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Old 10-05-2013, 11:44   #16
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Re: Electrical question help please!

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Originally Posted by Wotname View Post
Is there a terminal connector or a switch or circuit breaker near where you are feeling the heat?

It is possible you have some unwanted resistance (corrosion etc) which is getting hot and the heat is travelling along the wire. Run your hand (carefully & slowly) along the wire in either direction to see if the temperature changes at any point.
Good thought. Check out an connections to terminal strips etc, they get oxide buildup etc and the resistance goes up.
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Old 10-05-2013, 11:58   #17
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Re: Electrical question help please!

Or maybe likely corrosion at the light bulb bases resulting in stray short-circuit current and increased current in conductors.
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Old 10-05-2013, 19:08   #18
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Re: Electrical question help please!

The bottom line is that any unexpected or unexplained warm (hot?) wire needs to be investigated.

If there is a minor fault somewhere you can be sure it will only get worse and the system will fail sometime - usually at the worst possible moment
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Old 10-05-2013, 19:22   #19
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Re: Electrical question help please!

The cheapest, simplest solution might be to convert to LED nav lights. Then, later, possibly replace the wiring. Buy yourself an infra red heat gun to measure how hot it is. This tool is incredibly useful for many other issues. Use it to measure how hot different parts of your engine get when operating normally. Then you can check those spots to see if things are ACTUALLY hotter than before.
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Old 10-05-2013, 19:26   #20
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Re: Electrical question help please!

You need to do the basics. Measure the current going through the wire and then check the wire guage tables to determine if the wire is guaged correctly for the wire guage and the run. You can get an idea of the current by adding the wattage of the bulbs and then dividing by 12 volts....which will give you amps of current.

If the wire guage is inadequate an easy but expensive solution would be to replace your existing incandescent nav light bulbs with LED nav bulbs. They can't be any LED bulbs though, they have to meet the COLREG technical specifications for nav lights and the lav light manufacturers requirements.
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Old 10-05-2013, 19:37   #21
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Re: Electrical question help please!

I bet that round trip loop is close to 50'. At 8amps would be a 6% drop for a 10 wire and over 10% for a 12 wire.

I would expect the wire to be warm.
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Old 10-05-2013, 19:48   #22
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Re: Electrical question help please!

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I bet that round trip loop is close to 50'. At 8amps would be a 6% drop for a 10 wire and over 10% for a 12 wire.

I would expect the wire to be warm.
Voltage drop will increase with wire run length, but not the temperature rise which would depend only on current flow. If fact excessive wire length will increase circuit resistance resulting in less current flow and less temperature rise. Need to consider issues that might cause higher than normal current flow instead.
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Old 10-05-2013, 20:08   #23
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Re: Electrical question help please!

I think that Wotname is on the right track, but I would not rule out the switch being the source of your problem. I got a 25 am rated switch for my water maker that draws 18 amps. That switch got so hot you couldn't touch it. The adjacent feed wire was hot as well. If I touched the feed wire 2 feet away it was cool. While the switch was rated at 25 amps it clearly could not carry 18 safely. It was of course made in the country is famous for it's quality products and now sold at ourageous prices by our favorite boating retailer in te "West".
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Old 10-05-2013, 20:12   #24
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Re: Electrical question help please!

Still though you have to confirm the circuit is not overloaded by running the numbers otherwise you are just changing out parts making a stab in the dark that it was the part.
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Old 10-05-2013, 21:08   #25
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Re: Electrical question help please!

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Originally Posted by David M View Post
You need to do the basics. Measure the current going through the wire and then check the wire guage tables to determine if the wire is guaged correctly for the wire guage and the run. You can get an idea of the current by adding the wattage of the bulbs and then dividing by 12 volts....which will give you amps of current.

If the wire guage is inadequate an easy but expensive solution would be to replace your existing incandescent nav light bulbs with LED nav bulbs. They can't be any LED bulbs though, they have to meet the COLREG technical specifications for nav lights and the lav light manufacturers requirements.
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Still though you have to confirm the circuit is not overloaded by running the numbers otherwise you are just changing out parts making a stab in the dark that it was the part.
Further to DM's good advice, after calculating the expect current, then measure the actual current.. If there is a significant discrepancy, you have a problem and that needs to sorted before going further.

As another posted suggested, excess current may indicate parallel current paths caused by corrosion in lamp fittings etc.
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Old 11-05-2013, 12:15   #26
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Re: Electrical question help please!

In the US yellow connectors are sized for 10-12AWG wires. If someone used "automotive" wire, that's more like SAE size 8-10.

