Another wiring diagram for review

[marchem]

1982 Catalina27, Universal 5411. Mostly original wiring (I think). Battery wires currently #6.

After reading as much as I could here and asking some questions I'd like to get comments on my proposed wiring diagram. I'm increasing wire size to #4, running the alternator straight to battery #1, adding an ACR, ground busbar, and fusing, connecting alternator and starter ground together.

Questions I still have:
-is #4 wire size ok? The alternator is only 55A and I don't envision going larger or adding more battery capacity, just weekend cruising with minimal DC requirements.
-is stacking 2 or 3 lugs on the MRBF ok?
-are my fuse sizes appropriate?
-would the new BlueSeas mini-ACR (65A) be ok to use, instead of the SI-ACR? Smaller and less expensive.

I'm also going to eliminate the trailer plugs, and remove the ammeter from the engine panel, but those are simpler jobs.

Thanks in advance for any thoughts and advice. There's a wealth of knowledge here and a bunch of great folks.

 

[mmedley2]

The suitibilty of the #4 wire is dependent on the length as well as the max current and voltage. The result of insufficiant area (gauge) is voltage drop (VD). Here is a free link that calculates VD http://www.powerstream.com/Wire_Size.htm

 

[JK_Boston_Catalina310]

By no means am I an expert, so take what I say with a grain of salt. But based on advice I have gotten from Mainesail, I did notice a couple of things.

1) Why is the alternator connected to the starter if the alternator is wired direct to the battery bank #1?

2) The #4 wire for the starter and the batteries seems too small. Universal recommends a minimum of 2 gauge for an 8 foot run. Longer than 8 feet you start going up in size.

3) The #10 wire for the ac charger also seems small but I guess that would really depend on the charger.

4) The 100 amp fuse is probably too small for starting. I had 150 amp and Mainesail recommended I increase that or else I may have a lot of nuisance blows that I will have to constantly be replacing.

Hope this helped.

Jesse

 

[Maine Sail]

By no means am I an expert, so take what I say with a grain of salt. But based on advice I have gotten from Mainesail, I did notice a couple of things.

1) Why is the alternator connected to the starter if the alternator is wired direct to the battery bank #1?

2) The #4 wire for the starter and the batteries seems too small. Universal recommends a minimum of 2 gauge for an 8 foot run. Longer than 8 feet you start going up in size.

3) The #10 wire for the ac charger also seems small but I guess that would really depend on the charger.

4) The 100 amp fuse is probably too small for starting. I had 150 amp and Mainesail recommended I increase that or else I may have a lot of nuisance blows that I will have to constantly be replacing.

Hope this helped.

Jesse

You learn well! Spot on....

 

[marchem]

By no means am I an expert, so take what I say with a grain of salt. But based on advice I have gotten from Mainesail, I did notice a couple of things.

1) Why is the alternator connected to the starter if the alternator is wired direct to the battery bank #1?

Jesse, thanks for the comments. That's a ground wire connecting them directly to eliminate the case ground, per MS's comments. There's also a ground wire running from the starter to the ground busbar at the batteries.

2) The #4 wire for the starter and the batteries seems too small. Universal recommends a minimum of 2 gauge for an 8 foot run. Longer than 8 feet you start going up in size.

I saw that table. The engine is only a 2 cylinder, so the starting current might be less than what the table is based on, but going to #2 wire for the starter and batteries seems like a good idea. It seems like I could leave the alternator and ACR wires at #4, since there is max 55A there, although that would make the fusing more complex (see below).

3) The #10 wire for the ac charger also seems small but I guess that would really depend on the charger.

It's a Statpower/Xantrex Truecharge 10TB 10A charger. With only 2' #10 has <0.5% drop @ 10 A, so I feel ok about that (Xantrex says #14 is ok, but that really seems too small).

4) The 100 amp fuse is probably too small for starting. I had 150 amp and Mainesail recommended I increase that or else I may have a lot of nuisance blows that I will have to constantly be replacing.

