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Old 12-09-2017, 08:04   #1
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Fusing anchor light

I installed a new led anchor light last winter when my mast was down. I didn't replace the wiring in the mast because the wires appeared to be in good shape and doing so would have required removing the polymer collar attached to mast at deck level.

I could only get a couple inches of wire out of the top of the mast, but it did permit me to connect the small gauge wires from the new anchor light properly. I then pushed the wires and connectors back into the masthead.

The light worked fine until recently. When I climbed the mast to investigate (had 12v at bottom of mast) I had 12v at anchor light wires. However, when I pulled wire connectors out of masthead I saw a couple of small nicks in the insulation of the positive lead of the small anchor light wires. It must have shorted on something in the masthead, but the 5 amp circuit breaker did not trip (don't know why) and the light must have fried.

When I install the new anchor light (0.16A) I am planning on putting extra insulation on anchor light wires that will be in mast and pushing in more wire so, hopefully the additional slack will prevent chafing. I am also planning to install a waterproof fuse holder with a 0.5A fuse between anchor light and connection to wiring going down mast so if wire chafes again it will blow fuse before destroying light.

Not being an electrician I am seeking any more knowledgable opinions about this.
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Old 12-09-2017, 08:09   #2
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Re: Fusing anchor light

The shorted wires would not have fried the light. However, there are a lot of early led light failures that do occur, depending on the manufacturer of the light. Do you remember where you got the light and what brand it is?
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Old 12-09-2017, 09:14   #3
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Re: Fusing anchor light

I would temporarily connect a known-good light at the top of the mast to see if the wiring is good or not. Use clipleads or just twist some wires together as needed. I agree with Don, wires shorting should not damage the light.

It is possible that the wires have corroded where the insulation is damaged. You can still measure 12V even if the wires are badly corroded -- the voltmeter draws virtually no current through the wires. It's when you put a load on the circuit (that known-good light) that you can see how the wiring is doing.

So it's probably a bad light. Or, corroded wires.
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Old 12-09-2017, 11:22   #4
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Re: Fusing anchor light

The wire condition is fine. The wire that had the insulation scraped off was the brand new wire that is attached to the new anchor light. It is a high quality light and there is no question it is no longer functional. I don't understand how if the wire made contact with metal in the mast the breaker wouldn't trip and/or the light wouldn't be damaged.

But my biggest question now is if it is a good idea to add the 0.5A fuse between the new anchor light and the wires going down the mast and if it will better protect the new light.
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Old 12-09-2017, 12:24   #5
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Re: Fusing anchor light

Quote:
Originally Posted by GoAway View Post
I don't understand how if the wire made contact with metal in the mast the breaker wouldn't trip and/or the light wouldn't be damaged.

But my biggest question now is if it is a good idea to add the 0.5A fuse between the new anchor light and the wires going down the mast and if it will better protect the new light.
You don't say if the chafed wire was the +ve or -ve wire. If it was the +ve wire it would only trip the breaker if the mast is connected to the boat -ve bus. If it was the -ve wire then it would not trip the breaker. In either case, it could not, IMHO, cause any damage to the light. I suspect the light simply failed.

To put a fuse at your masthead, which I think is what you're suggesting, would not (once again IMHO) be a good idea. It adds no additional protection and would be an absolute pain if it did fail, for whatever reason, as you'd need to climb the mast to replace it.

Breakers and fuses are not primarily there to protect the devices at the end of the line; they are there to protect the wires (preventing a meltdown) if there is a short circuit anywhere along the line or at the device itself due to a catastrophic failure.
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Old 12-09-2017, 12:36   #6
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Re: Fusing anchor light

It was the + wire and the mast is not electrically connected to - (or +), it is only connected to keelboat and the keel is not connected to -v. Is there a way to check if mast is connected to - and I am not aware of it?
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Old 12-09-2017, 12:39   #7
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Re: Fusing anchor light

Quote:
Originally Posted by GoAway View Post
I installed a new led anchor light last winter when my mast was down. I didn't replace the wiring in the mast because the wires appeared to be in good shape and doing so would have required removing the polymer collar attached to mast at deck level.

