air conditioning question

Your question has so many parts I don't know where to start. First you can't measure the surface area of a the coil to determine the tonnage. The tonnage is determined as much by the size of the compressor as the size of the coil. Your best bet is to look at the name plate, the tonnage is there altho in code, but it is there.

If your asking about what tonnage you need for a given size room or building, then you need to do a load calculation, many are available on the web. just goggle it.

someone had told me about the calculation of tonnage of AHU through GPM and delta T, but i want to make sure of it,plz reply

The formula Q [Btu/hr] = 500 x GPM x ΔT is for chilled water through chillers or coils.

Where 1 Ton = 12000 Btu/hr

EXAMPLE:

Size chilled water flowrate for 40ton chiller

Q=500 x GPM x ΔT

(40 ton)(12,000 BTU/Hr)=500 x GPM x (54 - 44 Deg. F)

GPM = 96

Is that what you are looking for?

yes , im looking for this butcould u tell me if yhe air handling unit is kept in the open yard and if u want to calculate the tonnage of it,how we can do that,coz the tonnage is not mentioned on the name plate only the kw or the model num and moror capacity, plz let me know

plz tell me the formula for calculation of CFM and LTS (litres per sec)airflow from FCU or AHU