Conversion Of Foot Candles To Watts

[north star]

& & & &

From the 2006 IBC, Section 1006.2:
"The means of egress illumination level shall be not less than 1 foot candle
( 11 lux ) at the walking surface."

Can someone please provide a calculation or conversion of "foot candles [ "lux" ]
to watts.....I know that the installation height of the lighting fixture will
have a determination of the amount of watts required to be able to provide
a compliant installation of illumination at the foot level.

How do you determine a compliant location of the combo "Exit & Emergency
Light Packs"?

Thanks for any input!

& & & &

 

[Dennis Alwon]

You may need to see the photometrics of the fixture.

 

[billsnuff]

what dennis said...........and heres a formula: Number of foot-candles x 10.76 (lux.) x 0.001496 to convert foot-candles into watts.

 

[Electric-Light]

You can't convert between the two, just like you can't convert between psi and pounds. They might say "30 lbs of air", but they really mean psi and it doesn't actually make your car heavier by 30 lbs.

 

[charlie b]

Number of foot-candles x 10.76 (lux.) x 0.001496 to convert foot-candles into watts.

What assumptions go into this formula (e.g., characteristics of the luminaire and height above ground)? This is not a simple unit conversion problem.

 

[barclayd]

what dennis said...........and heres a formula: Number of foot-candles x 10.76 (lux.) x 0.001496 to convert foot-candles into watts.

There is no direct conversion factor. It all depends on the lamp type, wattage, luminaire type, mounting height, etc. The energy codes generally limit the watts/sqft, but you have to calculate the footcandles based on the lamp/luminaire configuration. Then the watts are apparent.
db

 

[billsnuff]

What assumptions go into this formula

should have had watts as W/m(sqd) and I don't remember for sure what wavelength. just some old class notes. So I guess I stick with the first half of my answer.

what dennis said

 

[480sparky]

I don't see how footcandles can be converted to watts.... they're measuring different things. If you could, then how bright will a 1500w hair dryer be?

 

[Besoeker]

I don't see how footcandles can be converted to watts.... they're measuring different things. If you could, then how bright will a 1500w hair dryer be?

Nicely put.
Made me smile.

 

[K8MHZ]

I don't see how footcandles can be converted to watts.... they're measuring different things. If you could, then how bright will a 1500w hair dryer be?

How many volts is a 150kW steam engine?

:roll:

 

[billsnuff]

1 foot-candle = 10.763910417 lux

1 lux = 0.000000146 watt/centimeter^2 (at 555 nm)

guess these aren't true or they mix like oil and water??

 

[spikes2020]

& & & &

From the 2006 IBC, Section 1006.2:
"The means of egress illumination level shall be not less than 1 foot candle
( 11 lux ) at the walking surface."

Can someone please provide a calculation or conversion of "foot candles [ "lux" ]
to watts.....I know that the installation height of the lighting fixture will
have a determination of the amount of watts required to be able to provide
a compliant installation of illumination at the foot level.

How do you determine a compliant location of the combo "Exit & Emergency
Light Packs"?

Thanks for any input!

& & & &

I also do lighting designs for tunnels and all kinds of stuff, for $100 you can get http://www.visuallightingsoftware.com/eStore/products.asp and it will tell you the foot candles of your location. It comes with many different types of lamps with different lenses you will need. Make sure you have the correct "*.ies" file. the IES file is a pattern that shows how the lamp and lens distributes the light. A spot light and flood lights will be completely different with the same wattage's. Also you can download many of the IES files from the manufacture's web stie like Lithonia's http://www.lithonia.com/

Key things to note;

Reflectance off of walls can add a lot of light to a room so that could be something to keep in mind.

The ballast and lamp will reduce in output over time so in 6 months the bulb will be putting out less light than first installed, and the ballast in 2 to 5 years will do the same. All of these factors need to be calculated to get the required foot/candles needed. Oh and don't forget dust and how often you clean them. (not as important unless you work underground)

There are some good generic numbers you can run if you are doing a normal office building but for my line of work each tunnel is different.

hope that helped =)

 

[Besoeker]

How many volts is a 150kW steam engine?

:roll:

Watt's you're question?

 

[Electric-Light]

1 foot-candle = 10.763910417 lux

1 lux = 0.000000146 watt/centimeter^2 (at 555 nm)

guess these aren't true or they mix like oil and water??

lux means 1 lumen per one square meter, or its known as "photometric intensity".

lumen is a unit of quantity of perceived light weighed to photopic sensitivity of our eyes and its known as "photometric quantity".

1W/m^2 of 555nm(green) will have a higher lux than 1W/m^2 at 700nm(deep red). This measure is referred to as "radiometric measure".

A 15W CFL that puts out 750 lumen and total optical energy of 3W has an efficacy of 50lm/W and an efficiency of 20%.

