Why do AC manufacturers rate 1 ton units as 1.5 horsepower when the math shows 4.7?

[riezer]

A manufacturer like Carrier or Panasonic listed their 1 Horsepower Aircon as having 9,500 KJ/h and 1.5 Horsepower Aircon as 13,000 KJ/h. But it doesn't tally with the BTU conversion.

1 ton refrigeration = 12000 Btu/Hour = 12,661 kJ/Hour = 3.517 kW

now 1 watt = 0.00134102209 horsepower therefore 3.517 kW = 4.7 Horsepower!

But the Carrier/Panasonic manufacturer listed 1.5 Horsepower Aircon has having 13,000 KJ/hour which is equivalent to 12000 Btu/Hour or 1 ton. Yet calculation of this data show 4.7 Horsepower. Why did Carrier/Panasonic, etc. listed them as 1.5 Horsepower Aircon?

I've been searching in net for this for hours but can't find the reason. Anyone got any idea why?

 

[russ_watters]

1.5 hp is the input mechanical work, not the cooling output.

 

[xxChrisxx]

http://en.wikipedia.org/wiki/Coefficient_of_performance

 

[riezer]

1.5 hp is the input mechanical work, not the cooling output.

You mean 3517 Watts (equivalent to 4.7 Hp) is the cooling output? Can you use watts as cooling output (the input being 1.5 hp as you mentioned)?

 

[russ_watters]

Yep. And power is power - you can use watts, horsepower, btu/hr, tons etc.

 

[riezer]

If the input is 1.5 HP (1200 watts) and the output is 4.7 HP (3517 watts). Doesn't it violate law of conservation of energy because the output is greater than the input?

 

[russ_watters]

No. The input electrical energy isn't the only energy input. Please read Chris's link...