Sensible Heat Load Question

[briman]

I am trying to determine the heat load in a clean room. The room has a t-bar ceiling with recessed flourescent lights. Does anyone know how much heat they will contribute to the room since they are recessed. I assume it is some percentage of power wattage of each unit. Alow was wondering how much heat is produced by the self powered hepa units which will be flush mounted in the ceiling. Possibly some percentage of the horse power or wattage requirement.

 

[chicopee]

For heat input to the room, I would use the total bulb wattage per fixture.

 

[abeltio]

see ASHRAE standards... they have the best data for these type of calculations.

saludos.
a.

 

[tombmech]

abeltio is correct - ASHRAE is the best source for this data. As a general rule-of-thumb, about 75% of the heat from recessed fixtures is rejected to the space above the ceiling. However, you have to factor in the fixture efficiency to determine that heat.

Most important, you don't get this rejected heat for "free." It may not factor into the supplied cooling for the specific room, but it will show up as a coil load at the Air Handler.

Finally, if the space above the ceiling is not a return air plenum, then it does factor into the specific room load.

 

[HVAC68]

Regardless of where the heat is dissipated - i.e. into the air-conditioned space or the return air space above the ceiling (I have made this assumption that the space above is the return air space), the total load remains same. However, the heat that is dissipated into the return air space does not form part of the room load (it forms part of the total coil load, though) and consequently the rooom sensible would be relatively lesser, which in turn would mean lesser dehumidified air quantity requirement.

HVAC68