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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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  #1  
Old 08-04-2011
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Solving Difficult Electrical Problems

We recently had a difficult problem that involved a gradual decline in the output of our DC charging system (coupled with some apparently anomalous tachometer readings). The details are not relevant to the purpose of this post, but I will email a precis to anyone who requests it via PM.

I am a pretty qualified electrical guy, but the problem stumped me. I then retained a well-known local marine systems organization, and after two days they were stumped. Feeling just a tad desperate by this point, I telephoned Mr. Hamilton Ferris (Hamilton Ferris Power Systems Co., 3 Angelo Drive, Bourne, MA 02532 508-743-9901). Mr. Ferris spent a couple of hours on the telephone with me and solved the problem. The solution was arcane, and I doubt I would ever have figured it out myself.

So here's my message: if you have electrical problems you can't solve on your own, this is the man to call.
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Old 08-04-2011
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I have been a very satisfied customer of Hamilton Ferris for many years, their ability to listen, apply their skills, and SOLVE problems is exceptional.

Someone needs to apprentice to their experts, so that all that is not lost.
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Old 08-04-2011
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Swooping in and making a recommendation, without actually discussing the great mystery problem and solution?

Makes it sound like a plant. An ad campaign.

Surely you can put some meat on that table and tell us what the mystery was.
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Old 08-04-2011
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Swooping in and making a recommendation, without actually discussing the great mystery problem and solution?

Makes it sound like a plant. An ad campaign.

Surely you can put some meat on that table and tell us what the mystery was.
I doubt Ham Ferris would do that they are an upstanding shop.

However, it would be nice to know what the big "mystery" was? Perhaps he can post what was happening here, and let us figure it out, and see if we're right...

First person to get it right wins some Gummy Bears..
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Old 08-04-2011
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1) I assure you no plant. I have a detailed write-up and in my initial post, I offered it to anyone who asks. (My purpose in posting was not to illuminate what I think is an unusual problem that I hope few would ever experience, but rather to broadcast the availability of a resource that I found head and shoulders above the others, that saved the day for me, and that others could resort to for whatever problems they might encounter. If I had gone to this guy first, rather than eight days later, I'd have saved myself a lot of hot, sweaty work, a not insignificant expense with no results, and a good deal of angst about ever getting my boat fixed.)

2) If you want to make an exercise out of it, here goes:

A) Assume a system that has been installed and working just fine for years, capable of restoring about 80+ AH of a 100 AH discharge from a day or so on the hook, in 60 minutes of engine running at 1700 RPM.

B) All of a sudden you notice that, shortly after starting engine and setting revs for 1400-1500, the tach reading drops to about 900-1000 and stays there, regardless of changes in engine RPM.

C) Next time you have big nick on the batteries, you notice that concurrent with tach drop, the alternator is putting out much less current and voltage than it should. Getting from "bulk" mode to "acceptance" mode takes way too long. However, once it gets to "acceptance," tach function resumes normal.

D) Problem grows worse; now alternator output so low that regulator will never get to "acceptance."

Pause here for first round of answers.

E) Since you have a spare regulator wired in, you switch to the spare regulator. No improvement.

F) You also have spare alternator, so you do alternator swap. No improvement.

G) Flailing around, you lift, inspect, polish, restore and torque all wire terminations, big and little. (We do this every year or so anyhow, so no surprise that they are all clean.) No improvement.

H) Really flailing around, you have the batteries (which aren't very old East Penn gels and which respond to shore-power based charging via Heart Interface as normal) tested, and you take not one, but both alternators to not one, but two qualified alternator shops for complete inspection and testing. All tests show batteries and alternators just fine. Problem persists.

I) At this point, you decide you're not as smart as you thought you were, so you bring in local marine systems outfit with great reputation. They come on board, find nothing amiss but can't solve the problem, and leave reporting selves "stumped."

J) So at this point you decide to perform the always attention-getting "full field" test: everything off, disconnect regulator from alternator, make up a #12 lead with insulated spade on one end and alligator clip on the other, attach spade to field terminal of alternator, start engine and let it settle, and clip alligator to B+ terminal of one battery. Big sparks. No improvement.

OK, who has figured it out?

Last edited by Prescinding; 08-04-2011 at 05:13 PM.
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Old 10-19-2011
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you changed the belt running the alternator..it was slipping under the higher load.
or you tightened the belt..same idea

-dkenny
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Old 10-20-2011
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Bingo; give the man a prize.

After several hours of tests, which basically ruled out any failure of any of the system components, Ham Ferris said "Let me ponder for a bit; I'll call you back." He did call back, told me to look at the belt and see if I could see my reflection. I could have combed my hair in the bright glaze. Removed the old belt; cleaned and scuffed the pulleys; and installed a new Gates Green Strip and problem fixed.

All along, what I thought was a tach anomaly wasn't: the tach was telling me quite correctly that when the regulator called for high alternator output, the alternator was slowing down. Because the belt was glazed, it didn't emit the usual telltake squeak.
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Old 10-20-2011
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Just happened to me, too. Amazing what a new belt can do. I put it on my regular list to replace list! I now buy three at a time.
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Old 11-05-2011
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Quote:
Originally Posted by Prescinding View Post
Bingo; give the man a prize.

After several hours of tests, which basically ruled out any failure of any of the system components, Ham Ferris said "Let me ponder for a bit; I'll call you back." He did call back, told me to look at the belt and see if I could see my reflection. I could have combed my hair in the bright glaze. Removed the old belt; cleaned and scuffed the pulleys; and installed a new Gates Green Strip and problem fixed.

All along, what I thought was a tach anomaly wasn't: the tach was telling me quite correctly that when the regulator called for high alternator output, the alternator was slowing down. Because the belt was glazed, it didn't emit the usual telltake squeak.
In the words of Sherlock Holmes--or somebody--once you have eliminated everything that it could be, what you have left is what it must be.

Thanks for the stumper. How many hours on the belt?
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Old 11-26-2011
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My experience over the years is that V-belt drives that don't have automatic tensioners work much worse than most people realize. Some years ago I had a commercial greenhouse customer who was planning to change out 160 1 hp fan motors to premium efficiency motors, and the power company was offering a rebate to do it. It told them I didn't think it was worth it, unless you knew a lot more about how those motors ran, and that I'd get a watt meter to test the motors before spending all that money. Surprisingly this customer bought the wattmeter and did some testing. What they learned was very surprising.

The first 1 hp motor they tested was only putting out about 1/3 Hp! They wondered if the belt was slipping, and after tightening it the motor was putting out 1 hp. A week later it had dropped to about 3/4 hp, so they changed the belt, and again got 1 hp. In another week it was putting out about 1/2 hp, and tightening it again restored the output to 1 hp. It was pretty clear that the belts, even new ones stretch, and require constant maintenance. So they install a spring loaded tensioner on the motor. It put out 1 hp, and week after week continued to put out one horsepower. They then replaced the motor with the high efficiency one. And as advertised it was about 10% more efficient. However the $15 dollar belt tensioner made the motor far more efficient, for far less cost. So they installed them on all 160 fans. The following month the electric bill fell 30%! Using the wattmeter they determined that the motors continued to put out full power with the same belt even two years later. They did buy a few high efficiency motors, as shelf spares for when a motor fails. Eliminating belt changing every year, which involved removing the guards to reach the belt was also a huge savings.

I suspect this is a much larger problem with large alternators on boats too than most people realize.

Gary H. Lucas
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