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How many amps should a one ton AC consume

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danishdeshmuk

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How many amps should a one ton AC consume or usually a 1 ton ac draws how many amps ?

And how much time does a split ac usually take to reach its rated or maximum amperage ?

thanks
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

danishdeshmuk said:
How many amps should a one ton AC consume or usually a 1 ton ac draws how many amps ?
Click to expand...

This is only a rough conjecture...

Suppose a window A/C weighs 50 lbs and uses in the area of 10A at 120V...

Then a 1 ton A/C (2,000 lbs) would use about 40 times that amount of power.

And how much time does a split ac usually take to reach its rated or maximum amperage ?

thanks
Click to expand...

Motors often draw a surge current on starting up, at 2 or 3 times their rated amperage. Then the unit settles to normal draw as the motor comes up to speed.

Sometimes I have noticed lights dimming as I switched on an air conditioner. They generally dim for a fraction a second, which suggests that's how long the surge lasts.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

BradtheRad said:
This is only a rough conjecture...

Suppose a window A/C weighs 50 lbs and uses in the area of 10A at 120V...

Then a 1 ton A/C (2,000 lbs)...
Click to expand...

When used in the air conditioning industry, the term "ton" does not refer to weight. It refers to the ability to move 12000 BTU/hr.

In answer to the original question, when I was researching this to debug my own central AC I found a reference on the web that said for a 220- volt unit it is about 6.5 amps per ton. But my measurements are much lower than that. So I am not sure. The AC guy I had over to look at my system said that the current depends a lot on operating conditions - ambient temperature, refrigerant pressure, etc. And therefore you can't count on a constant current draw for a given size AC unit.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

danishdeshmuk said:
How many amps should a one ton AC consume or usually a 1 ton ac draws how many amps ?

And how much time does a split ac usually take to reach its rated or maximum amperage ?

thanks
Click to expand...

Before anyone can calculate the amps, we have to know the voltage powering the AC, right?

Ratch
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

My furnace has a variable speed DC motor that is also used for AC. When the motor goes fast then of course it draws more power.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

The fan motor in the furnace is a small part of the total AC current draw. The biggest power consumer is the compressor motor in the outside unit. That is the one that is rated in "tons", and that is probably the one the OP is asking about.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

Everyone can speculate all the want, but until we know the voltage, we cannot calculate the amps.

Ratch
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

I tried adjusting the pulley wheel diameter of the AC fan in my old furnace and got its current up to 15A. The new furnace has a DC fan motor with adjustable speed and it blows much more air than the old one at its highest speed. It probably draws a pretty high current.

The outside unit has a huge fan that spins fairly slowly. Does its motor also drive the compressor?
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

No, the compressor motor is in the compressor, just like in most refrigerators.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

danishdeshmuk said:
How many amps should a one ton AC consume or usually a 1 ton ac draws how many amps ?

And how much time does a split ac usually take to reach its rated or maximum amperage ?

thanks
Click to expand...

5 to 7 Amps if you live in India (230V / 50Hz). The exact ratings vary as per manufacturer.

--Sharik
 
Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

sharikbaig said:
5 to 7 Amps if you live in India (230V / 50Hz). The exact ratings vary as per manufacturer.

--Sharik
Click to expand...

Well, finally we get a voltage. Now we can get to work. So, the heat of fusion of ice is 143 BTU/lb. That means it will take 143 BTU to freeze 32°F water at into 32°F ice. A 1 ton AC will freeze a ton (2000 lbs) of 32°F water into 32°F ice in 24 hours. That means it will consume 286000 (143*2000) BTU's of energy in a 24 hour period. 286000 BTU converts into 301745973.85 joules. In 1 hour, 12572748.91 joules or 12572.748.91 kilojoules will be consumed. Therefore 230*I*3600=12572748.91 ====> I = 15.18 amps RMS.

Ratch
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

Therefore 230*I*3600=12572748.91 ====> I = 15.18 amps RMS.
Click to expand...
That's electrical input corresponding to the net "cooling power". For a brief reference to involved units, see https://en.wikipedia.org/wiki/Ton_of_refrigeration

But AC is a heat pump. The electrical input is considerably smaller than the pumped cooling power. On the other hand, the compressor refrigerator has limited efficiency, and less than unity power factor.

