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Guru
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Require Help/advice Regarding Led Lighting Choice Solution

06/15/2011 9:17 AM

I hope that this CR4 Section is the correct venue to ask for help & advice regarding the selection of the proper LED bulb for installation in our kitchen remodelling project. The new LED bulbs will be installed in the appropriate fully-adjustable light heads suspended from ceiling-mounted linear tracks over our standard kitchen countertops found along the walls and over a centrally located kitchen "island". I also have a few questions that require clarification. I am not an Electrical/Illumination Engineer, so please keep that in mind and be gentle....

We have a preliminary choice of LED bulb, as follows: PAR30 R30 BR30 LED CREE, 120 VAC, 60 Hz, 8W, 650 Lumens max., either Warm White (3000 K) or Daylight White> 5000 K60 degree light beam cone, G70, E27 Edison Standard screw socket, and dimmable (with appropriate new dimmer, which we will purchase). Other Existing Factors: Sloped ceiling, ranging from 7'-2" to 9'-2" AFF. The majority of the proposed ceiling-mounted tacks will be parallel to this sloped ceiling. The countertop surfaces are 36" AFF. Other: I have found the appropriate calculator (and formulas) on the International Light Technologies website (via the toolbox here and old CR4 postings) that will determine the generated light intensity once the known information is inputted: the bulb intensity output, light beam angle (cone) and 2 known distances, so there's no need to give me that info. Q #1: What would be the recommended light intensity value on the countertops that Architects and Illumination Engineers would use? My wife and I would prefer that the light intensity be high, but not blinding, so that we can see what we are preparing and not cut-off our fingers with very sharp cutlery! Is there a national standard to follow? We prefer Daylight White color over Warm White color. Currently, the lighting situation is abhorrent, with only 2 standard 60W Edison bulbs; that is, other than the presence of the 2 - 40W range hood bulbs...... Q #2: I've tried to find this on the www (for verification purposes), but when a LED bulb manufacturer states a certain light intensity for the bulb where is that intensity measured in relation to the face of the bulb? Is it measured 1 foot away from the surface? In the USA is that intensity measured in Lumens/ Sq. Ft., or is it Lumens / meter^2? If not, what are the appropriate units of measure? I do have the Engineer's pocket reference book to do the necessary units conversions if needed...No prob! Q #3: To reduce "shadowing" effects on the illuminated surface (such as my kitchen countertops), what percentage of the illumination diameter (@ the surface) is generally required in the overlapping areas? 10%, 15%, 20%, 25%, or 30% etc etc of overlapping illumination diameters? What is/are the industry standard(s) that Architects and Illumination Engineers utilize? Remember, I will be installing these bulbs linearly. I ask this because I'm trying to get a real sense, or grip, on the minimum required quantity of LED bulbs, and hence the number of light heads and quantity of track I need to purchase. Gotta fit the budgetary constraints ya know! :-) Anyhows, I can adjust the light head & bulb spacings during the installation of the lighting system to get the desired effect. Q #4: Generally and in layman's terms, what are the main differences between PAR16, PAR20, PAR30, and PAR38 except the costs? I've tried to research this online and haven't come up with enough information to answer my question. Thanks in advance for any assistance the CR4 crowd can provide to this clueless Civil Engineer! Maybe now my sweet wife will stop "barking" at me to find solutions to the "lighting question"! LOL Like I already don't have enough to do in regard to the "HONEY DO LIST", eh?! Please have a great sunny day!

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Anonymous Poster #1
#1

Re: REQUIRE HELP/ADVICE REGARDING LED LIGHTING CHOICE SOLUTION

06/15/2011 9:47 AM

last Question - what are the main differences between PAR16, PAR20, PAR30, and PAR38 except the costs?

PAR = Parabolic Aluminium Reflector

The number = Diameter of the Reflector (Bell) in inches x 8

ie PAr 16 = 2" Parabolic Aluminium Reflector

Did you by chance come across 2.1 in this?

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Anonymous Poster #1
#2

Re: Require Help/advice Regarding Led Lighting Choice Solution

06/15/2011 10:10 AM

The question is so long that I am reading in bits and replying

when a LED bulb manufacturer states a certain light intensity for the bulb where is that intensity measured in relation to the face of the bulb? Is it measured 1 foot away from the surface?

If the manufacturer specifies lumens (which it will usually) then it is the total power output. The illumination obviously be depending upon the distance in lux (Lumens/ sq meter)

For good lighting I would say about 500 Lux is good. But may be at countertop it will be higher say 700-750.

Based on that you can calculate the lumens on the kitchen table (the cone angle and the distance will give you the coverage section area) x 500 will be the lumens requirement. There is another link here on this

Another good article about lighting (three layers of lighting)

The question is so long that I am reading in bits and replying

when a LED bulb manufacturer states a certain light intensity for the bulb where is that intensity measured in relation to the face of the bulb? Is it measured 1 foot away from the surface?

If the manufacturer specifies lumens (which it will usually) then it is the total power output. The illumination obviously be depending upon the distance in lux (Lumens/ sq meter)

For good lighting I would say about 500 Lux is good. But may be at countertop it will be higher say 700-750.

