Three Questions: Relating to Pond Lights, Transformers and Enclosed Fixtures

I am new to LEDs. Other than flashlights, I have replaced several light bulbs with LEDs, as well replaced all my under-cabinet pucks with Cree LED ones.

Now I have a few questions to which I have not been able to find answers:

1. I am redoing my koi pond, which underwater light fixtures built into the walls, each using a 50W halogen floodlight (130v).

I am wondering if I can replace the halogen bulbs with LED ones? Is the fact that the fixtures are underwater going to provide enough cooling to alleviate the enclosed fixture problem?

2. The second question is similarly relating to enclosed fixtures. I have a few globes, a couple of 18" plastic ones, as well as smaller glass ones, varying in diameter between 10" to 15". They are enclosed, but there is some air in the globes, particularly the larger ones.

Do you think these globes would provide sufficient cooling for LED bulbs? Or, are there any LED solutions which can deal better with the heat?

3. Finally, as I mentioned above, I have replaced 5 halogen pucks with Cree LED ones (like these Link removed.

They worked great for a few days, but last night I turned them on and there was suddenly a lot of buzzing, as well as flickering. This morning most of it was gone, but if I get close to the fixture, I can still hear the buzzing.

I am using a 150W transformer, which outputs 11.7V and was powering the halogen pucks for about 10 years. Any ideas as to why the LEDs would suddenly go crazy?

Thanks!

Thanks for approving and editing the post, Bullzeyebill. I am definitely not shilling: I posted the link just in case these particular LED pucks are known by others to buzz. (Not much of a shill to say that a product starts buzzing and flickering less than a week after installation....

I guess mu question was: Is there anything particular which would cause such buzzing and flickering? The power supply has worked for years with halogens, so it should be fine for the LEDs too, right?

Oh, and with regards to the enclosed fixtures, how much does the accumulated heat shorten the life of the LEDs? I suppose it's a lot, but does it kill the LEDs in a month, or does it take years?

Hi, again.

Nobody has an insights?

As long as there is some type of heat transfer from the "LED heatsink housing surround" to the water, it should work fine.

If you're using 50w halogens, you'll probably need 15-20w of LED to be equivalent which should also help.

LEDs need clean electricity. More then likely, you cooked them with a surge of some kind. You want to use a fixed current power supply for LEDs. And, I do recommend surge protection, like what you use for your LCD-TV, computer, home stereo.... for ANYTHING powering an LED.

Some types of transformers have minimum load requirements too. I am guessing this is a landscape lighting transformer? It outputs AC?

Thanks!

The transformer is from B+L Technologies, model CV90021 (found its specs here: http://www.bulbtronics.com/Search-The-Warehouse/ProductDetail.aspx?pid=BTCV90021 &sid=0048613)

It's electronic and it was working fine with the halogens before (for about 10 years). Also, I do have a whole-house surge protector, which I put in after all my appliances got fried a few years ago, when lightning struck a transformer 300 yards away.

O.K., I seem to have figured out the flickering issue: it was the electronic transformer. Just placed an order for a new one, specifically for LED (fixed current supply, as deadrx7conv noted), so hopefully it will take care of the buzzing and flickering.

deadrx7conv said:

As long as there is some type of heat transfer from the "LED heatsink housing surround" to the water, it should work fine.

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I took out the lights from the pond, they are 4" Pentair ones and 12v, as it turns out. The bulbs are actually 75W halogens, but I don't need them that strong. The bulb just sits in the middle of the sealed light fixture, though -- would the water cooling off the fixture be enough of a heat transfer for LED MR16 bulbs, or is it a no go?

Zup said:

...The bulb just sits in the middle of the sealed light fixture, though -- would the water cooling off the fixture be enough of a heat transfer for LED MR16 bulbs, or is it a no go?

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What can I use to transfer the heat from the bulb to the fixture's walls?

I was thinking of brass wool, but it seems it's flammable and it can cause shorts.

The LED needs to be on a heatsink that is snug inside the housing.