To answer the original question exactly, you need to know the refrigerator data as well as actual evaporator and condensor temperature. More easily, refer to a recent AC catalog.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

FvM said:
That's electrical input corresponding to the net "cooling power". For a brief reference to involved units, see https://en.wikipedia.org/wiki/Ton_of_refrigeration

But AC is a heat pump. The electrical input is considerably smaller than the pumped cooling power. On the other hand, the compressor refrigerator has limited efficiency, and less than unity power factor.

To answer the original question exactly, you need to know the refrigerator data as well as actual evaporator and condensor temperature. More easily, refer to a recent AC catalog.
Click to expand...

Yes, that is the current needed if the AC unit is 100% efficient. If not, it will take more electrical power. Since I don't know what unit to look up to find the coefficient of performance (COP), any catalog is worthless.

Ratch
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

But the thermodynamical COP is considerably above unity for the temperatures involved with an AC machine.

If we assume an evaporator temperatur of 5°C and a condensor temperature of 50°C, we get a

Carnot COP = TL/(TH-TL) = 278/(323-278) = 6.2

So even with a cheap compressor and other losses, the ratio of pumped heat to electrical input power will be in a range of 2.5 to 4.

https://en.wikipedia.org/wiki/Thermodynamic_cycle
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

FvM said:
But the thermodynamical COP is considerably above unity for the temperatures involved with an AC machine.

If we assume an evaporator temperatur of 5°C and a condensor temperature of 50°C, we get a

Carnot COP = TL/(TH-TL) = 278/(323-278) = 6.2

So even with a cheap compressor and other losses, the ratio of pumped heat to electrical input power will be in a range of 2.5 to 4.

https://en.wikipedia.org/wiki/Thermodynamic_cycle
Click to expand...

No matter how you reason it, a theoretical, unobtainable, 100% efficient AC system is going to need the amps I calculated at the voltage given in order to melt/freeze 1 ton of ice/water in a 24 hour period. Any inefficiencies in the motor, compressor, or the heat dissipation radiator is either going to require more current, or the system will be derated to less than a 1 ton cooling capacity.

Ratch
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

I think, explaining the fundamentals of thermodynamics is beyond the scope of this thread. There are so much articles on the internet.

I supplement the specification of a recent wall-mount AC (Mitsubishi MS-A12WA):

Rated capacity 12000 btu/h (3.52 kW)
Electrical Input 1070 W
Recommended fuse (115 VAC input) 20 A

Explanation for the difference between cooling capacity and electrical power, see post #14. In simple words, most of the heat to melt/freeze the said ice quantity is transferred from/to the enviroment.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

I have a 1 ton AC installed at my home which is supplied 230V using 1.5 sq.mm wires which have a current rating of 14-15A. So the Current drawing of a 1 ton AC must not be above 14-15A.
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

sharikbaig said:
I have a 1 ton AC installed at my home which is supplied 230V using 1.5 sq.mm wires which have a current rating of 14-15A. So the Current drawing of a 1 ton AC must not be above 14-15A.
Click to expand...

Interesting. Can you explain why the power to melt 1 ton of ice in 24 hours requires the full current capacity of your wiring?

Ratch
 

Re: How many amps should a one ton AC consume or usually a 1 ton ac draws how many am

Ratch said:
Interesting. Can you explain why the power to melt 1 ton of ice in 24 hours requires the full current capacity of your wiring?

Ratch
Click to expand...
That depends on how you melt the ice. If you use heat generated by simple resistance, then your calculations would be correct. That's because in resistance heating, all the heat used to melt that ice was coming purely from the electrical energy. But a heat pump is different. It uses some electrical energy together with some energy extracted from a heat sink to do its work.

I can tell you from personal experience that this is how heat pumps work. I used to have a 10kW straight resistance heat electrical furnace to heat my house. After 15 years of operation I replaced by electric resistance furnace with a ground-source heat pump furnace that took 3 kW for the same amount of heating. See the Wikipedia article on "Heat Pumps" for more information. But you are definitely wrong when you say that your calculations above establish a lower limit on how much current a 1-ton AC unit must consume.
 
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