Why AC rated
in Tons, Not in kW?
AC
(Air-conditions and Refrigeration are always rated in Tons.
Air
conditioners are always rated in Tons capacityinstead of kW because Air
conditioners are designed on the basis of quantity of heat removal from room,
hall or specific area. Quantity of heat is termed in Tons means if an air
conditioner is able to remove 1000 kilocalories of heat or 4120 kilojoules or
12000 BTU of heat in an hour that AC rated as 1 Ton of AC because 1000
Kilocalories or 4120 kilojoules or 12000 BTU equal to one Ton of heat. Also,
this is the same case for freezer and refrigerator i.e. refrigeration system.
Good to
know:
BTU =
British thermal unit. A measurement of heat, specifically, the amount of heat
needed to raise the temperature of a pound of water by 1°F.
Definition
of Ton
A Ton of
refrigeration (RT) is approximately equivalent to 12,000 BTU/h or 3,516.8528 W
or 4.7142Hp.
A Ton of
refrigeration (RT) is a unit of power used to describe the heat-extraction
capacity of air conditioning and refrigeration equipments. It is defined as the
heat of fusion absorbed by melting 1 short ton of pure ice at 0 °C (32 °F) in
24 hours.
How many kW
and HP are there in 1 Ton?
1 Ton =
3.5168525 kW = 4.714Hp
Explanation
1 Ton =
12,000 BTU/h
1 Watt =
3.412141633 BTU/h
1 Ton =
12,000 / 3.412141633 = 3,516.8528 Watts = 3.5168528 kW.
1 Ton =
3,516.8528 Watts = 3.516 kW.
Also
1 Ton =
3,516.8528W / 746 = 4.7142798928 Hp →→→ (1 Hp = 746 Watts)
1 Ton =
4.714 Hp
How to
convert Ton to Kw and vice versa?
One
RT(Refrigeration Ton) = 3.5168528 kW…
1 RT =
3.5168528 kW
1 kW =
0.284345 RT(Refrigeration Ton)
1 kW =
0.28434517 RT
So,
The power P
in kW = Power P in RT (Refrigeration Ton) times 3.5168528….
P(kW) =
P(RT) × 3.5168528
Example
Convert 3
Ton AC into kW i.e. Convert 3 RT to kW.
Solution:
P(kW) = 3 RT
× 3.5168528
P(kW) =
10.55 kW
3 Ton AC =
10.55 kW
How much
Current in Ampere will a 2 Tons AC draw in Single Phase & Three Phase
System?
Suppose,
There are 230V and Power factor = Cosθ = 0.95 in Single Phase AC system…
1 Ton =
3,516.8528 Watts = 3.516 kW.
2 Ton = 2 x
3.516 kW = 7.032kW = 7032W
Power in a
Single Phase AC System
P = VxI Cosθ
and current…
I = P / (V x
Cosθ)….. Where Cosθ = Power factor
I = 7032W /
(230V x .95)
I = 32.18 A
Therefore, a
2 Ton AC (Air-condition in Single Phase AC system will take 31.18 Ampere
Current
And in Three
Phase System
Suppose,
There are 440V and Power factor = Cosθ = 0.85 in Three Phase AC system…
Power in a
Three Phase AC System
P =√3 x
VLxIL Cosθ and current….
I = P /(
√3xVxCosθ)
I = 7032W /
(1.732 x 440V x .85) Where Cosθ = Power factor and √3 = 1.732
I = 10.855 A
Therefore, a
2 Ton AC (Air-condition in Three Phase AC system will take 10.855 Ampere
Current
Good to
Know:This is just calculation based on Electrical formulas. In real, Air
conditioner current depends a lot on operating conditions such as ambient
temperature, refrigerant pressure, Energy Efficiency Ratio (EER) etc. for
instance, if EER is 6, then input power for 2 Tons Air conditioner is 24000BTU/
6 = 4000 watts..
If this is a
230 volt system, then air conditioner load current would be = 4000/(230x.95) =
18.5 A
For More
detail…Check the Air conditioner Name plate rating.
Another
similar rating is Coefficient of power (COP) which is the output power in watts
divided by input power, so with a COP = 1.8, for instance, input power for 2
Tons Air conditioner is 7032W / 1.8 =
3906 watts. Now you can find current by using the above method which is equal
to 18A approx.
How many 2
Ton A.C (Air conditioner) can I run on a 25 kVA Generator?
2 Ton = 2 x
3.516 kW = 7.032kW = 7032W
The
Efficiency of Utility Power Generator is 90% approximately.
Efficiency
of Generator = 25kVA x (90/100) = 22.5kVA
Now the
Number of 2 Ton AC (Air conditioners) which you can run on a 25 kVA Generator
smoothly..
22.5kVA /
7032W
= 3
So you can
run Three Air conditioners of 2 Tons each on a 25kVA Generator.
What is the
suitable rating of MCB for 2 Ton and 1 Ton AC (Air conditioner) and why?
As we have
calculated the load current for 2 Ton AC Air conditioner…
Calculated
Current for 2 Ton A.C = I = 32.18 A
Now 40A
Class “C” MCB (miniature circuit breaker) would be suitable for 2 Ton AC
(air-condition) because in starting time it takes more current of the full load
current
And 20 A
Class “C” MCB would be better for 1 Ton AC (air-condition)
Good to
Know:
Class “’C’
Type MCBs
Class “C”
Type MCBs are suitable for installations with high inrush of current at the
starting switching time. in other words, equipment and devices having inductive
loads such as air-conditioners, induction motors, fluorescent lamps,
transformers etc.
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