"Standard" Rewire but with sizing questions

[itsjustgher]

Hello, and let me start by saying what a wonderful and amazing forum this is and the wealth of knowledge that I have gained from not only Mainesail, but all the other contributors!

Taking what I have learned I came up with the attached diagram for my rewire. I'm going with the battery "use" switch method which is popular around these parts, so this may look familiar.

I feel like I have a solid plan, but definitely need an idiot check to make sure there aren't any bonehead mistakes. I'm curious to know if I got the wire sizing and circuit protection levels correct. Once this passes muster, its off to the races to buy just about every termination tool suggested by Maine.

Thanks in advance!!!

 

[FastOlson]

I sometimes find that a proper diagram is easier to understand if it can also be re-rendered with the wiring and devices oriented like the layout in the actual boat.
When I have done a similar one for our boat it was much more understandable to me when reviewed later.

Having said that, it's probably just me! My late father was an electrical engineer and licenced electrician and was always comfortable with a true diagram like yours.

One interesting point about sizing, the OEM sizing was always a compromise between more wire expense and the minimum acceptable line loss. When re-wiring most circuits it's good to revisit the potential loss with each size of contemplated wire (and amp load) and err towards to larger dia.

Best,
Loren

 

[itsjustgher]

Trust me when I say that its not just you! This is one of many diagrams I've made in the process. The hard part for me is that as a merchant mariner, I dont get to be home to measure anything for another three weeks.

Pictures and diagrams can only do so much when trying to understand placement and distances.

 

[JK_Boston_Catalina310]

I made some comments on the attached PDF.

Here are a couple of additional comments to those. Is "LPG" for a propane leak detector? If so, I have no problem with that set up except you should add fuse sizes for Radio, LPG and Bilge. Oh, I assume the bilge wires will go through an on/off/auto switch on the panel.
What about placement on the boat? When I did my wiring project I put the positive and negative hubs (equivalent of your SafetyHub) in the battery area mounted on a piece of starboard.

If you plan to mount the EcoCharger near the battery selector switch, the setup you have could work. But your wire size would be too small there. You would have to size it based on the full length to the 1 or 2 post and then from the 1 or 2 post to the battery. It may be easier to mount it in the battery area and have it go directly from the house bank to the aux bank.

I did a similar remodel this winter. I am very happy I did and love the battery monitor.

Good luck and fair winds,

Jesse

 

[Stu Jackson]

Here are some comments on connecting the EC to the switch:

http://c34.org/bbs/index.php/topic,6225.0.html

If you click on the links to the wiki, it'll explain why. Also includes a link to some good EC information from Maine Sail.

 

[Maine Sail]

It looks good. I will say that a 35A alt is going to be quite undersized for a 450Ah house bank. I am going to guess a Hitachi/Yanmar? They offered a 35A as standard equipment....

 

[itsjustgher]

Is "LPG" for a propane leak detector?

Roger, for the leak detector.

What about placement on the boat? When I did my wiring project I put the positive and negative hubs (equivalent of your SafetyHub) in the battery area mounted on a piece of starboard.

This is what really got me thinking. I have decided that instead of run the wires (for the echo charger, starter, etc) all the way up to the battery switch, bring the battery switch down to it. This will create straighter, shorter shots of wire to the hub. It will also work out logically for running the negative bus to the safety hub. As for the negative bus, I was thinking that I would be working with such large wire that it would be hard to attach them all to the screw terminals, and I did not want to over stack the post terminals. But with some relocating and shortening of runs I can use smaller gauge wire. That and I stopped way over compensating for additional solar, larger alternator, etc.

If you plan to mount the EcoCharger near the battery selector switch, the setup you have could work. But your wire size would be too small there. You would have to size it based on the full length to the 1 or 2 post and then from the 1 or 2 post to the battery. It may be easier to mount it in the battery area and have it go directly from the house bank to the aux bank.

By bringing the battery switch to the engine compartment the distance to run is greatly reduced. Is it difficult to increase the wire gauge on the Xantrex? I'm of the opinion that just splicing bigger wire to the stock pigtails is a no no.

As for the questions on the PDF.

You have 4 AMI spots on the SafetyHub, why not wire this (alternator output) there instead? Share the stud/fuse with the "solar"

In my new design I have moved the alternator to a 100A AMI fuse on the SafetyHub. The solar is going to a 30A ATC fuse spot. Even though I am using #6 wire for voltage drop, the 30A fuse should be adequate, correct? I was trying to size the fuses for the wire, but going smaller should not hurt?

Why are you running this (ground wire from starter) to the Neg. Bus? It's already grounded through the motor. If you want to add a ground, why not direct to the ground stud on the motor?

Good question. I had read somewhere that it can be unwise to ground the alternator and starter through the motor as there can be a lot of resistance, paint, bad connections, etc. in the path. While I dont think my motor is that bad off, I was thinking about playing it safe. Is it feasible to take the negative from the alternator to the starter to a common ground as I have seen elsewhere?

2/0 (from battery switch common to starter) could be overkill. What motor and how long is the run?

