cooling an elevator cab

[chicagoelevatorman]

I need help with cooling an elevator cab. I have 30 elevators with 1400 watts of halogen cab lighting generating a lot of heat. can this be dissipated through ventilation, if so how much cfm of air movement do I need. Or will I need some type of air conditioning unit. any calculation would be apreciated. The cab dim. are 5'x6' with 9 ' ceilings

 

[MintJulep]

Is that 1,400 watts per cab?

 

[chicagoelevatorman]

Yes thats 1400 watts per cab !

 

[IRstuff]

Are they doing surgery in those cars?

My condo's elevators probably have less than 120 W of incandescent lighting.

TTFN

 

[chicagoelevatorman]

no, but they double as the health club saunas

 

[MintJulep]

First thing I would do is issue sunscreen to everyone in the building.

Next I would install occupancy sensors in each cab to turn the lights off when empty to reduce the heat load.

It's possible with ventilation only, but it depends on the temperature of the air available for ventilation (typically from the elevator shaft).

Short-form equation is:

q = 1.07 x cfm x (Ti - To)

where:

q = heat load in BTH/hr (1,400 watts ~= 4800 BTU/hr)
cfm is the cubic feet of air at temperature To that you need.
Ti is the temperature in the cab you want to maintain.
To is the temperature of the air you have available for ventilation.

 

[chicagoelevatorman]

Thanks for your reply. If I understand your formula. to maintain a max temperature rise of 2 degrees above ambient shaft air I wolud need 2250 cfm of air movement

1.07 x 2250 = 2407 x 2 = 4815 btu/h

we do have timers to shut off the lights after 1 minute of no demand. the fans stay running, although they probably do not move the amount of air necessary

 

[IRstuff]

That translates to about 25 mph in a 1 ft sq area.

TTFN

 

[MintJulep]

2250 cfm is a lot of air for a 5x6x9 area. Better than 8 air changes per minute.

Likely not comfortable. You're gonna need colder air.

Why is there so much lighting power in these elevators?

 

[chicagoelevatorman]

the architect designed the lighting for a specific look without considering heat. I needed this info to convince the building managment that ventilation is not the anwser that the lighting scheme will have to change. any more amunition would help and be apreciated.

 

[IRstuff]

You could, of course, duct the fans only at the lights and then exhaust the waste heat out the top into the shaft.

Another issue that crops up here is that airflow provided for the lights will cause faster cooling of the lights when they are turned off. The high thermal gradient may cause premature failure of the filaments, since the vaporized metal cycle will shut off prematurely because the cooler than usual glass will cause condensation of the metal onto the glass, rather than back on the filament.

TTFN

 

[GMcD]

Or, ask why someone wants to create an "easy bake oven" in an elevator cab, and eliminate the source of the problem. Get rid of the lights and replace them with equivalent low heat producing compact flourescents. To use an energy waster system like that in this day and age is irresponsible.