Air Conditioning Calculations

I seem to recall this being discussed a couple times previously, search the forums.

In one of the threads, the formulas were given as well.

Enjoy!

The factors to be taken into consideration for calculating the air conditioning unit are

1. Air flow of the fan ( in CFM)

2 . Input Power of the Fan

3 . Running Current of the Fan

4 .Rows of the Coil

5 Fin Per Inch of the coil.

Also take in to consideration the heat load from sources in the room, including lighting, insulation type and thickness of the walls, window size and heat loss through them and the maximum temperature during the hottest part of the year/environment that the control room is located in and the size of the room.

You need to determine the load consisting of:

• equipment
• lighting
• people
• envelope
• ventilation
• infiltration

You need to determine the type of HVAC equipment: 100% outdoor air, mixed air, a combination of the two? Variable air volume, single zone variable temperature, constant air volume with reheat etc.

As a rough estimate 400 cfm of unit capacity is needed for each ton of cooling (12,000 btuh). For outside air make-up a ton of capacity can handle about 160 cfm.

I know a guy that takes the square footage of the room and divides by 600. and that gave him the tons needed to cool the room. I didn't believe him, so I did a calculation that took me 6 hours and came up with the same answer... go figure

A simple thumb rules for you

when you want find the capacity of the machine you need

1. room area sqft/250 = ----tons

2.no of people nos/20 = ----tons

3.equip. load kw/3.57 = -----tons

4.Total all the answers you get. the minimum capacity of your machine is ready now

check it out with exisiting facility if you have

remember the all the loads through conduction is accounted in sl No 1.

assumption is the room height is 3 meters approx.

if it is more than that No: ans(1) X 1.2 upto 6 mtrs

beyond 6 mtrs ans X 1.7

My dear, remember these thumb rules holds good for

normal AC of 24 deg C and 65% RH and fairly good for an estimate

How ever you need to go to an HVAC engineer if your load works out beyond

at least 60 tons

or a specific application of controling temp or humidity and together temp and humidity, more fresh air application etc.,

Every one have scissor and can cut their hairs but it will not be in "perfect shape"

find your limits and use the above technic and enyoy it.