From 1st September 2016 EVERY product we sell now has a standard THREE YEAR WARRANTY Home  »  Cooling Calculator Please make sure you fill in all the boxes marked with a *. Average number of people in room: Number of computers, printers, etc: Does your room have south facing windows?:Air conditioner BTU requirements: this article provides an air conditioner BTU chart shows how to choose a room air conditioner for window or through-wall mounting. We provide room air conditioner or window air conditioner BTU sizing & choice charts. We also show how to actually calculate how much BTU cooling capacity you need based on building area or square feet, and we warn about dehumidification problems if you buy an air conditioner that is too big for the space you are cooling. Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for: The table below gives recommended air conditioning BTU's necessary to cool a single room.

The data in the table assumes that the ceiling over the room is insulated and that the room is not over or is not itself a special heat-producing area such as a kitchen or boiler room. Table 1: Base BTUs - Recommended Air Conditioner BTUs Calculating BTU Requirements: instead of using the table above, and particularly where factors may make the table inadequate (examples are given just below) you may want to CALCULATE the BTU COOLING REQUIREMENT using the procedure given below in this article.used heating and air conditioning units for sale Ceiling height variations: BTU capacity tables for air conditioner selection typically assume typical 8 foot ceiling heights in residential spaces. running an ac unit insideIf your ceilings are significantly higher, say 14 feet or more, you may want to use the next larger room area size when selecting the BTUh capacity needed for your air conditioner, particularly if your building is located in a hot climate with higher heating loads.ac unit motor price

Building heat gain rate variations: in locations of high heat gain or high solar gain such as a significant exposure to direct sunlight or many sun-facing windows, or for buildings with little insulation, you may need to select a higher-capacity air conditioner than given by the table.of a typical home can be cooled per ton of cooling capacity: that is, one ton (or 12,000 btuh) of air conditioning can cool about 500 sq.ft. But the real answer is, it depends. Some of the factors that affect the ability of an air conditioner to cool a space need to be considered besides just the number of square feet. These include at least the following questions about air conditioning load and cooling requirements: Watch out: Do not buy an air conditioner which is oversized (too many BTUh) for the area you need to cool. You may think that bigger is better, but not in the case To make a room comfortable the air conditioner needs to both cool the room air AND dehumidify the room air.

If the air conditioner is too large for the space to be cooled, the temperature will drop quickly and the A/C unit will shut off before the air has become adequately dry. The room will be either too cold or too humid for comfort. Sketch courtesy of Carson Dunlop Associates. More detail about how to diagnose and cure an air conditioner that is not dehumidifying can be found at DEHUMIDIFICATION PROBLEMS Continue reading at BTU SIZING FAQS for AIR CONDITIONERS or select a topic from the More Reading links or topic ARTICLE INDEX shown below. Or see DEHUMIDIFICATION PROBLEMS Or see PORTABLE AIR CONDITIONER BTU CHART for portable room air conditioner BTU sizing advice.A question I pose to the attendees of each mini split class I conduct is: Can you oversize an inverter ductless mini split system? Before you start writing your reply to what I’m sure you think is an obvious answer, let me save you the effort — yes — the answer is yes, of course you can!

Gerry Wagner’s testing lab for Comfort-Aire mini split products.   Now, with that out of the way, let me address why I pose the question at all if it’s so obvious. We need to start with the anatomy of an inverter system. An inverter compressor can run at 3,600 RPM like every other compressor in HVACR equipment, but the difference is that it doesn’t have to. Let me digress a moment… I'm a “wet-head” by birth. Being from the New Jersey and New York area, hydronics is the first HVACR subject you learn about, and then air comes later. When I started in the boiler biz back in the 1970s, we made a lot of different boilers: 50,000 Btuh, 75,000 Btuh, 100,000 Btuh, 125,000 Btuh, 150,000 Btuh, and on and on. Today boiler companies, for the most part, make one boiler, a modulating boiler that can down fire to as low as 50,000 Btuh and modulate up all the way to 150,000 Btuh. If you install this boiler in a home with a heat loss of 100,000 Btuh it doesn't short-cycle because it will never produce anything over 100,000 Btuh.

