Low Voltage UCL characteristics
a. The low voltage option requires a separate transformer.
b. The lights have typically lower profiles than the direct wire equivalents.
c. The bars may be cuttable unlike direct wire equivalents. This is true when low voltage LED tape lights are used.
d. The required dimmer will depend on the transformer used. If a magnetic transformer is used the dimmer needs to be a magnetic low voltage (MLV) dimmer. In small installations, a rheostatic dimmer may be used/ deployed. However, such dimmers do not save energy.
e. Most installations will be 60W or less for practical reasons.
f. The cost of the transformer(s) must be accounted for as it is typically a significant item.
g. The dimming load is (are) the transformer(s).
h. There are many vendors and a great variation in product quality and abilities (e.g. - flexibility, color rendition index or CRI, output, dimmability, wiring constraints - most are not forgiving of wiring mistakes)
i. Choices available - LED tape, bars, panels.

Direct wire UCL characteristics
a. The height is ~ 1 inch. The Philips eW profile bars are 0.88" tall, but the optional junction box could be an unwelcomed protrusion.
b. The light output could be greater than low voltage LED tape lights.
c. The dimmer for the Philips eW bars will have to be of the electronic low voltage (ELV) variant.
d. Longer runs may be possible than with the low voltage equivalents.

Common to both options
a. Having flat bottomed cabinets without intervening fences is a great advantage as you will be able to form continuous sections of illumination.
b. Separate sections of light bars should be wired in parallel so that problems in one section do not affect other sections. Consider the transformer as a simple junction box for direct wire configurations. Each section will be AC in the direct wire configuration (using romex 14/2 or 12/2)

c. There could be interesting shadow zones depending on the relative position of the bars. This typically happens in corners where the light bars should be placed perpendicular to one another rather than on the hypothenuse. There could be a shadow zone between bars that have a significant spacing between the ends.
d. If the light bars / beads of light are not to be seen reflected off the countertop, the light output should be directed towards the backsplash. An alternative could be to use edge lit light panels which really is the equivalent of aiming the light at something other than the countertop.

Hope there's enough food for thought.

The answer depends on the distance to the ceiling/ closest main reflecting surface and the amount of space to hold the light bar. If the distance is too close, the output should be lower.

If the above cabinet lighting is just for accenting some architectural features, the output from low voltage strips would suffice.

If the cabinets have intervening fences/ stiles, it may be difficult (or impossible) to form a continuous led section. Notching the cabinets is difficult once they are installed.

Corners should have the bars fitted perpendicular to each other to avoid interesting shadow zones.

The next is to decide whether to use direct wire or low voltage. This is more a logistical/ financial than technical issue as it requires selecting possible candidates and pricing out all the components involved in setting up the system.

Low voltage
If the sections are too far from the DC power supply (usually misnamed transformers) and/ or power requirement for the section too significant, additional DC power supplies may be necessary.

A thicker gauge wire may also be necessary. Many sites have a calculator for figuring out the wire gauge for a given power draw.

The cost of the transformer could be a significant component of the system which could result in the low voltage system costing more than equivalent direct wire systems

Direct Wire
eW profile is supposed to be good for up to a section as long as 50ft.
Direct wire lights are probably easier setup for installs with multiple long sections to be controlled from a single switch since there is no need to compute the wire gauge to compensate for DC voltage drop and figure out the correct power supplies.

Some reasons to use direct wire
1. High output desired for multiple sections spread out over a large area/ where low voltage equivalents could become too expensive.
2. No desire to deal with low voltage calculation, DC power supplies which need to be located in an accessible location. Or greater familiarity with AC devices.
3. Possibly better component quality (more likely for Philips eW profile) and CRI.

Reasons to use low voltage
1. Lower output. Low voltage bars have smaller conductors and/ or heat sinking that would limit the ability to drive/ over drive the LED emitters. This differentiating factor is likely to become less important as the LED emitters become more efficient.
2. Small enough install where the costs between Low voltage and Direct wire (AC) are not too dissimilar.
3. Requirement for low profile (~ 0.5")
4. Exact fit requirements, curved surfaces - low voltage tape can be cut, some bars may also be modified.
5. More vendors, more options.

