Household Tips and Resources Rebates through Hawaii Energy Calculate Appliance Operating Costs Energy Saving for Businesses RFP - Grid Services Demand Side It's very important that you select the right sized unit for your home. An undersized unit will not have the ability to effectively handle the heat in your room, causing the unit to overwork and not perform optimally. On the other hand, an oversized unit can cool a room quickly, but can create a "cold and clammy" feel due to the humidity levels that aren't lowered properly.  We have provided a quick and easy guide to selecting a proper-sized air conditioner to fit your needs. 1. Compute the Area of the Room: Assumes an 8-foot ceiling. (Use Tab key to advance to the next field) 2. Select your Air Conditioning Needs: In what environment will you be using your air conditioner? Low Heat or Night Time Only - windows/exterior walls mostly shaded from direct sunlight, well-insulated construction.

Good figure for bedrooms or apartments in well-constructed high-rise buildings. Normal Conditions - windows/exterior walls moderately (50-70%) exposed to direct sunlight, ceiling with attic space above. High Heat or Direct Sunlight - large window and wall area exposed to direct sunlight, heavy afternoon sun, and open beam ceilings. (Use your mouse to select the appropriate choice) Low Heat or Night Time Only High Heat or Direct Sunlight Consider an Air Conditioner with a BTU rating within the range to Note: Add 4,000 BTUs if the area includes a kitchen 3. Compute the Monthly Usage Hours: How much will this unit cost to operate? The Energy Efficiency Ratio, or EER rating, tells you how efficient the appliance is in energy consumption. The higher the number rating, the more energy-efficient it is. Here is an example of how much it would cost to run your selected unit if it had an 8, 10, or 11 EER rating: Estimate length the A/C will be on:

4. Select Service Area for Monthly Energy Cost by EER: For other service areas, specify cents per kWh Your Energy Cost should be between: * EER value for box A can be changed to illustrate costs of Air Conditioners with other EER ratings. ** Default cost per kWh is based on the average residential rates for customers on Oahu and Maui Island, as of July 2008. Sizing of a room air conditioner depends on many factors, such as area of room, ceiling height, number of occupants, insulation and type of construction. We recommend you consult with the sales person at the showroom you visit to be sure that the size selected will meet your individual requirements.How to Choose an Air Conditioner Buying a room air conditioner: How big? One Size Doesn't Fit All Matching the air conditioner to the room you want to cool is your first consideration. If it's too small, it simply won't cool the space. If it's too large, it will cool the space so quickly that the thermostat will shut the unit down before it can lower the humidity level in the space.

The result is a cool room that feels damp and clammy.car ac repair durham nc Room air conditioners are "sized" according to their cooling capacity, expressed in Btu per hour. ac dc cdi unitYou'll find the rating on packaging or in product literature; window unit ac compressor wont stay onit typically ranges from 5,000 to 25,000 Btu. Units below 12,000 Btu start at $250 to $300. Those in the 12,000- to 15,000-Btu range cost from $450 to $600, while large units go up to $1,200. Air conditioners rated at 15,000 Btu should be enough to cool most rooms up to about 875 sq. ft. How do you get more precise than that? There are several different formulas. Most of the ones you'll see in stores simply compare the square footage of the room to Btu capacity.

The Association of Home Appliance Manufacturers (AHAM), a Chicago-based industry trade group, offers a more complete formula that includes window area, sun exposure, insulation levels, how the room is used and other variables. How Much Do You Need? For a calculation of the cooling capacity your space requires, use our Air Conditioning Calculator. You can get a free copy of the formula from the AHAM fax-on-demand service or through the organization's site on the Web. Although the form looks daunting, it takes only a few minutes with a calculator and tape measure to figure out the square footage of the room and measure a few other variables. Whichever way you determine the size you need, remember that for the 115V circuits typical of bedrooms and living rooms, you'll have to stay below 15,000 Btu; units above 15,000 Btu usually require a 230V circuit. And if you want to cool a large, open L- or T-shaped space, you're better off with two smaller units rather than one large one.

"The goal is to keep the cold air from pooling on the floor," explains Hank Rutkowski, director of technical affairs for the Washington, D.C.-based Air Conditioning Contractors of America. "Two units prevent cold spots in front of the air conditioner and warm spots around the corner." Where to Find It Amana Home AppliancesAmana, IA 52204800-843-0304 The Association of Home Appliance Manufacturers 20 N.Wacker Dr.Chicago, IL 60606312-984-5800 Box 4808Syracuse, NY 13221 Emerson415 Walbash Ave.Effingham, IL 62401800-332-6658 Fedders North America415 Walbash Ave.Effingham, IL 62401800-332-6658 Friedrich Air Conditioning Co.Box 1540San Antonio, TX 78295-1540800-541-6645 Whirlpool Corp.Consumer Assistance CenterBenton Harbor, MI 49022800-253-1301A 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!