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Old 20-01-2010, 21:09   #16
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The requirement for an OCPD at the output of the source is a holdover from "back in the day" before modern alternators evolved from the old generators. This wording still resides in the CFR so is retained in ABYC E-11. As Rick pointed out, alternators are self-limiting in their current output and are therefore exempt from the requirement for an OCPD at their output stud.

Hope this helps clarify.
Charlie
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Old 20-01-2010, 21:29   #17
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Charlie, I guess I don't understand how the alternator is self limiting. If the positive cable off the alternator were to short out, it would blow the fuse at the battery, but the rgulator would still be powered off of the alternator. Are we then counting on the surge to blow out the alternator diodes? Obviously, I have just enough knowledge of this stuff to be dangerous.

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Old 20-01-2010, 21:44   #18
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It is self-limiting by the design of the stator and rotor windings. It can only put out the current that it was designed for. If the output conductor was chosen with adequate ampacity to match the alternator output, then when the current is flowing in the correct direction, all is well. The conductor is protected from a fault to ground inside the alternator by the over current protection device required at the battery end of the conductor. If this OCPD is eliminated, the conductor will not have enough ampacity to survive the fault to ground event with the definite possibility of fire as the result.
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Old 20-01-2010, 22:04   #19
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Ah, I see. My focus was on a short circuit somewhere in the line form alternator to the battery. My alternator and cable will survive, but I shudder to think of what might be going on at the location of the short with up to 100 amps going through it.
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Old 06-03-2010, 15:13   #20
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Extended Questions

The long story is that while sailing on the East Coast of the DR we had a catastrophic failure of an external Balmar regulator (ARS5) on a Balmar series 6 alternator. We were able to get to a marina in Punta Cana and tried to troubleshoot there. Contrary to some folks experiences, Balmar was very helpful but the regulator was way out of warranty. They informed me that the installation was questionable. We then wired up the internal regulator on the alternator and made it to my home marina. Then, I decided that I'd better double check and do things right. I had assumed that the charging system was installed correctly because the PO had "professionals" working on the boat. Well, I'm finding a lot of problems, especially with poor fusing.

I've been reading through this thread, the one that CharlieJ referred to, and a couple of others. And I'm still confused. Unfortunately the system is pretty complex so I'll start with the simplest comments and questions and perhaps move on from there.

I have three solar panels in series, a Xantrex Freedom 30 charger/inverter with a Link 2000, a Balmar alternator, three batteries in the house bank and a single starting battery (all are Optima D34M's). There are actually 3 breaker panels (for power distribution) because there have been several electrical upgrades and it seems that each time they added another panel. And a Blue Sea 1-2-both-off switch to go from one battery bank to the other.

I think that the first thing is to double check the cables and make sure that they are in good shape and large enough (ampacity) for the respective loads.

I'd like to install a bunch of fuses because the only one that I can find is between the Freedom 30 and the battery battery switch. I saw James S and CharlieJ 's installation and that looks pretty nice but I'm not sure that I can find room for anything like that. However, space won't undercut safety (at this point I'll probably overdesign). I think that I can install several of the MRBF fuses without space problems. Reading through the threads here I don't really understand what the objections are to these, versus the class T fuses. With space considerations and strain relief, the class T fuses are going to be a lot harder to install close to the power sources. An aside: CharlieJ refers to B+ cables. I can usually tell from context what he means but exactly what is B+??

I'm seriously thinking of using a Digital Duo Charge for charging the starting battery and setting up the 1-2-both-off battery switch for emergency switching. I'd appreciate any comments about that design.

I'd also prefer not to put a fuse between the starting battery and starter solenoid so I'm thinking of enclosing that cable in a "conduit" to prevent shorting due to possible chafe or other gremlins attacking it. But, I'd put a fuse in that cable too, if someone could convince me that there is a big enough one and there is a good safety reason.

I'm still debating the need for two fuses (one at each end) of the battery-alternator cable. Maybe just one at the battery end and enclosing the cable in a conduit. I don't mind the $35-40 for an MTBF at each end it's just that it seems better to keep things simple with fewer connections.

Well, any comments and suggestions will be greatly appreciated. I've got to start ordering the parts and pieces 'cause I'd like to get this all straight before doing any more serious sailing.

Thanks!!!
Bill
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Old 07-03-2010, 09:19   #21
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Bill-
Sorry to hear about your problems.

