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Old 09-03-2011, 02:34   #16
mrm
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Re: Engine compartment light suggestion

Quote:
Originally Posted by Extemporaneous View Post
Surely this is a relative thing. I have an led 12 Volt work light that has spent much time in the heat. So far so good. I know what I've just said is not scientific, but........

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Extemp.
Sure, as with most things in engineering, there is a compromise somewhere.
The reasoning is:

  1. to maintain spec on LED lifetime, manufacturers recommend _die_ temperature should be kept below 80C (or thereabouts) when LED is ON;
  2. power LEDs designed for lighting applications are relatively expensive, so there is a tendency to use fewer LEDs in a lamp and drive them with a current close to mfg spec limit. For example, a single power led may be driven at 1.5A which will produce ~5W heat. This heat must be dissipated to the outside of LED light;
  3. heat can only be dissipated (conducted away) if there is a negative temperature gradient between LED and its surroundings;
  4. each LED element has a specific thermal resistance [deg C / W] plus there is a thermal resistance of the light housing. For a good example have a look at Cree specs for their XLamp XP-G series of LEDs ( http://cree.com/products/pdf/XLampXP-G.pdf ). Cree specifies 6 deg C / W for this LED.
Combining points 2,3,4 it can be calculated, that to satisfy point 1 and keep the LED die happy and cool the temperature of the light enclosure (acting as a radiator) should not be higher than 80[C] - 5[W]*6[C/W] = 50C

Estimate of a lamp surface area needed to maintain this requirement inside engine room (and a possibility of this) is left as an excercise to the reader

On the other hand, engine room light will likely be OFF for 99.9% of the lifetime of a boat, so we may throw all calculations out of the window and be happy with much shorter life of a LED lamp there.

Regards,
Marius
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Old 09-03-2011, 10:36   #17
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Re: Engine compartment light suggestion

So what your saying is that LED's have to deal with and live with all of the same things that cause grief to the other lighting types.

Also....... "LED Lights have the benefit of a super long life span of up to 40,000 hours which means you can cut maintainance costs as the lamps last up to 8-10 times longer than standard halogen lamps making them an ideal replacement." (Taken from the Web). So it's very much a relative thing.

Cheers,
Extemp.
Quote:
Originally Posted by mrm View Post
Sure, as with most things in engineering, there is a compromise somewhere.
The reasoning is:

  1. to maintain spec on LED lifetime, manufacturers recommend _die_ temperature should be kept below 80C (or thereabouts) when LED is ON;
  2. power LEDs designed for lighting applications are relatively expensive, so there is a tendency to use fewer LEDs in a lamp and drive them with a current close to mfg spec limit. For example, a single power led may be driven at 1.5A which will produce ~5W heat. This heat must be dissipated to the outside of LED light;
  3. heat can only be dissipated (conducted away) if there is a negative temperature gradient between LED and its surroundings;
  4. each LED element has a specific thermal resistance [deg C / W] plus there is a thermal resistance of the light housing. For a good example have a look at Cree specs for their XLamp XP-G series of LEDs ( http://cree.com/products/pdf/XLampXP-G.pdf ). Cree specifies 6 deg C / W for this LED.
Combining points 2,3,4 it can be calculated, that to satisfy point 1 and keep the LED die happy and cool the temperature of the light enclosure (acting as a radiator) should not be higher than 80[C] - 5[W]*6[C/W] = 50C

Estimate of a lamp surface area needed to maintain this requirement inside engine room (and a possibility of this) is left as an excercise to the reader

On the other hand, engine room light will likely be OFF for 99.9% of the lifetime of a boat, so we may throw all calculations out of the window and be happy with much shorter life of a LED lamp there.

Regards,
Marius
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Old 09-03-2011, 10:44   #18
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Re: Engine compartment light suggestion

I've been very happy with several purchases both for boat and house from these guys:

LEDs - underbody kits, cathodes, flexible LED strips, dome lights

If they can make lights which go UNDER cars, I think they'd survive an engine compartment!
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Old 09-03-2011, 11:01   #19
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Re: Engine compartment light suggestion

Quote:
Originally Posted by Extemporaneous View Post
So what your saying is that LED's have to deal with and live with all of the same things that cause grief to the other lighting types.
Well... no. In fact, I was trying to say something quite to the contrary. Where standard incandescent light bulbs will be happy (hot environment), LEDs may have a hard time operating for long. But it seems I have poor communication skills

Quote:
Also....... "LED Lights have the benefit of a super long life span of up to 40,000 hours which means you can cut maintainance costs as the lamps last up to 8-10 times longer than standard halogen lamps making them an ideal replacement." (Taken from the Web). So it's very much a relative thing.
And this web quote, taken out of bigger context, is nothing but a marketspeak (this remark is not aimed at you personally). There is quite a number of engineering constraints which must be met to make this statement true. Meeting those constraints is sometimes neither easy, nor cheap...

But, as I said, it is likely that engine room lights will be off for 99.9% of a boat's lifetime, so nobody will probably notice anything anyway. And, yes, other light sources have their own set of problems to cope with. Just mostly different than LEDs.
Let's rest this case.