Anyways - I'm a DIY'er. Needs/Constraints are:
(1) My cabinets are frameless, thus their bottoms are flush with the doors. This has highly influenced my implementation. I'm not opposed to putting up a small molding if need be, but wouldn't mind avoiding if possible. So thin is important, as well as hiding everything.
(2) Cost: Do not desire to spend $1k on lighting, so highly specialized suppliers are not an option - especially when I can find the same lights elsewhere for significantly less - of course I lose the specialized help.
(3) Dimmable: a 12 or 24V system, dimmable power supply, will put a magnetic switch in the wall (two switches, two separate run/circuits, one long, one short run across the kitchen).
(4) Would like to tile the walls in the next week (have a granite backsplash), so I do want to prep for my wallswitch, wires for my main run here quickly.

Options:
(a) Aluminum Light Bars: Common design I've seen from major or small suppliers, eBay direct from Taiwan, etc, 3/4" wide, a little less than 1/2" deep to protrude below the cabinet. Interconnects connect bars, etc. My long run (with 2 interior cabinets) is 300cm, 45W.

(b) PCB Flexible Strips: This option gets me very low profile, could get waterproof to help protect, diffuse the light slightly, options on how many LED's. In some ways, this is an inexpensive option that could easily be updated in the future if other low profile aluminum housing options appear and/or drop in price. My wires are in place, PCB installed with 3M tape.

This option has me considering putting a run on top of my cabinets - would make very nice mood lighting - but I don't really want to put another dimmable power supply in just for this - could look to use the "cheap power" options maybe for this secondary run - i.e. cheap 12/24 power supplies - but maybe reaching too far, after all I don't need to make this more complicated.

(c) Flush Mount Aluminum Housing w/PCB Strips and diffuser: This one really interests me, as it presents a rather finished look. Of course it may require me to remove some cabinet and/or run the router upside down (Ikea cabines, so they can come down if needed). It does require a 0.2" depth in the 3/4" cabinet bottom (which I'll make sure is doable before I destroy my cabinets!). My minor concern here is how the PCB mounted in the channel with diffuser will light my countertops (which BTW are a dark granite, so I'm expecting reflections). This would be a rather slick and finished looking design - of course more cost for the aluminum channels. Superbright LED's sells them for $25/100cm for the channel plus diffuser (clear or frosted?), nevermind, these are actually quite cheap!

Guess I'm just looking for David's (or other's) quick comments or thoughts on my options. My biggest quick decision is to put some wires in the wall in preparation. The open issue is gauge from the dimmable power supply to the start of my 300cm main run/circuit. Basically 2 areas separated by the stove, with two cabinet interiors mixed in. All to run off the single switch/dimmer. As I mentioned, I know it's a 45W requirement for the aluminum strips - haven't calculated for the PCB option (but will do that next).

thanks...

Measure off the wire needed - use string to estimate the lengths of each run. The environmental lights web site has a nice calculator to help figure out the gauge needed.

The power draw and wire gauge will be affected by the lights you install, length and distance from the power supply.

More power supplies could be used if necessary. Some folks managed to buy the Magnitude branded power supplies.

All of the power supplies need to be accessible.

There will be stuff on the counter top to detract from the line of light/ beads of light reflected off the countertop. Alternatively, mount the light bars so that they shine onto the backsplash (assuming a highly non-reflective backsplash). That will be an implementation of indirect lighting, so the lighting output would have to increase.

Using a router on the underside of an installed cabinet could be difficult and challenging. Uninstalling the cabinets and routing them on a bench would be more practical.

Low voltage lights are somewhat tricker.
1. Need to know the existing power draw of all the lights.
2. Voltage used - 12V or 24V.
3. Power supply - 40W, 60W,...?
4. New needs such as dimming.
5. Power draw of replacement lights.
6. Wire gauge used for existing install.
7. Length of wire sections.

If given a choice, I'd pick the Philips eW Profile.

Kitchen was gutted for the renovation. Told electrician I wanted UCL, but at the time, had no idea what kind I wanted, other than direct-wired and dimmable. He could offer no advice or suggestions. He did the wiring for 5 lights on 2 walls, all controlled by 3 switches on different sides of the room.