I could only get a couple inches of wire out of the top of the mast, but it did permit me to connect the small gauge wires from the new anchor light properly. I then pushed the wires and connectors back into the masthead.

The light worked fine until recently. When I climbed the mast to investigate (had 12v at bottom of mast) I had 12v at anchor light wires. However, when I pulled wire connectors out of masthead I saw a couple of small nicks in the insulation of the positive lead of the small anchor light wires. It must have shorted on something in the masthead, but the 5 amp circuit breaker did not trip (don't know why) and the light must have fried.

When I install the new anchor light (0.16A) I am planning on putting extra insulation on anchor light wires that will be in mast and pushing in more wire so, hopefully the additional slack will prevent chafing. I am also planning to install a waterproof fuse holder with a 0.5A fuse between anchor light and connection to wiring going down mast so if wire chafes again it will blow fuse before destroying light.

Not being an electrician I am seeking any more knowledgable opinions about this.
Your logic is faulty. If the wires shorted, they would not have "fried" the light, they would have simply blown the fuse or tripped the circuit breaker. I suspect the light failed on its own because it couldn't cope with the higher voltage from the alternator or battery charger. You should buy a light with a built in constant current driver. It will be rated for 9 - 28 volts or something similar.

A fuse on top of the mast will be pretty inconvenient to check or replace. Fuses are intended to protect the wires, not the appliance (light) so your fuse should be at the point where the wiring gets its power, not at the light itself.

Your idea of extra insulation is fine. You can buy two conductor wire already in a cable with two insulated wires covered by an insulated sheath. You can also encase the cable in "wire loom".

Most important is to use bushings anywhere the wire or cable passes through an opening such as a drilled hole in a surface.

If the wires or cable simply hangs inside the mast and you have fastened anything to the mast with sheet metal screws, the pointed screws inside the mast can damage the wiring. At the very least, take them out, cut them as short as possible and round off the ends before replacing them.
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Old 12-09-2017, 12:45   #8
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Re: Fusing anchor light

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Originally Posted by GoAway View Post
It was the + wire and the mast is not electrically connected to - (or +), it is only connected to keelboat and the keel is not connected to -v. Is there a way to check if mast is connected to - and I am not aware of it?
OK, well that's why the breaker didn't trip. And that's not a problem that needs resolving. If you really wanted to check if the mast is connected to the -ve you can check with a multimeter by measuring if there is a voltage between the mast and any +ve point. But once again, it's not a problem either way.

I think you can be quite confident that the light failed for no reason that was of your making, and return it to the supplier for a replacement.
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Old 12-09-2017, 12:50   #9
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Re: Fusing anchor light

The light is rated from 10-30 volts.

I really appreciate all the feedback as I have learned a lot from it. Seems the consensus is that the light failure wasn't due to a problem with the chafed wire, but with the light itself. I will contact the manufacturer regarding this.

Thank you very much.
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Old 12-09-2017, 20:39   #10
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Re: Fusing anchor light

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It is a high quality light and there is no question it is no longer functional.
No offense intended, but have you actually connected this light (with the proper polarity) to a good 12V source and verified that it no longer works?

When troubleshooting it's really easy to make an obvious but wrong assumption that leads you in the completely wrong direction. I've done it. I still do it. We all do it. Verify assumptions!
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Old 13-09-2017, 05:05   #11
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Re: Fusing anchor light

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Originally Posted by Paul Elliott View Post
No offense intended, but have you actually connected this light (with the proper polarity) to a good 12V source and verified that it no longer works?

When troubleshooting it's really easy to make an obvious but wrong assumption that leads you in the completely wrong direction. I've done it. I still do it. We all do it. Verify assumptions!
This is a good post. Connect it directly to the battery and see what happens.

Somebody mentioned being able to measure 12 volts with a meter but not actually having 12 volts with a load applied. Those who understand electricity know how and why this can happen but in this case, it's far simpler just to connect the light to a known good power source.
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Old 13-09-2017, 06:16   #12
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Re: Fusing anchor light

Yes, I did test it once I took it down and it definitely doesn't work. The manufacturer is going to cut it open and see if he can figure out what caused it to stop working.
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