IT is  a latent heat absorb from particular area in a 
closed room

its means that any AC machine CAN remove 720000 k/cal heat 
to a particulaer area that capacity can be said as 1 ton.

Plaese ignore my first answer 
its means that any AC machine CAN remove 3000K.CAL /HR heat 
to a particulaer area that capacity can be said as 1 ton.

In simple 1 tonne refregeration effect of AC is equal to 
same amount of cooling which have been achieved by 1 Tonne 
of ice block in 1 hour. i.e 3000K.CAL /HR

1 Tommage Rating(1TR)=12000KCal/Hr

The cooling produced by melting of 1 ton of ice in a day is 
taken as unit of refrigeration (in tons). Now unit of 
refrigeration used in S.I. System is KW.
 1 ton of refrigeration 
= mass of ice x latent heat of ice / 24 hrs 
   
= 900 kg x 335 KJ/Kg         ( one short ton = 900 kgs )
  ------------------
    24  x 3600 secs
= 3.4895 KJ/Sec
say 3.5 KJ / Sec = 3.5 KW

that is 1 ton of refrigeration = 3.5 KW

Please ignore my answer #5
1KW= 860 KCal/hr
1 KCal/hr = 3.96 BTU
1 TR(tonnage rating)= 12000 BTU
 Answers 4 & 6 are the closest defination as given above
therefore it follows
3.5 KW = 3000 KCal/hr = 1 TR

One ton of refrigeration is the amount of cooling obtained 
by one ton of ice melting in one day: 3024 kCal/h, 12,000 
Btu/h or 3.516 thermal kW

It is the Heat required to melt one ton of ice (2000 lbs) 
in 24 hours without increase in its temperature

= 1 x 2000 lbs x 144 btu / pound = 288000 BU or
1200 BTU/hour or 200 BTU / minute

The amount of the heat required to convert 1 ton (2000 
pounds)of ice in to water within 24 hours. The initial 
temperature of water is 0 deg C.

Latent heat of ice= 144 BTU

1 TR= 144 X 2000
    = 288000 BTU/24 

For 1 hour

We can divid by 24 So  288000/24=12000BTU



1TR=12000BTU/Hr
   =3024 K Cal/Hr
   = 12600 K Jul/Hr
   = 3.52 HW OR K Jul/Sec