I purchased the Ancona LED lights from Costco (link below). He installed these for me with the basic Lutron Maestro dimmers that he used for other lights in my house. These dimmers do not work with these lights.

Do we just have the wrong dimmer? Do we also need a transformer? If so, am I looking at a lot more expense and opening up walls?

The alternative is to just use regular switches and have the ability to individually control each light bar with the on-low-high switch on the bar. Now that I have them installed, dimming might not be as important to me as I thought it would be -- especially if it would require 3 more expensive dimmers and a transformer.

The fixture is probably not dimmable given that it has a hi/lo/off switch.

It will never pay back the cost on energy.

Thanks.

I'm thinking to go with the direct wire product, so maybe it's irrelevant for me. Davidtay seems to really like the phillips eW. Maybe go with that.

Thanks for the reference to the UniLume product, David. Looks like the same technology as in the 60W replacement bulb from Phillips.

Both the eW profile and UniLume require splice boxes.

Why do you like the eW Profile better than the MaxLite direct wire solution?

Do you know any more about "HED" dimming technology from Lutron?

I see that the MaxLite actually recommends the Lutron DVCL-153P. What does that say about the integral power supply type they use? Is it electronic, magnetic, or something else?

I deduce from your comment that Philips eW Profile uses magnetic power supply? Hmm... but Philips recommends the ELV dimmer. Are ELV dimmers compatible to both electronic and magnetic power supplies? What about MLV dimmers? Or is it just NOT that simple?

These compatibility questions have dogged me for months. What type of dimmer technology is compatible to what type of drivers and why. Can anyone point me to a good online technical explanation?

Kind Regards-

The eW profile requires an elv dimmer. Most low voltage Ucl use magnetic power supplies and require magnetic low voltage dimmers.

Electronic power supplies need elv dimmers. You cannot mix and match
Most Elv dimmers work well with led.

Lutron has a nice write up

No, I've not seen the UniLume in person.

The drawbacks that UniLume addresses are primarily
1. Little glaring beads of light.
2. Multiple light sources casting multiple shadows. This effect may not always be noticeable. There are festoon light solutions for UCL which work just fine. Some have also used rope lighting without noticing the multiple shadow issue.

The first problem is very noticeable when high output LEDs are run at/ near max output over a very reflective surface.
Work arounds for both issues are -
a. Use a diffusing lens (eg - eW profile, Talea-HP )
b. Position the LEDs to indirectly light the counter top (typically the most reflective surface).

The last issue UniLume claims to solve is the limited light spread of LEDs which might be true for some LED strips, but not so for the Talea-HP, eW profile or the phonier LED bars.
From a purely technical perspective the UniLume should be a game changer, but cost considerations may eliminate it as a practical solution.

Since it is a transformer, the dimming can be done on the 120V side, which will be more convenient for my installation (I think). I'll be using multiple transformers from the same 120V regulator, to handle total power requirements.

Quite a number of low voltage installs using the environmental lights/ superbrightleds/ nora lighting/ Photonier strips (24V DC) use similar power supplies and a MLV dimmer. Others have used 12V DC.

It might be more convenient to source all the parts from 1 supplier.

The original thread (of which this is a continuation) was started with those strips in mind (even though a number of principles are universal).

I am doing a new build. I have (2) 36" uppers on one well separated by the range/hood. I have a 27" cabinet and an 18" cabinet on the other wall separated by the sink which will have a recessed light.

I looked at the Philips ew lights but they only come in 9", 19", and 39" so I wouldn't have a good fit for my 36" cabinets.

I saw these from Costco mentioned earlier. I guess I could do (2) 14" bars per 36" space. I don't really care if they are dimmable or not.

But I'm completely unable to really tell if this will work or not...???

The main point is whether the bars will produce enough light. Using a measure such as lumens (for example) instead of measuring the light output by watts would be a better means of determining whether the lights would be usable.

Environmentallights and other websites do have charts that help illustrate the light output with distance and illumination angle.

If you expect to use the UCL alone without any other light sources, the bars should be capable of producing > 200 lumens per ft (very rough guess without bothering about distances).

With the UniLume (~ 600 lumens per ft), you'd most likely have them dimmed.