What is the heat gain (in Watts) produced by an overhead screen projector in a typical school classroom?

Question

I am calculating the internal heat gains for appliances used in a school classroom. I can't find information on the heat produced by projectors.

Answer 1

First, look at the wattage of the lamp. This should be in the manufacurers specs. Then add 50% of that to account for the fan, interface etc.

Rule of thumb.

Answer 2

Virtually all of the electrical power going into the projector is going to end up as heat in the room. If you can look at a projector, the required power should be marked on it someplace. Looking at the units currently offered for sale, a 360 watt 82 volt bulb seems to be common. There is probably some kind of regulator that reduces the voltage and perhaps rectifies it from 120 volts AC. That is probably no more than 90% efficient and adds 10%. The fan probably adds another 5 or 10%. I think 430 watts would be a reasonable estimate.

Answer 3

The bulbs are anywere between 85W and 150W (I've replaced a few projector bulbs in my day).

Let's assume your projector is a 100W bulb. Incandescant bulbs are very inefficient at converting electrical energy to light, so most of that 100 W is going into heat -- about 95 Watts of heat (5% light power).

As for the fan, I consider that incidental. The fan is probably rated for 15-20 Watts, which adds another 5 Watts of heat.

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