175A looks like the right value for the #2 wire, but then I need to use #2 instead of #4 everywhere, or add a new 100-125A fuse for the #4 wires-which probably means a busbar.

 

[marchem]

You learn well! Spot on....

What are your (and other's) thoughts about stacking lugs on the MRBF? With 5 wires and a dual MRBF I've got to stack at least 3 and possibly 4 wires. It might be easier to just install a positive bus, and put additional MRBFs on it, but that raises the cost significantly.

Maybe I'm over analyzing this....

 

[Maine Sail]

What are your (and other's) thoughts about stacking lugs on the MRBF? With 5 wires and a dual MRBF I've got to stack at least 3 and possibly 4 wires. It might be easier to just install a positive bus, and put additional MRBFs on it, but that raises the cost significantly.

Maybe I'm over analyzing this....

One large wire plus one small wire if needed but the smaller wire can go direct to the battery post because it too should be fused. These "cubes" are not really meant for stacking wires onto. The MRBF is only sized to protect the largest wire.

What are all the lugs you are trying to stack? With a dual MRBF I do alt and battery main conductor..

Also #10 is awfully small for a DC panel. I'd much rather see #6 or so. That way we can assure yiu are hitting the max 3% voltage drop for critical circuits.

If your ACR can be mounted close to the battery switch then simply connect to the #1 & #2 posts as it keeps the battery posts a little cleaner.

 

[marchem]

One large wire plus one small wire if needed but the smaller wire can go direct to the battery post because it too should be fused. These "cubes" are not really meant for stacking wires onto. The MRBF is only sized to protect the largest wire.

What are all the lugs you are trying to stack? With a dual MRBF I do alt and battery main conductor..

That makes sense to do the alt and battery main, but I've still got the ACR, AC charger, and solar charger to attach. I think the ACR should be fused and have the same wire size as the alternator, so stacking those two, if possible, seems to make sense. Since the AC and solar are low current I could fuse them directly to the battery post.

 

[Maine Sail]

That makes sense to do the alt and battery main, but I've still got the ACR, AC charger, and solar charger to attach. I think the ACR should be fused and have the same wire size as the alternator, so stacking those two, if possible, seems to make sense. Since the AC and solar are low current I could fuse them directly to the battery post.

If you wire the ACR with the same size wire as the battery, the battery fuses cover the ACR.. You can then simply wire the ACR behind the 1/2/B switch and connect it to #1 & #2. Short little pigtails from the ACR to the battery switch an the MRBF's protect you......

 

[marchem]

If you wire the ACR with the same size wire as the battery, the battery fuses cover the ACR.. You can then simply wire the ACR behind the 1/2/B switch and connect it to #1 & #2. Short little pigtails from the ACR to the battery switch an the MRBF's protect you......

Of course! That's brilliant. I was thinking that the ACR needed to be close to the battery, but that's not true. I'll rework the diagram and repost. Thanks so much for all the help you've provided. Your willingness to patiently explain these issues is invaluable to the rest of us.

 

[SailingHarry]

You've had a lot of good responses, but I'll add a few.