Because it measures indoor and outdoor ambient air temperature and fires the boiler accordingly. Now you can take that old, oversized non-modulating 150,000 Btuh boiler, in a home with a heat loss of 75,000 Btuh, and stop it from short cycling by adding indoor/outdoor reset to the control system. Instead of heating the water up to 180°F even when the outdoor temp is 50°F and you just need to take the chill off, the control will fire the boiler only up to the temperature required to meet the heat loss of the home based on the outdoor air temperature. There would be some mechanical changes required, specifically a bypass from the boiler supply to the return to make sure a minimum return temp came back to the boiler to prevent thermal shock. New condensing boilers don't require a bypass as the lower the return temperature the more efficient they run. So why am I giving you the Hydronics 101 lesson? Well, because the same principle applies to an inverter compressor. Wagner conducts a course sponsored by Comfort-Aire and Heat Controller Inc.  

The inverter compressor does not start at 3,600 RPM and then ramp down as the system finds the set point programmed by the homeowner. It starts at the lowest RPM and ramps up. If the actual room temp and the setpoint are only a few degrees apart, then the compressor will never come anywhere near full capacity. Like the modulating boiler, the inverter system senses both indoor and outdoor temperatures and applies power to the compressor accordingly, (the compressor is the burner, if you will).   The test lab I can prove it very easily. My test lab here in New York is a 10-ft. x 20-ft. prefabricated garage where Itest mini split products on a consistent basis with multi zone and single zone inverter systems, both cooling and heating. . . This building contains radiant floor heating, (slab on the first floor, joists on the second), with a Pulse condensing boiler and a small duct high velocity air conditioning throughout. [Wagner’s home is also heated via radiant flooring, a thermal solar system for domestic hot water, and an oil fired boiler is used as the heat source, plus, small duct high velocity for air conditioning.]

A recent equipment test had me install a single 12,000 Btuh inverter ductless system in the lab. Rather than short cycle as you would expect, what happens is the system rarely shuts off. The compressor will initially, (over a three minute period, if needed), ramp up to full capacity and get the room to the programmed set point and then you will see the compressor ramp down to a minimum running RPM. If the fan is on auto, it will do the same. The compressor may shut down completely and the controls programmed into the equipment will keep the compressor off for a minimum of three minutes and then it takes another three minutes for the compressor to come back up to full capacity. A minimum cycle (if it existed) could be no shorter than three minutes. Inside the lab two 9K evaporators are tested. You can further increase the run cycles by placing the evaporator fan in the manual mode and operating it at the lowest speed. What always has to be considered when dealing with inverter ductless mini splits is the range of operation that the system will provide.

Unlike a conventional system that only knows two performance points, on and off, the inverter offers a range of performance. A 9,000 Btuh inverter evaporator will give you an operating performance range of approximately 2,000 Btuh to 11,000 Btuh of cooling. A 12,000 Btuh inverter evaporator will give you an operating performance range of approximately 3,000 Btuh to 13,000 Btuh of cooling. An 18,000 Btuh inverter evaporator will give you an operating performance range of approximately 7,000 Btuh to 23,000 Btuh of cooling. Two ways to oversize Let’s look at an example. If you install a 9,000 Btuh inverter evaporator in a room that has a heat gain of 5,000 Btuh, will it ever produce 9,000 Btuh? It will ramp up to 5,000 Btuh and satisfy the set point programmed by the homeowner and then maintain that set point thereafter. So, with this in mind, back to my original question: can you oversize an inverter ductless mini split system? Well, I believe there are two ways to oversize utilizing an inverter mini split.

The first is the obvious capacity oversize. Let’s use the same example of a room with a 5,000 Btuh heat gain. If you install an 18,000 Btuh inverter evaporator in that room, are you oversized? The low end of the performance range of an 18,000 Btuh inverter evaporator is 7,000 Btuh — more than the total heat gain of the room. Where I see installers make a less obvious mistake in sizing inverter mini splits is with this scenario.  Again, the room with the 5,000 Btuh heat gain, but now we have an installer who decides to install a 12,000 Btuh evaporator in the room saying to himself, “It’s an inverter, it won’t ever go up to 12,000 Btuh because the room only needs 5,000 Btuh … so what’s the harm?” Under normal conditions the unit will never go beyond 5,000 Btuh, but the harm is that his competitor who makes the more accurate choice of a 9,000 Btuh evaporator for the same room will get the job based on equipment cost alone!  Keep in mind, that the appropriate 9,000 Btuh evaporator will still allow an additional 6,000 Btuh of capacity beyond the room’s calculated heat gain of 5,000 Btuh should your customer decide to have a keg party in the room on the 4thof July and invite all his or her sweaty friends!