Written Upvoted by Loring Chien, Written You will find the below link very informative in regards to AC power and efficiency information (India-centric)Air conditioner selection: understand Tonnage, EER, COP and Star RatingIn simple termsI ton AC will remove heat equivalent to melt 1 ton of ice in 24 hoursThis is equal to 12000 BTU (British Thermal Unit) per hourThis is the cooling capacity rating found in most International (non Indian) AC specification sheets and websitesThis is equal to 3517 Watts per hourThis is the cooling capacity rating found in most Indian AC specification sheets and websitesBe aware... Of course, there are more than 3 reasons that your 3 ton air conditioner isn't really 3 tons, starting with the fact that it's not 3 tons in weight. That unit refers to cooling capacity and harkens back to the days of ice. I'm also not talking about any of the multitude of reasons having to do with improper design, faulty installations, or lack of maintenance, topics that I discuss plenty in this space.

No, today I'm going to tell you that your 3 ton (or 2 ton or whatever size you have) air conditioner may not be what you think it is even when everything's designed, installed, commissioned, and maintained perfectly. David Butler wrote about two of these reasons in a guest post on ACCA's Manual S protocol for selecting HVAC equipment two years ago, and that's a great article for understanding some of the subtleties. So, what are these 3 reasons? The first reason is that when we talk about air conditioner capacity, we're usually giving the nominal size. A 3 ton air conditioner has a nominal capacity of 36,000 BTU per hour, but the actual rating using the operating conditions specified by AHRI is rarely the same as the nominal capacity. For example, the AC shown in the AHRI certificate below is a 3 ton air conditioner (36,000 BTU/hr) with an actual capacity of 2.8 tons (34,000 BTU/hr). As David Butler discussed in his article on Manual S, AHRI ratings are done for an indoor dry bulb temperature of 80° F and indoor wet bulb temperature of 67° F. ACCA recommends using an indoor design temperature (dry bulb) of 75° F and relative humidity of 50%.

That's closer to the actual conditions that most homes actually operate at than AHRI's conditions. Let's think about the temperature difference and see what effect that might have on the cooling capacity. cost to move outdoor ac unitWhich way do you think it would go if we bring cooler air into the air conditioner than it was rated for? ac units for cheapWell, let's frame that a little differently. ac power supply ukIs it harder to cool cooler air or warmer air? The answer is the former. The lower the temperature goes, the harder it is to remove more heat from it. Just ask the folks at the Microkelvin Laboratory at the University of Florida, where they get about as close to absolute zero as is possible. If it's harder to cool air at 75° F than air at 80° F, then that means the 2.8 ton air conditioner above isn't even going to be 2.8 tons.

To find the answer here, you have to factor in the humidity levels, too. As David wrote, it's a moving target, but the net result of AHRI's operating conditions is that your air conditioner's capacity is lower than it's rated (unless you keep the thermostat at 80° F or higher). AHRI uses 95° F as its outdoor test temperature, so if your outdoor cooling design temperature differs from that, your AC capacity will again vary from the AHRI rated capacity. In this case, we get a little of that lost capacity back here in Atlanta. Our design temperature is 92° F, which means that the air conditoner has an easier job of dumping heat into the outside air than it would if it had to dump the heat into 95° F air. If you live in Tucson, Arizona, with a design temperature of 103° F, however, your 3 ton air conditioner has now dropped in capacity again. It's just harder for that refrigerant to give up those BTUs to air that's hotter. It's important to remember that the three reasons above don't have anything to do with poor design, installation, commissioning, or maintenance.

Plenty of other factors related to those issues also affect capacity: These are not good reasons to oversize an air conditioner! The main thing to be aware of is that you need to know more than just the result of the Manual J cooling load calculation. A Manual J report may say you need a 3 ton air conditoner, but for the three reasons above, you might really need to install a 3.5 ton unit. That's why Manual S, the equipment selection protocol, is so important. The thing is, though, that even with these issues that mostly reduce the capacity of your your air conditioner, most air conditioners still end up oversized. I recently heard someone say that thumbs are great things, but it's good to recognize their limitations. Having opposable thumbs allows us to write a letter, examine a mulberry, and hold a glass of beer, but no matter how great they are, they can't design HVAC systems. Rules of thumb don't work. You need to know how things really work and do the math for that.

What Exactly is Manual S in HVAC Design and Why Is It Important? The Magic of Cold, Part 2 - Intermediate Air Conditioning Principles , used under a Creative Commons license. 24,000 BTU 2 Ton Ductless Mini Split Air Conditioner and Heat Pump - 220V/60Hz Ductless mini AC system with a heat pump for the winterRamsond Ductless (Duct-Free) Mini Split Air Conditioning Systems can be installed in virtually any location. Ductless Mini Split Air Conditioners are also referred to as Zone Systems. They cool/heat the zone or areas in which they are installed. When the zone is in use, the mini split system can be turned on. When the zone is not in use, you can simply turn it off. This zone capability allows for substantial energy savings. Ramsond Heat Pump systems not only provide cooling during the hot summer months, but also provide efficient heating for the winter. They are far more efficient and substantially more economical compared to conventional central air conditioning systems.

Ductless Mini Split systems are comprised of two main components: 1) The outdoor unit (Condensing Unit), and 2) The indoor unit (Evaporator Unit). The installation is simple. The indoor unit hangs on a metal bracket (supplied) that attaches to the interior wall, much like a picture frame. A 3 in. hole is then drilled through the wall. The Line set and communication wires are passed through this hole and connect the indoor and outdoor unit together. The Main power is supplied to the outdoor unit. The indoor unit draws its power from the outdoor unit. The system is operated by a wireless remote control (supplied). Simply set the remote control to the desired temperature and the system maintains the desired temperature. Capacity: 24,000 BTU (2 ton) cooling 24,000 BTU (2 ton) heating (heat pump) + 1000-Watt electric back up heating Power requirements: 220-Volt/60Hz, single phase powered from the outdoor unit Area coverage: up to 1200 sq. ft. Functions: cooling, independent dehumidification, and heating (heat pump)

Efficiency rating: high efficiency (SEER 13.0) Refrigerant: pre-charged with environmentally-friendly DuPont R410A refrigerant Complete system: includes indoor unit, outdoor unit, complete installation kit, 25 ft. of insulated copper line set, remote control Quiet operation: low noise, includes sleep function Easy installation: includes installation kit; quick install system: pre-wired indoor unit (25 ft. cable) with quick connection; pre-flared and flanged insulated copper line set kit; quick install system cuts installation time in half Features: indoor unit digital display of temperature (degree Fahrenheit), functions and error messages; auto-restart: in case of power outage, the system restarts automatically to previous settings; self-diagnostic system: in case of malfunction, the indoor unit display shows error message codes; 24 hour start/stop timer; multi-directional oscillating indoor unit louver Multi-function digital wireless remote control with wall-mount cradle/holder