* The #4 wire to the starter. It's rated for 136A in the engine room, so you could up the fuse size to a bit higher if you wanted.
* Again on that #4, it is small, but then again, so is your engine (11hp). It's a #6 now, so #4 is an upgrade (I assume it works OK right now, probably factory original, right?)?
* My 27 hp Volvo 2 cylinder has a 1.2KW starter on it. That's 100A, and I've measured about that same current. But a 100A fuse is good for a lot more than 100A for very short durations (like inrush, and even cranking).
* Bottom line on the #4, especially if you up the fuse to 125A or so, is you should never see it blow.
* CAUTION: That switch on the output of the alternator is an invitation to blown diodes! What is it for? I don't see it serving any purpose.
* The #10 to the DC panel is probably too small. Add up all the loads on the DC panel, and then look at the drop on those lines. You probably will have a larger drop at the panel than allowed, and that is BEFORE you run to the loads. On my boat, I took it to a #4 - probably overkill. But a #6 or #8 would be a good upgrade. My Sabre 34 came factory with a #8.
* The 30A fuse to the DC Panel is probably too small. Once you up the line to the panel, you probably can up the fuse (and even at a #10, you could make it a 60A). That fuse should be a "disaster fuse" and really should be set to blow only if you have a serious short in the panel feed -- so use the largest fuse the wire can handle. The panel is where all the real control and protection should be happening.
* This next point is a strong issue for me. I almost sank my boat on my delivery trip because of too many wires on the battery (and a bunch other problems too) that led to confusion. I like a bare minimum of wires on the battery. EVERY vendor wants his wire to go "direct to the battery." It loads up the battery lugs (mechanical loads), it makes it confusion to wire, it increases risk of shorting when using tools near the battery, it makes it hard to put the wires on the battery, etc. I hate it. Me, I would take every thing except the 100A fuse off each battery, and move them to the A/B switch. A bus, a distribution panel, etc, would even better, but moving it all up to the A/B switch gets it off the battery. One fuse, one wire to the switch. Clean, neat, safe. Some folks would argue with me on some items (battery monitor, etc) and they have a good argument -- I just disagree.
* Seriously consider a small distribution panel on the house battery (fuse or breakers). It's already complicated in your drawing, and you haven't shown the battery monitor system, the remote sense for the regulator, the constant power to the stereo, the constant power to the fridge, the constant power to the bilge pump, etc. -- and those won't work on the #10 concept so you'll need more fuses.
* Your boat is 27', it's just a day/weekend-cruiser, and it's old (not a dig -- mine's a '79). It's never going to sail around the world, and it's never going to sell for a billion dollars. Resist the urge to make it as well equipped as the Go-Fast-44 in the next slip. You are making decent improvements, and you are making is safer. Keep a minimum level of safety and properness in mind, but don't go overboard.
* I *love* the House/Spare concept. It's what I use. If you ever replace the batteries, I'd be tempted to try and shift the sizes a bit. Get a little bigger House, and if needed to make it fit a little smaller Spare. I have started my 27HP Volvo on the itty bitty battery out of my Honda Civic with no problems.

OK, I said a lot more than "a few." Hope it helps.

Harry
Analysis
'79 Sabre 34
Mill Creek, Annapolis

 

[Stu Jackson]

* CAUTION: That switch on the output of the alternator is an invitation to blown diodes! What is it for? I don't see it serving any purpose.

It's normally ON all the time. It only gets opened when working on the alternator, since that line is always HOT. Some of us simply remove the fuse when working on the engine. It's a very good idea.

 

[SailingHarry]

* CAUTION: That switch on the output of the alternator is an invitation to blown diodes! What is it for? I don't see it serving any purpose.

It's normally ON all the time. It only gets opened when working on the alternator, since that line is always HOT. Some of us simply remove the fuse when working on the engine. It's a very good idea.

Adds a small bit of complexity (especially on a 27' boat), but does indeed seem like a neat idea. I've taken my alt. out a couple of times, and always opted for the "try not to short it" rather than the better (but more complex) option of "undo the fuse." It could probably be one of those automotive style disconnects with the removable key.

Something like this?
http://www.batterymart.com/p-battery-cut-off-switch.html#pr-header-ACC__41860

Harry

 

[Maine Sail]

You've had a lot of good responses, but I'll add a few.

* The #4 wire to the starter. It's rated for 136A in the engine room, so you could up the fuse size to a bit higher if you wanted.

Amen. Min size I like to see for any fuse called upon for starting duty is 200A.

* My 27 hp Volvo 2 cylinder has a 1.2KW starter on it. That's 100A, and I've measured about that same current. But a 100A fuse is good for a lot more than 100A for very short durations (like inrush, and even cranking).

This is a 1.2kW starter:

The "amps" is the average amperage during the duration of starting:

* Bottom line on the #4, especially if you up the fuse to 125A or so, is you should never see it blow.

