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Old 09-22-2013, 12:48 PM
TigerElectrical TigerElectrical is offline
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Design, Wiring & Bulb Installation

As I mentioned in another thread I'm taking over an incomplete year-old installation of LED lighting. I haven't done LED before and have questions regarding best practices, acceptable practices and poor practices.

Is it not necessary to do hub wiring with LEDs to maintain an even voltage throughout the installation? This installation appears to be strung, if that's the term. The connections are made with wire nuts, above grade in one place. In line-voltage wiring a set-screw connection with shrink tube is required. And the bulbs were installed with what appears to be no-alox. I'm guessing that the fixture and bulb pin are plated steel (not aluminum) and copper grease might be a better material. But then what do I know?
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Old 09-22-2013, 02:10 PM
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In LED, the hub is not really relevant anymore. I still however, group my fixtures in a hub not because of voltage drop, but more for convenience. I still like to keep my home run cables tight to the foundation and not through the middle of flower beds where they can potentially be cut. If I run my long 25' lead wires back to a "hub", I have fewer connection points to fail and fewer connections to eat up the clock. You will just need to meter the 1st and last connections to make sure you are in your operating window for the LED's you are using (which is usually between 9-15 volts).

I use buchanan, barrel crimps on all of my connections so they stay tight. I then put them in a "sure-splice" DBY to protect them. You can use heat shrink too if you like (I used to for inground), but they take longer and I am all about getting it done quickly and competently.

It's really pretty simple now that everything has gone to LED. It is so much more forgiving.
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Old 09-22-2013, 02:54 PM
steveparrott steveparrott is online now
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Quote:
Originally Posted by TigerElectrical View Post
As I mentioned in another thread I'm taking over an incomplete year-old installation of LED lighting. I haven't done LED before and have questions regarding best practices, acceptable practices and poor practices.

Is it not necessary to do hub wiring with LEDs to maintain an even voltage throughout the installation? This installation appears to be strung, if that's the term. The connections are made with wire nuts, above grade in one place. In line-voltage wiring a set-screw connection with shrink tube is required. And the bulbs were installed with what appears to be no-alox. I'm guessing that the fixture and bulb pin are plated steel (not aluminum) and copper grease might be a better material. But then what do I know?
I agree with Tim's comments regarding hub and connectors.

A couple other things - connections made above grade are not OK, all wiring should be buried a min. of 6 in. in most situations. Refer to NEC for burial guidelines under sidewalks, driveways, etc.

The best grease to reduce pin corrosion and maintain conductivity is Sanchem NO-OX - this is a conductive grease and should be used very sparingly - just a thin coat on the pins.
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Old 09-22-2013, 03:40 PM
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JimLewis JimLewis is offline
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I don't disagree with any of the advice above. All good stuff. Especially on the connections.

As for the issue you're explaining with hubs vs. daisy chain (what you called "strung") that is a little more complicated issue. In general, you don't have to worry about voltage drop issues with LED fixtures, because many fixtures have a wider threshold that they will illuminate in. So making sure each fixture gets the exact same voltage (or close) isn't nearly as important as it used to be with fixtures that had halogen or incandescent lamps.

But that said, it depends a lot on which brand you use what that threshold is. Some brands only illuminate fully in the 12-15 volt range. So you still have to watch your voltage to make sure each fixture gets at least 12. And if you're using a transformer who's biggest tap is 12 volts, you're going to have problems. Once you start getting much under 12v, a lot of the fixtures on the market start to decrease in illumination, like the older halogen/incandescent fixtures did. But other brands will illuminate fully all the way down to 8v. So you really need to understand what the thresholds of your fixtures are and keep the voltage high enough to make sure they get full illumination.

Also, some fixtures have built in voltage-regulators (if that's even the right term) that keep the voltage at a certain point, even if you over-volt. So that helps keep the lifespan of the lamp long. But other fixtures do not, so you need to be careful not to over-volt those ones.

Some brands still encourage using the hub system, because their LED fixtures still have a pretty tight voltage range that needs to be maintained. So getting to know the brand you're using and what the manufacturer recommends regarding hubs/voltage range, etc. is important.

I prefer to daisy chain and I like to use fixtures with the widest voltage range possible. It just makes the installation process much easier for my workers, who don't always understand as much about lighting as I do. So there is more forgiveness in a system that has a wide voltage range and where you can daisy chain for long lengths. Less can go wrong. But everyone has different tastes. The thing is, just learn from your manufacturer's rep. what the recommendations are for that brand of LED fixtures.
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Old 09-22-2013, 06:33 PM
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Jim, What LED brands do you know of that require at least 12 volts for full illumination?
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Old 09-22-2013, 09:52 PM
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JimLewis JimLewis is offline
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Quote:
Originally Posted by starry night View Post
Jim, What LED brands do you know of that require at least 12 volts for full illumination?
I've seen demonstrations at the IA show and several local expos/shows that show 4 or 5 different brands of LED fixtures all lined up in a row, hooked up to a power supply with a dial on it, similar to the one below. And when the dial started to get turned down a little below 12, some of the fixtures would start to fade. Once it got below 11, you'd see them fade more. Below 10 and most of them were over half of the full illumination. At 9 most of them were off or so faded they didn't really illuminate much of anything.

I have a Protek DC Power Supply Model #3006B. I use it for testing fixtures like that. I just now did a test on an FX Luminaire JubileBijou that I had out in my garage (see photo below). Once I got down to about 11.3, I could start to see the light output flicker (probably the internal voltage regulator adjusting) and I could see output decrease a little. Once I got to 10.5 then it really began to fade from that point on. Once I was under 10 it faded by about half.

I've seen this at varying degrees with different fixtures. I should probably buy one of every brand they sell locally and document the point at which they all start to fade. But I'm not trying to start an argument here. Maybe it's 12v, maybe it's 11. My only point is they do all start to fade or go off at a certain point. Some brands stay at full power for much lower voltage than others. And if you aren't paying attention to what point the fixtures you install start to fade, and just daisy chain the entire system without really bothering to check this, you're may find yourself in trouble with some LED fixtures out on the market. In those cases, it probably would be a good idea to continue using the hub system. In the case with FX, I could notice a big difference between 12v and 10.5. So that's a pretty small range. If you're using a transformer that only had a 12v tap, you'd have to be very careful.

Now if you're using multi-tap transformers and starting with 15v, then you have a pretty big range to work with. You can daisy chain for much further. But if not, it is something you still have to consider.

I'll buy some other fixtures and see what I get with the others. I was pretty sure I saw some start to fade at just under 12. But I could be wrong.
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Old 09-22-2013, 10:31 PM
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Thanks Jim, That was some good insight to share with those who may not be as familiar with the different brands out there. A good word of caution to check what you are installing.
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Old 09-22-2013, 10:42 PM
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starry night starry night is offline
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If my question sounded like a challenge, Jim, it wasn't. It was purely seeking information. Although you can daisy chain with LEDs more than you can with halogen, I personally try to balance the voltage to some extent. It just seems like a good practice that doesn't take much extra time or effort. And a little check with the voltmeter confirms the limits.
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Old 09-22-2013, 10:55 PM
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JimLewis JimLewis is offline
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No. I didn't take it that way. I was just trying to back up my previous statement. I can give more specific info. later. I may make a separate thread for it.

I agree. Good idea to somewhat normalize the voltage to a certain extent. I can do that without using hubs most of the time. But it's good to know how far you can take it if you have to, or it's not convenient to do it another way.
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Old 09-23-2013, 09:40 AM
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Here is a related thread from last year:

http://www.lawnsite.com/showthread.p...ht=led+drivers
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