The "ampacity", or safe amperage carrying capacity, of 10AWG wire is 15 amps "for power transmission". Note this is a lot lower than some some other uses. For 12AWG it is a little over 9 amps, a big difference between the two.

And with four bulbs, each possibly 10W or 20W, you've got a 40-80W load, nominally 12 volts, about 3.5-7 amps. If the bulbs are 20W and there's some added resistance in the sockets (if they weren't greased, they have corroded)...and that's 12AWG wire...you are coming close to rated capacity and can expect heat.

I'd say it is time to check the bulbs and sockets, see if the bulbs are correct and the sockets clean. That may be all it takes to cool down the wire. Or, you may want to upgrade the wire to 10AWG if the draw on the whole system is just measuring too close for a 12AWG wire.
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Old 11-05-2013, 14:10   #27
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Re: Electrical question help please!

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The "ampacity", or safe amperage carrying capacity, of 10AWG wire is 15 amps "for power transmission". Note this is a lot lower than some some other uses. For 12AWG it is a little over 9 amps, a big difference between the two.
I'm not sure what you mean by the term "for power transmission" as the only use I am aware of when using wire to supply power to a load is in fact to transmit that power. I am aware of the affect that amperage has on voltage drop when transmitting DC power, but am afraid that I don't understand this context. Do you have a reference that I can access that might explain this difference, as I would like to understand it. The references I have say that 12 awg can safely carry 45 amps and 10 can carry 60 amps. This is not to say that the wire will not get warm at these amperages, it simply means that it will not get so hot as to destroy the insulation. That is why bundling wires reduces their amperage ratings as they cannot disapate the heat as well in a bundle.
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Old 11-05-2013, 14:18   #28
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Re: Electrical question help please!

Bill, the chart I happened to grab those numbers from lists one ampacity (higher) for chassis wiring, which I presume is for short runs in a device, and another for "power transmission" which to me sounds like wire runs that will be supplying branch runs, i.e. to a breaker in a panel. Since that's in a confined space, not an engine bay run but also not out in free space, I would have to expect it to be warmer than a run in free space.

I also don't think it is dangerous, but personally I don't like to feel ANY heat coming from a wire, except the ones in my toaster.

What a wire can safely carry will depend on the quality of the insulation (varies) how well it ages (some gets brittle from age and heat), ambient temperature (bundled, free space, etc.) and to some extent, just how conservatively you want to rate it, before it becomes fusible link wire.<G>

Of course if the wire is hot that also means it is wasting power by converting it into heat. How many watt-hours of ship's power are worth upsizing one gauge of copper wire, I leave as an exercise for someone else.<G>
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Old 11-05-2013, 14:28   #29
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Re: Electrical question help please!

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Bill, the chart I happened to grab those numbers from lists one ampacity (higher) for chassis wiring, which I presume is for short runs in a device, and another for "power transmission" which to me sounds like wire runs that will be supplying branch runs, i.e. to a breaker in a panel. Since that's in a confined space, not an engine bay run but also not out in free space, I would have to expect it to be warmer than a run in free space.

I also don't think it is dangerous, but personally I don't like to feel ANY heat coming from a wire, except the ones in my toaster.

What a wire can safely carry will depend on the quality of the insulation (varies) how well it ages (some gets brittle from age and heat), ambient temperature (bundled, free space, etc.) and to some extent, just how conservatively you want to rate it, before it becomes fusible link wire.<G>

Of course if the wire is hot that also means it is wasting power by converting it into heat. How many watt-hours of ship's power are worth upsizing one gauge of copper wire, I leave as an exercise for someone else.<G>
Thanks, and I found a couple of references on Google. Learn something new every day. My guess is that almost every circuit in my boat was sized based on a 3 or 10 percent voltage drop formula, not the power transmission rating, which probably means most of my circuits are undersized or marginal at best. Food for thought, thanks again for the enlightenment.
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Old 11-05-2013, 15:50   #30
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Re: Electrical question help please!

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Originally Posted by Captain Bill View Post
Thanks, and I found a couple of references on Google. Learn something new every day. My guess is that almost every circuit in my boat was sized based on a 3 or 10 percent voltage drop formula, not the power transmission rating, which probably means most of my circuits are undersized or marginal at best. Food for thought, thanks again for the enlightenment.
If your wiring is sized to account for (3 or 10% drop) it is properly sized.
The ampacity rating of wires does not account for voltage drop, and would be higher (for a given gauge) than you would select, when accounting for voltage drop.
In other words, you'd select a larger wire size, to account for VD over distance, than just for ampacity rating.
I don't know what HS is talking about.
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