Any fuse below 200A, used regularly for starting small sailboat AUX engines, runs a risk of a nuisance trip. ABYC allows for going to 150% of max ampacity. With undersized cables this can be necessaryif you want over current protection on the battery wires..

* CAUTION: That switch on the output of the alternator is an invitation to blown diodes! What is it for? I don't see it serving any purpose.

It is called a "service disconnect" and allows isolation of 12V from the engine/alternator so you don't short something while working on it. Ideally it should be located in the engine bay visible to a mechanic and not crew.

* The #10 to the DC panel is probably too small. Add up all the loads on the DC panel, and then look at the drop on those lines. You probably will have a larger drop at the panel than allowed, and that is BEFORE you run to the loads. On my boat, I took it to a #4 - probably overkill. But a #6 or #8 would be a good upgrade. My Sabre 34 came factory with a #8.

Larger wire in the marine environment is never a bad thing. Catalina was one of the most "lax" when it came to "best pracitices" as related to wiring... Critical circuits such as nav lights require a max of 3% voltage drop.. Pretty hard to do with a 10Ga wire feeding the whole panel. Any wire feeding a DC panel should be sized for the worst case of all logical loads...

* The 30A fuse to the DC Panel is probably too small. Once you up the line to the panel, you probably can up the fuse (and even at a #10, you could make it a 60A).

Yep!

That fuse should be a "disaster fuse" and really should be set to blow only if you have a serious short in the panel feed -- so use the largest fuse the wire can handle. The panel is where all the real control and protection should be happening.

This applies to ALL wire protecting fuses especially those with large in-rush loads like engine starting.

* This next point is a strong issue for me. I almost sank my boat on my delivery trip because of too many wires on the battery (and a bunch other problems too) that led to confusion. I like a bare minimum of wires on the battery. EVERY vendor wants his wire to go "direct to the battery." It loads up the battery lugs (mechanical loads), it makes it confusion to wire, it increases risk of shorting when using tools near the battery, it makes it hard to put the wires on the battery, etc. I hate it.

Me too! The operative word here is BUS BARS..

Me, I would take every thing except the 100A fuse off each battery, and move them to the A/B switch.

Even worse for me is cluttering up a battery switch. These posts are shorter, more cramped and a far worse situation than loading up a battery post. Mocing it to the cramped space of a battery switch is not one I recommend.

A bus, a distribution panel, etc, would even better, but moving it all up to the A/B switch gets it off the battery. One fuse, one wire to the switch. Clean, neat, safe. Some folks would argue with me on some items (battery monitor, etc) and they have a good argument -- I just disagree.

I have seen more issues with heavily loaded "C" posts on battery switches than heavily loaded battery posts. Better to go from the "C" post to a + dist bus bar or sub fuse panel.

* Seriously consider a small distribution panel on the house battery (fuse or breakers). It's already complicated in your drawing, and you haven't shown the battery monitor system, the remote sense for the regulator, the constant power to the stereo, the constant power to the fridge, the constant power to the bilge pump, etc. -- and those won't work on the #10 concept so you'll need more fuses.

There are only a few items that need to go direct to the battery and those are pretty much voltage sensing items. Battery monitor or regulator are but two but a dedicated volt sense bus can also be created to minimize battery post wires.. The bilge pump can go direct to the #1 or #2 post (which ever is house) on the battery switch if you lack space.. In a PROPERLY wired system nothing else needs to go direct to the battery post.. Everything else can be on a separate bus.

 

[Bill Roosa]

I have to say I've never seen so many ways to wire two batteries and a charging system together than on a boat. this is one of the less complicated ones i've seen BTW.

How far are the battery terminals from the engine?

 

[Bill Roosa]

also where is the alternator regulator and regulator battery voltage sensing wire?

 

[Maine Sail]

also where is the alternator regulator and regulator battery voltage sensing wire?

Probably a stock alt & regulator that senses its own B+...

 

[marchem]

You've had a lot of good responses, but I'll add a few.

