1. Regular Guest
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Jan 2003
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252

Venting small room question

Wondering what the formula/calculation is for determining this.

Small interior room = 10' x 10' x 8' high.

Owner has small server, phone data and a few other items within room. Total BTUH is 12,000 given off within room.

Owner wants to install a ceiling exhaust fan in room, transfer surrounding office area (large office) through door grille (figure 70* ambient air temp year round) into room at a given rate to keep room temperature at or as close to the surrounding space temp (70*). The exhaust air from the room will be dumped back into the office space creating a viscious circle of air. There is plenty of AC capacity to make up for the transfer of 12,000 btu to the office area.

What formula/calculation is needed to figure out what the minimum CFM is required to accomplish this? I know we could put in a large fan and or base on air changes per hour, but wondered if there was a more accurate way of determining the CFM.

Thanks

2. Professional Member
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Jun 2006
Location
Charlotte, NC area
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For sensible cooling (which is what you have with computer equipment)

CFM = BTU / [(T1 – T2) x 1.08]

So for your case with a 12,000BTU load with 70deg entering air and say a 75deg temp in the equipment room the results would be:

CFM= 12,000/(75-70)x1.08 = 2,222 CFM

To maintain 80 deg in the room would require 1,111 CFM

3. Professional Member*
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Feb 2010
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Cal
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How will the equipment like the dust associated with large volumes of air changes?

4. Professional Member
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Sep 2008
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Cedar Rapids, IA
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Originally Posted by riverman
Owner wants to install a ceiling exhaust fan in room, transfer surrounding office area (large office) through door grille
Whether a transfer grill is permitted in the door depends on the type of occupancy, ie what is the bldg/office primary use, and also what the regulatory agency is. If its healthcare, or any other government funded (even indirectly) activity then its not permitted.

Speak to the local fire marshall about this before you get involved. Its not a good idea in terms of liability in any case. Electrical equipment rooms can be sources of fire and smoke. The corridor outside the room is considered an egress path. Rooms like these have doors in order to protect the corridor for a short time from the smoke and fire and allow people time to escape.

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