Heat Load Calculation for Lighting System

What happens when the assumption is made that all of it is converted to heat?

Does it mean that all of the light energy will also be converted to heat?

Yes. So?

40W and 28W.

Any thoughts on using higher efficacy lighting so as to reduce the heat load on the air conditioning system?

the most bang for your buck in lighting would bebetween metal halide with 70 to 115 lumens per watt, and high pressure sodium lights with 50 to 140 lumens per watt. See link http://www.mge.com/home/appliances/lighting/comparison/htm

another way to reduce the lighting load is do spot lighting just on the areas you need light. Also motion sensors to turn lights off when no one is in the area. for that you would want to use flourescent or an instant on light.

jonathan555

Invitation declined.

Take the total wattage of all your lamps and take it times 3.414. That value it how many btu's there are per electrical watt.

Jonathan555

The old toolbox...

http://www.engineeringtoolbox.com/heat-gain-lights-d_709.html

P = (1,000 lumen/m²) / (0.5 (60 lumen/W))

= 33.3 W/m^{2 = 114 btuh}

These documents may help you the way you want to calculate the lighting heat gain:

http://www.pdhonline.org/courses/m196/m196content.pdf (page 34-35)

https://www.cedengineering.com/upload/Cooling%20Load%20Calculations%20and%20Principles.pdf ((see section 9.2.2, page 26)

Lighting heat gain also can be counted based on thumb rule of square feet (or square meter) considering usage of the space.

- MS

Electric lights generate sensible heat equal to the amount of the electric power consumed. Most of the energy is liberated as heat, and the rest as light which also eventually becomes heat after multiple reflections. For heat gain Fluorescent = Total Watts X 1.25 for Incandescent+ Total watts.

Planning that all the lighting energy, when everything is switched on, is heat energy makes the calculation far simpler and errs slightly on the side of having more cooling than probably needed - it being always better to err in this manner.

Changing to more efficient lighting will help even more....

Good insulation and shaded windows if you live where it is really hot in the summer, will also be a great idea.....many forget good insulation.

We had our house fully insulated (it was not bad before) which means that in a hot summer, some people (visitors) ask us if we have a running AC when they enter the house.... We do have a portable system, but that has not been used since 2008 because of the insulation.....

In winter, I can easily go through the day with no heating on.....even with -10°C outside.....the house is a real comfort zone, summer and winter.

Insulation, insulation, insulation, insulation, insulation, insulation, insulation, insulation, insulation, insulation, insulation and more insulation.

For conventional bulb system convert 95 percent power for heat. For tube light convert 65% of Watt energy for heat. use volume of human using the room when it more than 25 percent of total volume of the room. This includes typical furniture in the room. You will have total heat generated and then assume 70oC is comfort level and you will know what power load you need for air conditioner. Add in that 25% and that is your design rules.

If you use LED then put 10% for heat instead of 95 and 65 percents and human heat stays same

BTU /Hour gain= 3.4 X watts

For heat generated by lights incorporating ballasts,heat loss in ballast should be taken into account. Also consider the colour temperature of the light.

Thank you all for the valuable comments posted in this discussion forum.