Greetings,
Marius
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Old 09-03-2011, 11:25   #20
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Re: Engine compartment light suggestion

As we have a CC, I installed 2-4' florescent fixtures on the ceiling of our engine room.
Them being on the ceiling they put out good light with no shadows.
FWIW
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Old 09-03-2011, 11:34   #21
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Re: Engine compartment light suggestion

If you want cheap, watertight, rugged, reliable, 12 volts and don't care about efficiency, then these work. I have had four in my engine space for many years. The bulbs are twelve volts with a standard size light bulb socket that are cheap and easy to find. I put a little silicon grease on the socket so they do not seize up. The lens is glass and not cheap plastic that is eventually going to fog up. Not showing is a switch on the other side.

If you want to wire in 120, you could even get fancy and put an LED or halogen bulb with a standard sized socket in there. Home Depot has them. Beats paying through the nose for the yachtie bulbs.

http://search.defender.com/search.as...+caged&x=0&y=0


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Old 09-03-2011, 11:54   #22
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Re: Engine compartment light suggestion

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Originally Posted by Unicorn Dreams View Post
As we have a CC, I installed 2-4' florescent fixtures on the ceiling of our engine room.
Them being on the ceiling they put out good light with no shadows.
FWIW

Thats interesting, what did you use for fixtures? I would hate to clean up the engine room from a broken flourescent tube breakage.
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Old 09-03-2011, 12:28   #23
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Re: Engine compartment light suggestion

Just used standard dixtures, they come with translucent covers.
So I guess if you hit one with a hammer and some how manage to break the bulb, the glass of the bulb would stay in the fixture.

Have never had one break yet.
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Old 09-03-2011, 12:30   #24
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Re: Engine compartment light suggestion

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Just used standard dixtures, they come with translucent covers.
So I guess if you hit one with a hammer and some how manage to break the bulb, the glass of the bulb would stay in the fixture.

Have never had one break yet.

Are these 12VDC? If so can you show me where to buy?
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Old 09-03-2011, 12:47   #25
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Re: Engine compartment light suggestion

They are 110V, but you can use an inverter to make them work.

That could be a disadvantage if you don't have an inverter or generator when at sea, otherwise shore power. I try not to go into my engine room at sea unless absolutely essential.
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Old 09-03-2011, 13:11   #26
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Re: Engine compartment light suggestion

Or, if you know which end of the soldering iron is which you may take the 110/230V fixture, gut it from factory ballast/starter and roll your own 12V supply ( Lighting and LEDs ). Not really difficult, but takes some time.
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Old 09-03-2011, 18:31   #27
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Re: Engine compartment light suggestion

Quote:
Originally Posted by David M View Post
If you want cheap, watertight, rugged, reliable, 12 volts and don't care about efficiency, then these work. I have had four in my engine space for many years. The bulbs are twelve volts with a standard size light bulb socket that are cheap and easy to find. I put a little silicon grease on the socket so they do not seize up. The lens is glass and not cheap plastic that is eventually going to fog up. Not showing is a switch on the other side.

If you want to wire in 120, you could even get fancy and put an LED or halogen bulb with a standard sized socket in there. Home Depot has them. Beats paying through the nose for the yachtie bulbs.

Defender.com Search Results: light caged


x2

installed the light.. works great..nice quality
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Old 16-03-2011, 08:53   #28
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Re: Engine Compartment Light Suggestion

It appears that the LeD saga is not finished. The 40,ooo claimed hours of life, (lets say 5 years) and low consumption make it sound like a great deal. However, our boat has incandescents older than that are still operating and for the cost of converting the entire system to LeD we could buy a lot of fuel for our genset. For all intent and purpose, I see no extenuating value by switching out perfectly good fixtures for apparently questionable technology (ie RF interference both emission as well as susceptibility to immissions, heat stress and voltage variable resilience) regardless of manufacture's claims. If it ain't broke, don't fix it.
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Old 16-03-2011, 09:32   #29
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Re: Engine Compartment Light Suggestion

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It appears that the LeD saga is not finished. The 40,ooo claimed hours of life, (lets say 5 years) and low consumption make it sound like a great deal. However, our boat has incandescents older than that are still operating and for the cost of converting the entire system to LeD we could buy a lot of fuel for our genset. For all intent and purpose, I see no extenuating value by switching out perfectly good fixtures for apparently questionable technology (ie RF interference both emission as well as susceptibility to immissions, heat stress and voltage variable resilience) regardless of manufacture's claims. If it ain't broke, don't fix it.

Sorry but I think you are out to lunch on this. LED bulb conversions even the really nice sensibulb ones are $30 and draw next to nothing. They also dont give off all the heat (wasted energy) that halogens do. Im not sure how many cabin lights you have or what % of your dailiy energy consumption goes to lights but I can tell you its made a huge energy savings on my boat. But if you want to keep running your genset to keep up with your cabin lights I say go for it just do me a favor and run the genset in another anchorage.
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Old 16-03-2011, 09:58   #30
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Re: Engine Compartment Light Suggestion

SV Escape Plan,

I am with you all the way. Did he say he would rather run the generator than replace a regular 10 watt bulb with a 1 watt LED.
Wow.
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