lux v lumen

[Farmelectrics]

if emergency lighting has only to be 1 lux how many lux in a lumen ha ha head scrastching can anyone explain in simple terms

 

[Pete999]

Google lumens/Lux easy

 

[D Skelton]

First of all the recommendation is that emergency lighting provides an illuminance of 10lux at floor level with a minimum of 2lux. I don't know where you've got 1lux from?

Secondly, they are different units, you can't say how many lux are in a lumen, it would be like asking how many kilograms are in a meter. A lumen is essentially the amount of visible light emmitted from a source, lux is the area over which luminous flux is spread (a flux of 200 lumens spead over an area of 10m[SUP]2[/SUP] = 20lux). Like 10 grams of butter can be spread over 15cm[SUP]2[/SUP] of toast.

There are tonnes of different calculations that can be used when designing lighting making use of units such as lumens, lux, luminous flux, luminous efficacy, luminance, candella, coefficient of utilisation, steradians etc... So what is it exactly that you want to know? I am by no means an expert but I will do my best to help

 

[ipf]

Doing a church, how many candelas in a candelabra ?

 

[Farmelectrics]

First of all thanks for info d Skelton bit wiser with that someone on here last night told me 1 lux there's a building that we look after were a mock shop was built when doing are emergency light test we foun there were no emergency lighting in the area other than the running men above door highlighted the issue but was then asked what level of light was required and if truthfull didn't have the answer hence me picking your brains

 

[Farmelectrics]

The area is roughly 60 square metre

 

[D Skelton]

All areas 60m[SUP]2[/SUP] or larger must be lit in the event of the faliure of normal lighting.

To work out how to do this you must first find out what the luminous efficacy of the light fittings you propose to use is. An 8 watt fitting should have an efficacy of around 10lm/w (lumens per watt).

With that in mind you then need to work out what level of lux you require at ground level. This should be 10lux for emergency lighting but 2 lux is acceptable.

The calculation is as follows:

(2lux x 60m[SUP]2[/SUP]) / (80lumens x 0.7) = the number of fittings required in this situation to give an illuminance of 10lux at floor level with light fittings evenly spaced. In this case the number of fittings required is 130.

A couple of things to take into account:

1. This is only a rough guide assuming a ceiling height of between 2-3m
2. 0.7 is a standard value used when the lamp's maintenance factor and the light's coefficient of utilisation are not known. Essentially, over time, it is expected that only 70% of the light that the fitting should be emmitting will actually be hitting the surface it is supposed to be hitting.

 

[Farmelectrics]

So why when we have small offices is there a need for emergencys when they are no were near 60metre square

 

[D Skelton]

In smaller areas it is only escape pathways that need to be illuminated in the event of a faliure of normal lighting. For example the center run of an office from the entrance doors to the fire exit at the opposite end.

A clear lit pathway to the route of escape is what you need, whether that be a room or a hallway.

 

[tazz]

I gave farmelectrics the information on minimum of 1 lux measurement in escape routes and 10 lux measurement in high risk areas.
this is the minimum to be measured, within the designed area, commonly 10m2

 

[D Skelton]

I've just got my 5266 out and it does say minimum of 1 lux in large, free and open areas where people have freedom of movement, but not less than 2 lux in stairwells and exit pathways. If there is no freedom of movement (I'm assuming there isn't as it's an office) then it's 2 lux.

Happy to eat humble pie if I'm wrong though tazz

 

[tazz]

No Skelton your correct, 1 lux measured in all areas covered. 10lux in Risk areas, which could be chemical labs, storage areas. Offices unless the form part of the escape route area not required to have em lighting. Public areas as you stated 1 lux........TBH any modern lighting these days will exceed these levels.
I think some of the miss leading things to people here is the measurement of lux over the cover area

 

[ian.settle1]

Doing a church, how many candelas in a candelabra ?

Del Boy should be able to give you the answer to that