Originally the total run was about 30ft round trip. Take in mind that my distances are approximate as I am in S. Chicago and the boat is in Key West. I'm basically taking my best guestimate on distance as the wire would have to be run. With that said, in my new design the distance is going to be tops 10ft round trip. The motor is a Yanmar 3HM, and to be honest, the whole how a starter works and how much it draws is pretty confusing for me. I was going to go big and hope for the best. This may be incorrect, but I planned on the 300A MRBF on the batteries to protect the 2/0 wire to the starter, not concerned about inrush as the MRBF is a slow burn fuse. But if I can go smaller with that wire in my new setup, that would be awesome as 2/0 is expensive!

Thank you for the great input so far, these changes should give me a simpler wire job and save me a boat load of money!

 

[itsjustgher]

It looks good. I will say that a 35A alt is going to be quite undersized for a 450Ah house bank. I am going to guess a Hitachi/Yanmar? They offered a 35A as standard equipment....

You got it, 35A Hitachi on a Yanmar 3HM. JK's post and the catalina rewire wiki got me thinking about this. Changing the alternator would be nice, if it is just a bolt on process. The downfall is that I will then have two 35A spares :neutral:

Ideally I would upgrade the solar to help with the bulk of my charging but the cost in that is most likely exponentially larger than just a new alternator. I have gotten most of my solar info from http://handybobsolar.wordpress.com/ and would love to have to not run my main to charge. But I also understand that my consumption is the key to that goal.

 

[JK_Boston_Catalina310]

This is what really got me thinking. I have decided that instead of run the wires (for the echo charger, starter, etc) all the way up to the battery switch, bring the battery switch down to it. This will create straighter, shorter shots of wire to the hub. It will also work out logically for running the negative bus to the safety hub. As for the negative bus, I was thinking that I would be working with such large wire that it would be hard to attach them all to the screw terminals, and I did not want to over stack the post terminals. But with some relocating and shortening of runs I can use smaller gauge wire. That and I stopped way over compensating for additional solar, larger alternator, etc.

...

By bringing the battery switch to the engine compartment the distance to run is greatly reduced. Is it difficult to increase the wire gauge on the Xantrex? I'm of the opinion that just splicing bigger wire to the stock pigtails is a no no.

It sounds like you need to visit the boat and estimate the lengths before you can finalize wire and fuse sizing. Blues sea systems has a great chart for that: http://assets.bluesea.com/files/resources/reference/20010.pdf

As to the Xantrex Echo-charger, I really can't comment. I didn't know the leads were already attached. I used the Blue Sea ACR. (http://svsmitty.wordpress.com/2013/03/04/electrical-charging-system-upgrade-mostly-complete/) I guess I would suggest some more research on the Echo-Charger. For one thing, it appears to be limited to 15A. So your alternator will be limited. If you go bigger with any of your other charging sources the would be as well. Might not be a big issue since it's going to an aux. battery. I just don't know enough about it.

In my new design I have moved the alternator to a 100A AMI fuse on the SafetyHub. The solar is going to a 30A ATC fuse spot. Even though I am using #6 wire for voltage drop, the 30A fuse should be adequate, correct? I was trying to size the fuses for the wire, but going smaller should not hurt?

You could have a problem here. I suggest you read MaineSail's article on Fusing Voltage Drop (http://www.pbase.com/mainecruising/fuse_voltage_drop)

Good question. I had read somewhere that it can be unwise to ground the alternator and starter through the motor as there can be a lot of resistance, paint, bad connections, etc. in the path. While I dont think my motor is that bad off, I was thinking about playing it safe. Is it feasible to take the negative from the alternator to the starter to a common ground as I have seen elsewhere?

I commented a little to quick on this one. What I did, basically just copying MaineSail, is put a second negative bus bar at the engine. I then took off the starter, cleaned off the paint and rust from one of the bolt locations and put a 1/0 gauge wire from there to the engine negative bus bar. The negative for the alternator was also connected to this bus bar. I put a 1/0 gauge wire from ground stud on the engine to the bus bar. Finally, I connected the 1/0 gauge wire that went to the engine ground stud from the battery post (reconnected to the battery negative bus bar as part of the project) and the 1/0 gauge wire that went from the engine ground stud to the negative bus behind the electic panel to the engine negative bus. Boy, that sounds confusing. Here is how MaineSail explained it better than I just did. http://forums.sbo.sailboatowners.com/showthread.php?p=999189&highlight=negative bus bar

Originally the total run was about 30ft round trip. Take in mind that my distances are approximate as I am in S. Chicago and the boat is in Key West. I'm basically taking my best guestimate on distance as the wire would have to be run. With that said, in my new design the distance is going to be tops 10ft round trip. The motor is a Yanmar 3HM, and to be honest, the whole how a starter works and how much it draws is pretty confusing for me. I was going to go big and hope for the best. This may be incorrect, but I planned on the 300A MRBF on the batteries to protect the 2/0 wire to the starter, not concerned about inrush as the MRBF is a slow burn fuse. But if I can go smaller with that wire in my new setup, that would be awesome as 2/0 is expensive!

You need to do some research on what your engine draws but based on a typical 150A with higher inrush, you might be able to reduce the size on the starter wiring.

Good luck