Mechanical Engineering.

If its too heavy to carry up the stairs with two people to your apt. then, the tonnage is too high. If you stand in front of it and you nose falls off, the tonnage is too high. If the the sill of your window sags from the weight, your tonnage is too high. If the lights of the power station dim when it turns on, your tonnage is too high. If the plants next door have frost bite, then your tonnage maybe just a little high.

Air cons, for household, use are usually measured in BTUs. Most places will do just fine with 100- 150k machines.

What I think you mean is " Is it working all right?" The name plate on the equipment is correct. It will give the rating of the equipment. To determine if it is working correctly is another problem best left to the experts. It is not just a matter of adding gas (refrigerant) you need to know a lot of information to determine if it is operating correctly.

To get this information, will require a number of tools. Amp-volt meter, Refrigeration gauges, a pressure temp chart for refrigerants and experience,(this tool is not for sale it is always on back order and take a long time to get it)

What can you do?

1. Make sure you have Clean filters
2. clean coils (condenser and evaporator)
3. If you have a belt driven fan, make sure it is tight.
4. If your return line at the compressor is wet with condensation , then it could be working OK.

Del

People go to school for a year or two including regular hands-on training to do just you asking about. Go with a professional. Too many variables and what ifs.

Breaking your question into two parts. You said:I need a calculation to measure the tonnage of 5 tons A/c in my apartment.

The term ton as applied to air conditioning is the ability to take 2000 pounds of 32° water and convert it to 2000 pounds of 32° ice in a 24-hour period. This change of state requires approximately 288000 BTU's divide that figure by 24 hours and you end up with 12,000 BTU. 5ton's= 5x12000 BTUs = 60,000 BTU per hour.

Airflow as applied to standard air conditioning units is typically 400 CFM per ton of capacity. So in the instance of a 5 ton unit the airflow is 2000 CFM.

You said:I need to know wheather I am getting the right cooling or not.

Dellori3 has posted the standard maintenance procedures along with asking you to check and see if the suction line (larger of the two lines) is sweating, that would be a good place to start.

Although you could calculate the actual performance of the unit, by measuring the Delta T., airflow and relative humidity is not necessary.
Besides the maintenance procedures already mentioned there is one other easily perform test.

Set the thermostat on a cool call and wait about five minutes for the unit to stabilize. With a accurate thermometer measure the air temperature returning to the unit, next measure the discharge air temperature by placing your thermometer in a supply registered as close to the unit as possible, or if possible directly in the supply Plenum.

Subtract the supply air temperature from the return air temperature, if you end up with a difference somewhere between 17 and 20° Fahrenheit the unit is probably functioning correctly. If the Delta T. is above the 20° mark the airflow is probably restricted by either a dirty coil, clogged filter, or if it is belt driven a loose belt. If the Delta T. is below the 17° mark the unit is probably not functioning correctly i.e. low on charge plug condenser coil, or some other mechanical problem. If that is the case it is best to call a qualified servicemen.

PS the Delta T. temperature figures are approximate, and will vary with humidity. The further out of the 17 to 20° range the more likely it is that the Unit isn't functioning properly.

I advise you simply to use the following thumb role equation to check whether you have the right capacity A/C unit or not:

Measure LxWxH of the room to be air-conditioned in cubic feet, and divide it by 1200. You will get the cooling tonnage required. For your information, this will also be applied if you have many rooms in the same apartment, and using ducting system, just do the same calculation, and add up the result to get the total tonnage capacity.

For checking the efficiency and performance of the A/C unit, just observe the unit while on operation in full load, and thermostat is set to the middle, whether it stops and starts periodically or not. If yes, then the unit is correctly sized, and performing well. If not, and the unit keeps running without stopping,then the unit is under sized, or having a technical problem like filter clogged with dust, or insufficient refrigerant charge, or condenser coils not sufficiently cooled....etc.

Where are you or square footage of apt? Ceiling height? Average humidity? And how cool do you like it? Window air? Central air?

Well..all many have given different dimensions to the problem..However i feel before knowing the tonnage of airconditioning system one should know about the heat load both sensitive and latent.Thumb rules may not give proper result.Knowing the heat load,Delta T,Volume of room are some of the key factors to be considered before designing A/c system.

Thumb rules always based on all such labourious and lengthy calculations, and its applications have been proved good and satisfactorial.

Thanks.

How to size A/C ? Usualy you can calculate as follows: Square feet X 25= BTUH

BTUH/12,000 = tonnage

To control A/C , Go to: www.kunne.us

Also, www.palmbeachrd.com

Teppo K. Jokinen ( BSME )

The easiest thing to do is to check the temperature difference between the return air and the supply air when running. Usually the return is where your filter is. You would like around a 20 degree F difference between he two, if not then hen you might have problems, either with the unit sizing, or the units charge or restrictions in the air flow some where.

Jim

Hi¡

heating/cooling requirements can be estimated your with following rough numbers (just average values)

Heating: 80 W/m2 (soft cold weather) - 120 W/m2 (hard cold weather)

Cooling: 55 W/m2 (soft warm weather) - 85 W/m2 (hard warm weather)