Based on that you can calculate the lumens on the kitchen table (the cone angle and the distance will give you the coverage section area) x 500 will be the lumens requirement. There is another link here on this

Another good article about lighting (three layers of lighting)

The question is so long that I am reading in bits and replying

when a LED bulb manufacturer states a certain light intensity for the bulb where is that intensity measured in relation to the face of the bulb? Is it measured 1 foot away from the surface?

If the manufacturer specifies lumens (which it will usually) then it is the total power output. The illumination obviously be depending upon the distance in lux (Lumens/ sq meter)

For good lighting I would say about 500 Lux is good. But may be at countertop it will be higher say 700-750.

Based on that you can calculate the lumens on the kitchen table (the cone angle and the distance will give you the coverage section area) x 500 will be the lumens requirement. There is another link here on this

Another good article about lighting (three layers of lighting)

http://fleamarket.about.com/od/decoratelikeapro/ss/interiorlightingdesignbasics.htm

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Guru
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#3

Re: Require Help/advice Regarding Led Lighting Choice Solution

06/15/2011 9:03 PM

Q #1: What would be the recommended light intensity value on the countertops that Architects and Illumination Engineers would use?

Living rooms are often around 50 lux. Kitchens and other work spaces are often about 10 times that. If you want it really bright, figure on 600 lux. You can use dimmers to keep the lamps at 75% of full brightness. This will prolong the life of the lamps and as the LEDs age allows you the ability to compensate.

It's very difficult, though, to calculate the net lighting at the countertops, since there is no way to know how reflective the room surfaces are, and the scattered light has a huge impact. Assume, though, the countertops are 2 meters from the lamps and the reflectors on the lamps double the effective lumens. One LED lamp is 650 lumens, so 2*(650 lumens)/(2 meters)2 = 325 lux. (For comparison, your 60W lamps each produce 825 lumens, so you can do a simple ratio to estimate the effect.)

Q #2: when a LED bulb manufacturer states a certain light intensity for the bulb where is that intensity measured in relation to the face of the bulb? Is it measured 1 foot away from the surface? In the USA is that intensity measured in Lumens/ Sq. Ft., or is it Lumens / meter^2?

As was pointed out the 'brightness' is given in lumens, which is the total photopic output measured using a 'integrating sphere' to capture all of the light. A lumen, being a photopic parameter, is corrected for the response of the eye. A white sheet of paper will have the same luminance when exposed to the same number of lux, but its color (cool white / warm white) will depend on the color temperature of the lamp. A tinted surface may react differently, though, depending on the spectrum of the lamp.

Q #3: what percentage of the illumination diameter (@ the surface) is generally required in the overlapping areas?

You need to look at the effective illumination cone from the lamps, but remember that a matte white finished ceiling and walls will help to scatter and diffuse the light. What you want is the diffuse glow similar to a bright overcast sky, where there are no shadows. You might consider aiming some lamps at surfaces that will scatter the light, rather than using direct 'task' lighting. Maybe look at some under-cabinet lighting, too.

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#4

Re: Require Help/advice Regarding Led Lighting Choice Solution

06/16/2011 8:57 AM

I greatly appreciate all the very valuable information that you guys have provided to me. I am now able to calculate the approximate light levels on the granite tile countertops, which have a glossy surface. I think that this condition will help our situation.

With the chosen PAR30 lamp & light head, I have calculated the following:

H max. = 9.167' - 0.667' - 3.0' = 5.5' [1.676 m]

Hence min. I = 2 * (650 Lumen / (1.676m ^2)) = 462.8 lux

&

H min. = 7.167' - .667' - 3.0' = 3.5' [1.067 m]

Hence max. I = 2 * (650 Lumen / (1.067m ^2)) = 1,141.9 lux

I think that I can can live with those light intensity levels, especially since we have "ceiling white" painted ceilings and glossy surface countertops. The only detractor will be the satin finish of the oak cabinets.

I have drawn my kitchen layout (incl. countertops, sinks and stove) on IntelliCAD and found that if I have an approximate 50% overlap, based on the lamp spacings, that the light cone pattern occurring on the countertops nearly eliminates shadowing effects throughout the kitchen....provides a very good coverage! It appears that I can get away with installing a minimum of 6 of the chosen LED lamps, which aren't cheap by any stretch of the imagination! The big plus will be greatly reduced electrical bills (even with Solar PV system on the roof) over the long lifetime of the LED lamps, and not having to replace light bulbs every few months.

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Anonymous Poster #1
#5
In reply to #4

Re: Require Help/advice Regarding Led Lighting Choice Solution

06/16/2011 9:54 AM

Instead have you thought of putting a spotlight PAR on the countertop and ambient lighting around (where really the cross-shadows won't matter?)

This was explained in one of the links I provided. It will also save quite a bit on the lamps and power. You really don't need the 500Lux on the floor.

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#6

Re: Require Help/advice Regarding Led Lighting Choice Solution

06/16/2011 10:11 AM

Hi Anon, yes I have thought about installing the T-type (?) LED lamps (like fluorescent bulbs) under the upper kitchen cabinets in addition to the suspended lamps...it'll provide us with a solid wall of illumination.

Also, yes, I do understand that 500 lux in the floor surface is unwarranted, and not even necessary. The sample calcs that provided above in an earlier post were for the countertops only.....acceptable for me so far until we actually install the new LED lamps and track...then we'll tweak the lamp spacings and down angles to achieve the desired effects. With only 6 of the PAR30 650 Lumen LED bulbs I will be drawing 48W (8W apiece).

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