* The #4 wire to the starter. It's rated for 136A in the engine room, so you could up the fuse size to a bit higher if you wanted.
* Again on that #4, it is small, but then again, so is your engine (11hp). It's a #6 now, so #4 is an upgrade (I assume it works OK right now, probably factory original, right?)?
* My 27 hp Volvo 2 cylinder has a 1.2KW starter on it. That's 100A, and I've measured about that same current. But a 100A fuse is good for a lot more than 100A for very short durations (like inrush, and even cranking).
* Bottom line on the #4, especially if you up the fuse to 125A or so, is you should never see it blow.

I'm pretty sure it's mostly original wiring. My latest plan uses a 175A fuse with #2 wire for the starter. I do stick with #4 and 125A for the alternator.

* The #10 to the DC panel is probably too small. Add up all the loads on the DC panel, and then look at the drop on those lines. You probably will have a larger drop at the panel than allowed, and that is BEFORE you run to the loads. On my boat, I took it to a #4 - probably overkill. But a #6 or #8 would be a good upgrade. My Sabre 34 came factory with a #8.
* The 30A fuse to the DC Panel is probably too small. Once you up the line to the panel, you probably can up the fuse (and even at a #10, you could make it a 60A). That fuse should be a "disaster fuse" and really should be set to blow only if you have a serious short in the panel feed -- so use the largest fuse the wire can handle. The panel is where all the real control and protection should be happening.

I agree. I think I'll use #6 and a 60 or 100A Blue Sea AMI fuse, depending on which DC panel I go with.

* This next point is a strong issue for me. I almost sank my boat on my delivery trip because of too many wires on the battery (and a bunch other problems too) that led to confusion. I like a bare minimum of wires on the battery. EVERY vendor wants his wire to go "direct to the battery." It loads up the battery lugs (mechanical loads), it makes it confusion to wire, it increases risk of shorting when using tools near the battery, it makes it hard to put the wires on the battery, etc. I hate it. Me, I would take every thing except the 100A fuse off each battery, and move them to the A/B switch. A bus, a distribution panel, etc, would even better, but moving it all up to the A/B switch gets it off the battery. One fuse, one wire to the switch. Clean, neat, safe. Some folks would argue with me on some items (battery monitor, etc) and they have a good argument -- I just disagree.
* Seriously consider a small distribution panel on the house battery (fuse or breakers). It's already complicated in your drawing, and you haven't shown the battery monitor system, the remote sense for the regulator, the constant power to the stereo, the constant power to the fridge, the constant power to the bilge pump, etc. -- and those won't work on the #10 concept so you'll need more fuses.

Thanks to Maine Sail's suggestions I think I've got that worked out better. I still have 4 wires going to the House battery post, but I think it will work fine.

* Your boat is 27', it's just a day/weekend-cruiser, and it's old (not a dig -- mine's a '79). It's never going to sail around the world, and it's never going to sell for a billion dollars. Resist the urge to make it as well equipped as the Go-Fast-44 in the next slip. You are making decent improvements, and you are making is safer. Keep a minimum level of safety and properness in mind, but don't go overboard.
* I *love* the House/Spare concept. It's what I use. If you ever replace the batteries, I'd be tempted to try and shift the sizes a bit. Get a little bigger House, and if needed to make it fit a little smaller Spare. I have started my 27HP Volvo on the itty bitty battery out of my Honda Civic with no problems.

OK, I said a lot more than "a few." Hope it helps.

It helps a lot. I really appreciate the time and thought you put into this. I'll attach my latest wiring plan. I think it's getting close. The good news is I got to go sailing all three days last weekend, which helps balance out all this thinking and planning.

 

[marchem]

Probably a stock alt & regulator that senses its own B+...

Correct.

 

[marchem]

I have to say I've never seen so many ways to wire two batteries and a charging system together than on a boat. this is one of the less complicated ones i've seen BTW.

I think I'll take that as a compliment.

How far are the battery terminals from the engine?

2-3 feet. 5-6 feet to the 1/2 switch.