 

[north star]

* * * *
Please forgive a lowly Bldg. Inspector, but I am still unclear as to whether or
not a typical combo "Exit & Emergency Light" fixture is providing the minimum
foot candle lighting at floor level.

The scenario: You are reviewing a set of Commercial plans and note that
additional emergency lighting is required by the building code [ the Means
Of Egress illumination ].....The RDP simply adds a graphic onto the REVISED
set of plans, ...in the areas required to have MOE lighting.

The code question is: Do the typical Exit & Emergency Light Combo fixtures
provide adequate lighting at foot level, to be able to safely navigate out of
the building ?

2nd question: What size of wall mounted E & EL fixture bulb is need to
provide 1 footcandle at ground level? Let's say the typical mounting
height is 9 ft. above the finished floor surfaces.

Thanks for any input!

My contention is that the typical E & EL fixtures does not provide
adequate lighting [ at feet level ] to be able to navigate out of a
building when the normal power supply is interrupted.
We are assuming that there is no fire and that there is no smoke
filling the bldg. areas.

What say ye?

* * * *

 

[Smart $]

* * * *
Please forgive a lowly Bldg. Inspector, but I am still unclear as to whether or
not a typical combo "Exit & Emergency Light" fixture is providing the minimum
foot candle lighting at floor level.

The scenario: You are reviewing a set of Commercial plans and note that
additional emergency lighting is required by the building code [ the Means
Of Egress illumination ].....The RDP simply adds a graphic onto the REVISED
set of plans, ...in the areas required to have MOE lighting.

The code question is: Do the typical Exit & Emergency Light Combo fixtures
provide adequate lighting at foot level, to be able to safely navigate out of
the building ?

2nd question: What size of wall mounted E & EL fixture bulb is need to
provide 1 footcandle at ground level? Let's say the typical mounting
height is 9 ft. above the finished floor surfaces.

Thanks for any input!

My contention is that the typical E & EL fixtures does not provide
adequate lighting [ at feet level ] to be able to navigate out of a
building when the normal power supply is interrupted.
We are assuming that there is no fire and that there is no smoke
filling the bldg. areas.

What say ye?

* * * *

There is no easy answer to your questions. There is no direct correlation betweeen the lamp wattage and or lumen data to the foot candles provided at foot level... even knowing the location and directivity of the luminaire.

It would be the designer's responsibility to reasonably predict the requirement is met. From an inspector's viewpoint, the easiest verification is to just use a light meter on final (or part thereof, since the best time to measure is at night). Otherwise, you would have to totally rely on photometric software plus accurate luminaire and lamp data entry and the accuracy of the software's results. Of course this could be done in old school fashion (i.e. on paper without the aid of software other than a calculator or spreadsheet)... but do really feel this would be appropriate for a plans review department?

 

[K8MHZ]

There is no easy answer to your questions. There is no direct correlation betweeen the lamp wattage and or lumen data to the foot candles provided at foot level... even knowing the location and directivity of the luminaire.

It would be the designer's responsibility to reasonably predict the requirement is met. From an inspector's viewpoint, the easiest verification is to just use a light meter on final (or part thereof, since the best time to measure is at night). Otherwise, you would have to totally rely on photometric software plus accurate luminaire and lamp data entry and the accuracy of the software's results. Of course this could be done in old school fashion (i.e. on paper without the aid of software other than a calculator or spreadsheet)... but do really feel this would be appropriate for a plans review department?

Not only that, different luminaries will produce different amounts of measurable light per watt. There are even differences in the same design, take a look at the range of lumens just from one incandescent manufacturer to another. I have found that the more light per watt, the shorter the life of the bulb.

Foot candles per watt may be a measurable amount in a fixed setting, but I don't see it as being a reliable stand alone conversion by any stretch of the imagination.

 

[steve66]

Look on Page 36 and on of the Emergency Section of the Lithonia Lighting Catalog:

http://www.acuitybrands.com/Libraries/PSG/Lithonia_Emergency_Systems.sflb.ashx

They give graphics of spacing needed for 1 FC, and they have tables that show mounting heights vs. spacing needed.

Of course, you might see other EM fixtures specified, but this should give you a good start.

I've reviewed designs where the emergency lighting was clearly not adequate.

Steve

 

[weressl]

I don't see how footcandles can be converted to watts.... they're measuring different things. If you could, then how bright will a 1500w hair dryer be?

A more apt analogy would have been: the same way as you convert electric power to mechanical shaft power on a motor. The 'conversion factor' is what is summarized in the 'efficiency' number.

In lighting terms it is called the 'efficacy' number, eg. lumens/watt. Furthermore the actual delivered illumination is reduced by the fixture's optical efficiency, distance, reflectiveness and 'dirt factor' - the allowance to decrease illumination level over time, between optics cleaning.

 

[north star]

* * * *
Much thanks to you all for your input!....The Lithonia Catalog is a big help!....The graphic
illustrations on Page 475 thru 480 REALLY help me understand this conundrum.

* * * *