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Factory harness, complete with molex-type connectors to plug in options from the factory. There was only 1 10-gauge SAE-rated main run from batteries to helm, a 50 foot round-trip run. This main was connected to a 15 position switch panel.
My complaints: SAE wire doesn't carry same current as AWG-rated wire and the wire is NOT tinned. #10 wire will only carry about 7 amps that distance at a 3% loss. Yet, the panel has switches and is labeled for 2 wipers, windlass, yada yada ... in addition to the usual nav/anchor light, cockpit and deck lights, etc.
Is it me or is this extremely poor ? What are your thoughts or what have you found??
In a few weeks I'll be "surveying" a friend's new Steiger ... will be very interesting to see what they did. I will say that they asked him what he plans to run and possibly add ... that's a good sign.
The calculation is the wire size in circular mills (which equates to just how much current/ampacity the AWG wire can handle at the desire voltage drop) is:
CM = [K x Amps X (Wire Run X 2)] / voltage drop
Where K is a constant of 10.75. This is a 25' run, so it's 50' total back and forth and I'm no electrical engineer but you MUST factor in the run both ways, even though there is a separate wire running each way. (Why? I dunno ... ) The voltage drop for critical items like radios and pumps is 3% or (12 volts X 0.03) = 0.36.
Here's my equation:
CM = 10.75 X 7 X (25' X 2)] / 0.36 , making CM = 10,451 circular mills, which is closest to the rating for a #10 AWG wire.
Got it??
Gerg:
This was on a '92 vintage SPort Cabin. Nice and clean job, but ... On newer ones there is a run similar to what you described , thankfully for you !
The reason for using 2 times the run distance is because the same current flows in both wires, and both wires will have a voltage drop. You want the total voltage drop of both wires to be less than 3%.
This is only true if both wires do indeed have the same run length. Thom has shown on his boat he has several instances where the run length of the negative wire is much shorter than the positive wire. So by using the 2 times the run distance he could end up with a larger than necessary gauge of wire.
It's in great shape overall, I've only had to replace the trim tab pump and the nav lights. That and clean up connections and aftermarket runs. The rest of the work has been adding new stuff. I am very pleasantly surprised at the lack of refurb I've needed to do. They really build these things well.
Sad, isn't it? My CC had the same 10 ga. wire as the main feed to EVERYTHING (pumps, lights, electronics)at the helm. If that wasn't bad enough, I discovered they (the factory) had spliced in a fuse holder at the battery. Although it was fused at 20amps, the in-line fuse holder was spliced in with butt connectors (not sealed), and it had only 18ga wire. Needless to say, I immediately ran a 8AWG feed and ground, with a separate CB at the console, all solder connections. The original wiring remains as a "get home" redundant system. The result: brighter lights, more efficient pumps, and peace of mind.
But I do have a question. Is the10AWG wire in the boat different that #10 wire for your home? I believe that stoves, dryers, and other current demanding devices are wired with #10 wire. The home wire is solid, not stranded tho. Those units draw more than 7 amps running, prob close to 15 to 25 amps AC. Just curious about the dif.
Also, my opinion about the reason manufact and dealers use the smallest wire they can is $$. When I wire my boat accessories, I use the largest wire that will work that I can run within reason.
You guys are beginning to get me a bit concerned. I've owned boats for 25 years and never gave this stuff much thought. Never had any problems either despite my total ignorance! Anyway, I don't know the gauge of the wire in the main run in my new Parker but it's about as thick as a standard pencil. All the connections on the switch panel are the spade type and there are in-line fuses bundled into the harness which comes up into the console. Are we thinking that the main feed and spade connectors should all be upgraded??? I've sent an e-mail to Parker to try and find out what the existing load might be and what the capacity of the existing wire is. Atleast I'll be able to find out if I can use the spare connections on the existing fuse block (for electronics) or if I have to install a new circuit from the battery switch. UGH!
reel-rascals,
The capacity of the 10 ga wire with 50' round trip run is about 24 amps. Figure it this way:
V = IR where V is the allowable voltage drop, I is the current in amps and R is resistance in ohms. Then 12v with allowable 10% drop = 1.2V
R = .999 ohms/ 1000' of wire therefore 50' of wire has .05 ohms resistance. I = 1.2/0.05 then
I = 24amps. Probably not too bad for the normal load on your electronics. You can add up the max draw of your equipment and if it is less than 24 amps, you're O.K.
Check out that load before you worry too much.
Joe
With all due respect, you used a completely different voltage drop value than I did . Use "0.36" (3% voltage drop as I said) divided by 0.05 for the resistance and you get 7.2 amps.
Why would I want to fool around with a main run that may have a VHF (6 amps transmitting), running/nav lights (2-3 amps depending on bulbs), plus who know what else on the circuit?
Per every boat electrical standard out there, you should PLAN for only a 3% voltage drop on crtitical items. Sorry, but pumps, nav lights, VHF, depth, and GPS are right up there on my list of critical items !
The point I was making, and you may have missed it, was that this entire boat was rigged with 1 run only of #10 SAE wire, which has less ampacity than AWG. And as rigged this had 2 bilge pumps, washdown (10 amps), full lights, 3 cabin/deck lights, all electronincs including radar, and a fancy switch block on the dash for 15 curcuits. No wonder the previous owner thought the performance from his electronics was "marginal".
If you want to run your boat and critical items assuming you'll squeek 24 amps out of that sinlge #10 run and have fool-proof performance ... hey, go ahead. #10 wire will only carry about 7 amps that distance at a 3% loss. I think it would be foolish ... .
Reel,
You're right, My old brain zipped right past the ASE. 3% hoever, is a small margin to judge an existing system by. New installation, that's another story. I would be almost more concerned that it's not tinned wire. He can add his load up and find out where he is on the loss. Looking back at his boat size, more than likely the wire will be too small. If it were mine, I'd replace the wire just because it's not tinned. One season in salt water can really screw with un-tinned wire.
Joe
Factory Wiring Harnesses ... what the ... ?? 
? What are your thoughts or what have you found??
! 
. Use "0.36" (3% voltage drop as I said) divided by 0.05 for the resistance and you get 7.2 amps.
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