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Old 01-06-2011, 09:27   #1
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Upgrading Windlass Wiring

Hey all, our 12V 700W windlass has officially given up the ghost. Since I upgraded our ground tackle from the PO, I'm eyeballing a replacement with a 12V 1000W motor. However, the biggest impediment is the size of the existing wiring. My best guess on the length of the circuit is somewhere around 90 feet. 40' boat, battery bank near the aft end of the boat, a few turns but mostly a straight shot down the port side of the boat.

I've currently got 1/0 AWG and that looks it's just barely not big enough. 2/0 seems to be the right wire size. I'm really not looking forward to pulling 2 45ft lengths of 1/0, buying 2 45ft runs of 2/0 and running the wires all the way up the side of the boat.

What's the thinking on running multiple wires in parallel to create enough conductor to satisfy the load requirements? I presume I'm just looking for enough circular mils to satisfy the current. Does area have to exist inside a single sheath?

2/0 AWG = 133K cmil
1/0 AWG = 105K cmil
4 AWG = 41K cmil

I guess my question boils down to this: is 1/0AWG + 4AWG >= 2/0AWG ?
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Old 01-06-2011, 09:48   #2
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Re: Upgrading windlass wiring

When installing a large windlass it is common to also install a battery in the V-berth or area very near to the windlass. A Walmarts marine batter works fine and is very economical.
- - Also install a battery switch to turn power on or off to the windlass. And a bus fuse rated to the windlass so you don't start an electrical fire if the windlass solenoids jam in the on position.
- - Finally you only need a #10 or #8 wire from the main DC panel - through a dedicated C/B rated for the wire size and length - to the new windlass battery for charging the battery.
- - The advantages are eliminating the huge cost of fat copper wire led from the main distribution panel to and from the windlass. Also the removal of the potential fire hazard of the cable catching in fire should the windlass malfunction. Not to mention the hassles of trying to thread two large cables up the sidewalls.
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Old 01-06-2011, 09:55   #3
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Re: Upgrading windlass wiring

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Originally Posted by osirissail View Post
Finally you only need a #10 or #8 wire from the main DC panel - through a dedicated C/B rated for the wire size and length - to the new windlass battery for charging the battery.
I'd love to do that but I don't think I would really save much on wiring size. The way I understand it, you have to size the charging wire to that fwd battery to the size of your alternator. When the engine is running and the windlass is going, that battery is going to want all the current available to it which means the full output of the alternator is running through that charging wire. In our case, we're sizing that wiring for an 80A alternator which is a little less than the windlass draw. But the difference is probably not enough to justify installing a battery forward.
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Old 01-06-2011, 10:03   #4
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Re: Upgrading windlass wiring

I don't see a problem with multiple conductors.
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Old 01-06-2011, 10:28   #5
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Re: Upgrading Windlass Wiring

I think the forward windlass battery is a bad idea:

* The savings in weight between heavy wires vs. battery, somewhat lighter wires, breakers, heavy wire between battery and windlass, switches, battery box ... is not as much as you might think ... is just not worth it.

* You must have breakers or fuses on both ends of the charging wire.

* Weight forward is never a good idea. Wire weight in the bilge is not so bad.

* Running the engine or genset really helps get full windlass power. That won't be any help.

* Hard to justify an additional heavy battery that is very rarely used. It will probably be neglected, too.

* You really should have an extra charging regulator.

* What if it goes dead? You cannot use the house batteries to raise the anchor, and the alternator won't be any help.

* When the battery gets weak the breaker or fuses will blow.

I had such an arrangement when I bought this boat. My engineer mind said it was crazy. Tore it out. Now simpler and far better.

You are correct, all that matters is the total cross-section of the conductor, and the lengths be about the same.
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Old 01-06-2011, 10:36   #6
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Re: Upgrading Windlass Wiring

1/0 cable will handle full output of your alternator with ease. But in the battery upfront will help your winless performance. Even with 2/0 cable there will be a fair amount of voltage drop without the battery in front. And has said before don't forget proper circuit protection no matter what you do. My two cents, Mike.
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Old 01-06-2011, 10:45   #7
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Re: Upgrading Windlass Wiring

My understanding is that multiple wires are ok in theory. I also understand that multiple wires are not encouraged, as the danger of a disconnect or break of ONE wire, causes more current then initially thought to go through the other wire... leading to a meltdown or fire....

Now, the probability of having one wire disconect or break is probably low... but... as soon as one factors in the "it is on a boat" factor, and Gumperson's Law 1 then one can have a problem...

