a program that a great many of us have already: PowerPoint.

If you click on "Insert" and "Shape" you can selec, lines, arrows, circles, squares, etc. I obviously used the lines more than any other. Once you have them inserted, you can click on them and stretch them all over the place, wherever you need to put them.

I also used "Insert" and "Text Box" quite a bit for all the labels. You can move these text boxes sort of like the lines - click and drag.

It took a little while to get the hang of it, but once I did, I could do it pretty quickly. I've used PowerPoint to make diagrams for the branch circuits too. It's really been a big help in planning this project.

Before posting the diagram I always click on "Save As" and then save it as a JPEG file. Easy to upload to the forum.

Regards,
Roscoe