Quote:
We then wired up the internal regulator on the alternator and made it to my home marina.
I guess it is a good news/bad news issue. Good news that the PO chose the versatile 6 Series Balmar with the internal "get home" regulator. Bad news that he didn't have the optional SPDT switch wired in so that when you had your alternator failure, you could simply switch from external regulation to internal regulation.

Quote:
I think that the first thing is to double check the cables and make sure that they are in good shape and large enough (ampacity) for the respective loads.
Excellent place to start. While you are at it, identify each conductor with a number, the conductor's size, color, source and load on a simple, 5 column sheet. Typically conductors have adequate ampacity unless they were installed by absolute morons. Voltage drop is another matter altogether. I find the Blue Sea Systems' foot-amps method to be very quick and easy to use, even in the field, to verify ampacity (inside and outside of machinery spaces) and voltage drop. Voltage Drop in Conductor - Wire Sizing Chart - Resources - Blue Sea Systems

Quote:
I think that I can install several of the MRBF fuses without space problems. Reading through the threads here I don't really understand what the objections are to these, versus the class T fuses.
I don't understand either. The MRBF are small, have a 10,000 amp AIC, and are not terribly expensive. The only requirement that I have seen for the larger, more expensive, fast acting Class T fuse is in the B+ to an inverter or inverter/charger.

[QUOTE][ An aside: CharlieJ refers to B+ cables. I can usually tell from context what he means but exactly what is B+??/QUOTE]

Sorry...Most "normal" people would say "positive" or "hot". I use the B+ to differentiate it from the B- return to the Vessel Ground. Most "normal" people would use "negative" or "ground" to describe this conductor. Besides, it takes fewer keystrokes!

Quote:
I'm seriously thinking of using a Digital Duo Charge for charging the starting battery and setting up the 1-2-both-off battery switch for emergency switching. I'd appreciate any comments about that design.
That will work and allows you to mix battery chemistries between the house and starting bank. The caveat would be if you use your starting battery for additional service such as an anchor windlass or bow thruster. In this case, you could deplete your starting battery faster than you can charge it through the 30 amp DuoCharge.

If you don't have mixed chemistries, consider an auto charge relay. I am partial to the relatively new magnetic latching units from Blue Sea with a manual over ride capability. ML-Series Heavy Duty Automatic Charging Relay - PN 7622 - Blue Sea Systems Install this and eliminate the 1-2-Both-Off switch. It is rated at 500 amp continuous so it can drive a thruster or windlass.

Quote:
I'd also prefer not to put a fuse between the starting battery and starter solenoid so I'm thinking of enclosing that cable in a "conduit" to prevent shorting due to possible chafe or other gremlins attacking it. But, I'd put a fuse in that cable too, if someone could convince me that there is a big enough one and there is a good safety reason.
No reason and no Standard requirement to put an OCPD in the starter's B+. Chafe protection is an EXCELLENT idea. Ensure that the conductor is well supported at a minimum of every 18 inches and that there is an insulating boot on the conductor/starting solenoid stud . Install an On-Off switch in the B+ between the battery and the starter. Do all of this, and you will be in compliance and smart.

Quote:
I'm still debating the need for two fuses (one at each end) of the battery-alternator cable. Maybe just one at the battery end and enclosing the cable in a conduit. I don't mind the $35-40 for an MTBF at each end it's just that it seems better to keep things simple with fewer connections.
Not necessary for an OCPD at both ends. See my Post #16 in this thread. The OCPD is required where it attaches to the B+, be that at a bus bar, the battery terminal, a switch, etc.

Hope this helps.
Charlie
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Old 09-03-2010, 15:34   #22
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Actually, when all was said and done, the voltage regulator meltdown might well have been a blessing. It forced me to look through the circuitry and I'm sure that I'll feel a lot better when I've completed the improvements.

Thanks a lot for the advice and comments. They really help.

What about ANL fuses? They look to be somewhat smaller than the class T fuses and blocks. But I think that I'll go for the MTBFs they look so much simpler to install and keep up.

I haven't laid out the upgrade circuits but I'm sure that I'll have to replace some of the main battery cables. I suppose that the most economical and simplest thing is to measure the cable lengths needed and get someone to crimp on connectors since I don't think that I really want to buy a crimper for cables of that size. What are the cable specifications that are compliant with ABYC and are good for marine environments?

And...are there any comments or experience with the Balmar digital duo charger?

Thanks again!!
Bill
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