Re: [datacenter] HVAC

[Michael Lucking <michael@lucking.com>]

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On Tuesday 05 April 2005 09:27 am, Jon Swanson wrote:
> Could someone help me, it is finally spring and my brain is already
> wandering.
>
> I need to size an HVAC unit for a suite I have.  If I know BTU output of
> my equipment, how do I convert to AC unit Tonnage?

Not only equipment! You need to factor in everything. Here is a little cheat 
sheet....

All temps are in degrees F.

1) Windows exposed to the sun:
Use only one exposrue: Select the one that gives the largest result if no 
venetian or shading device is available mult X 1.4

1.1) South ____ sq. ft x (Max outside temp - 30) = _____ BTU/HR
1.2) E/W/SE ____ sq. ft x (Max outside temp - 3) = _____ BTU/HR
1.3) NW ____ sq. ft x (Max outside temp - 23) = _____ BTU/HR
1.4) NE ____ sq. ft x (Max outside temp - 25) = _____ BTU/HR
1.5) N ____ sq. ft x (Max outside temp - 85) = _____ BTU/HR

 
Answer for #1 MAX (1.1 - 1.5)

 2) All Windows not included in Item 1 (interior windows etc)

___ sq. ft x (Max exposure temp - 69) = _____ BTU/HR

 3) Walls exposed to sun

(Use only the wall with the eposure used in item 1)

 3.1) Light Construction ____ Lin. ft x (Max outside temp - 25) = _____ BTU/HR
3.2) Heavy Construction ____ Lin. ft x (Max outside temp - 55) = _____ BTU/HR

Heavy defined at 12" masonry or insulation.

 4) Shade Walls not included in Item 3

____ Lin. ft x (Max outside temp - 55) = _____ BTU/HR

 5) Partitions

(Interior Wall adjacent to an unconditioned space)

____ Lin Ft x (Max temp - 50) = _____ BTU/HR

 6) Ceiling or roof
6.1) Ceiling with Unconditioned occupied space above 
        ___ Lin Ft x (Max temp - 90) = _____ BTU/HR

6.2) Ceiling with Attic Space above
6.2.1) No Insulation ___ Sq Ft x (max temp - 83) = _____ BTU/HR
6.2.2) 2" or more ___ Sq Ft x (max temp - 90) = _____ BTU/HR
6.3) Flat roof with no ceiling below
6.3.1) No Insulation ___ Sq Ft x (max temp - 85) = _____ BTU/HR
6.3.2) 2" or more ___ Sq Ft x (max temp - 90) = _____ BTU/HR

 

7) Floor

(over unconditioned space or venter crawl space. ignore any heat gain from 
floor directly on ground or over unheated basement)
____ sq. ft x (Max temp - 90) = _____ BTU/HR

8) People (includes allowance for ventilation)
____ x 750 = _____ BTU/HR

9) Lights (if total wattage is know use 9.1 else 9.2)
9.1) ____ Watts x 4.25
9.2) ____ (sq ft floor space x 3 )Watts x 4.25

10) Computer load (some computers/routers acctually supply BTU/HR ratings else 
you will have to calculate it)

10.1) Total BTU/HR for all machines
10.2) Total max wattage x 3.4 = _______ BTU/HR

12000 BTU/hour = 1 Ton

______________________

Sum all the BTU/HR, this is your total load factor.

 
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