1 A summary of Gumpersons Law can be stated as: "The probability of anything happening is in inverse ratio to its desirability." But the link will explain it better....
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Old 01-06-2011, 11:07   #8
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Re: Upgrading Windlass Wiring

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My understanding is that multiple wires are ok in theory. I also understand that multiple wires are not encouraged, as the danger of a disconnect or break of ONE wire, causes more current then initially thought to go through the other wire... leading to a meltdown or fire....
You raise a good point here. If I ran a 1/0AWG wire and a 4AWG wire in parallel, I assume I would have to protect each wiring run with separate fuses sized to the particular wire to prevent exactly what you are talking about. The manufacturer calls for a 135A breaker/fuse on the circuit but if I'm running parallel conductors of 1/0AWG and 4AWG, I don't really know how to size those fuses.
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Old 01-06-2011, 11:19   #9
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Re: Upgrading Windlass Wiring

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Originally Posted by janders View Post
You raise a good point here. If I ran a 1/0AWG wire and a 4AWG wire in parallel, I assume I would have to protect each wiring run with separate fuses sized to the particular wire to prevent exactly what you are talking about. The manufacturer calls for a 135A breaker/fuse on the circuit but if I'm running parallel conductors of 1/0AWG and 4AWG, I don't really know how to size those fuses.

Find an ampacity table or someone like Gordo will chime in with the sizes but I would think you would fuse each based on wire size. So one size fiuse for the 1/0 and another for the 4.

Another thought I have had on voltage drop is that if you are running the engine while using the windlass you should be able to offset some of the drop because your alternator should be putting out something on the order of 14 volts right? So if you had say 14 volts at the batteries and a 10% drop your windlass would still be seeing 12.6 no?
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Old 01-06-2011, 11:31   #10
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Re: Upgrading Windlass Wiring

I'm not sure about fuzing the conductors separately...Seems to me they should be coupled then fuzed....I'm no expert.
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Old 01-06-2011, 11:43   #11
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Re: Upgrading Windlass Wiring

I see no problem with two wires.... other than keeping the extra connection interfaces clean and protected. You might consider just putting your new 1000w in there and testing it. run it for 30 seconds or so under load and feel the cable ends. No heat? Fugettaboutit. I've seen charter boats (years ago) with windlass cables that looked real small...nothing even near 1/0. The starter cable on your V8 car is wimpy and trying to turn a big engine over. It better start right off! I'm not saying it's the best of situations... but it might be fine.
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Old 01-06-2011, 11:44   #12
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Re: Upgrading Windlass Wiring

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I'm not sure about fuzing the conductors separately...Seems to me they should be coupled then fuzed....I'm no expert.
fusing the wires separately shall protect the wires. The sequence of events would be that first one fuse would go, then the other, as the windlass takes the current....


A sizing table for current can be had online... One source is west marine's electronic catalogue. (skip over to page 418)

here are image snips:



and
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Old 01-06-2011, 11:44   #13
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Re: Upgrading Windlass Wiring

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I'm not sure about fuzing the conductors separately...Seems to me they should be coupled then fuzed....I'm no expert.

I always thought you fused to protect the wire and as mentioned above if one of the conductors should become uncoupled you would want the remaining one to be protected. But then Im not sure about the whole practice of using multiple conductors in the first place.
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Old 01-06-2011, 11:48   #14
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Re: Upgrading Windlass Wiring

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Originally Posted by h20man View Post
fusing the wires separately shall protect the wires. The sequence of events would be that first one fuse would go, then the other, as the windlass takes the current....


A sizing table for current can be had online... One source is west marine's electronic catalogue. (skip over to page 418)

I could not find the images online, so I just pasted to my image gallery. Unfortunately I do not see how I can JUST show the image here....
so you can see the tables here: and here:

So based on that ampacity table you could go as high as 160 on the 4 and 285 on the 1/0 but if your windlass is rated lower than you probably want to fuse accordingly otherwise the wire would be protected but the windlass itself not.
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Old 01-06-2011, 12:06   #15
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Re: Upgrading Windlass Wiring

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So based on that ampacity table you could go as high as 160 on the 4 and 285 on the 1/0 but if your windlass is rated lower than you probably want to fuse accordingly otherwise the wire would be protected but the windlass itself not.
I believe one has to also look at the length of the cable...

and the second image (which I now managed to show in the post...) shows how amperage decreases over length.... 90 feet in a 4 drops down to about 13 amps....
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