Typical BTU Cooling Capacity Range for Air Conditioners

Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for

Single Room Air Conditioner Capacity - typically for rooms up to 20' x 20' or 400 sq.ft. in area. BTUs in this product range are typically from 6,000 BTUh to 10,000 BTUh.


Multiple Room Air Conditioner Capacity - typically for a total area of up to 800 sq.ft. BTUs in this product range are typically from 10,000 BTUh to 16,000 BTUh.

Large Capacity Air Conditioner Capacity - typically for multiple rooms or very large rooms up to a total area from 900 sq. ft. to 2,000 sq.ft. BTUs in this product range are typically from 16,000 to 28,000 BTUh.

Central Air Conditioning - typically to cool an entire floor or multiple floors in a home.
 
To determine the BTUs needed to cool a given space follow this procedure:
 
1.    Calculate the total square feet to be cooled: Measure the size of the room (or rooms) to be cooled, to obtain total square feet. Multiply room length by width for each room and if there are multiple rooms, add the room areas together to get a single number.
 
2.    Read the Base BTUs needed from Table 1 below
 
3.   Add additional BTUs for these factors:
 
4,000 BTUs for each room below a ceiling or roof which is not insulated


+ 4,000 BTUs for a home or residential kitchen included in the cooled area

+ 1,500 BTUs for each window which receives significant daily sunshine

+ 1,500 BTUs for a room over a kitchen or boiler room IF the kitchen or boiler room is actively producing heat during the cooling period

+ 600 BTUs per person over two, if more than two occupants will be occupying the room during the cooling period

4.      Subtract BTUs from the total required if these factors are present:

- 1,000 BTUs if the room is on the shaded side of the building


5.     Calculate the final total BTUh needed from the above steps. This should place you in the right range of cooling capacity needed. Review the warning below about buying an oversized air conditioner.
 
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.
 

To cool this area, look for this size air conditioner

 

100 to 150 square feet: 5,000 BTUs

 

150 to 250 square feet: 6,000 BTUs

 

250 to 300 square feet: 7,000 BTUs

 

300 to 350 square feet: 8,000 BTUs

350 to 400 square feet: 9,000 BTUs

400 to 450 square feet: 10,000 BTUs

450 to 550 square feet: 12,000 BTUs

550 to 700 square feet: 14,000 BTUs

700 to 1,000 square feet: 18,000 BTUs

1,000 to 1 400 square feet: 24,000 BTUs

High Performance HVAC Air Handler Components

Air Handler Components

This article will take different types of air handlers and disassemble them part by part to give you a good description of each part and hopefully a better understand of the air handler in general. Most of the components associated with the air handler are in the air handler. However, there are a few components which are not in the air handler but associated with the air handler. There are some hot water and cold water coils which are not fixed into the air handler but downstream in the ductwork. There are also some gas and electric duct heaters which are mounted in the ductwork and completely reliant on the air handler for air flow. These systems will also be covered and hopefully this article will offer you a comprehensive look at the air handler, all its parts, and how it functions.

The Air Handler Cabinet

The air handler cabinet is comprised of sheet metal. Manufacturers use a heavy gage sheet metal for durability and usually give the cabinet a good finish to prevent rust especially in moist environments where air handlers usually operate. The heavy gage sheet metal for durability is generally required to meet code requirements which many manufacturers try to exceed for compliance reasons. Some air handler cabinets can be disassembled and reassembled at the job site so they can fit in tight places. Another reason for disassembly is for a multi-use air handler that can be used for up flow, down flow, or for horizontal flow left to right or horizontal flow right to left. Whatever the job calls for the multi-use air handler can be quickly converted in the field without special ordering from the manufacturer.

Air Handler Plenum Transitions

When the air handler is installed the HVAC contractor has to fit the ductwork up to the new air handler. Depending on the type of ductwork and the type of air handler can depend on the type of material selected to make this transition to the ductwork. It is recommended that sheet metal be used for this transition especially if the heating system is in the air handler. If sheet metal is not used in an air handler with the heating system inside the air handler then the installation could fail a code inspection. Always read the manufacturer’s instructions on this as the temperatures inside the supply air side of the air handler can ignite combustible materials. The HVAC contractor will be fully aware of this and most contractors use sheet metal to make these transitions to other types of ductwork. If the ductwork is round then a square to round plenum transition will usually be custom made by the contractor or by a sheet metal shop which the contractor utilizes. If the ductwork is square then a plenum transition will be made to fit the air handler and the duct work together. This usually requires a highly skilled sheet metal mechanic to custom make these plenum transitions. After the plenum transitions are installed then an insulation blanket is added to the plenum transitions to ensure there is no heat loss or heat gain and also to provide a vapor barrier so that when the air in the duct work is less than the dew point temperature the duct work and the plenum transition does not sweat. It is very important to maintain this vapor barrier throughout the ductwork. If one piece of ductwork, whether this is in the plenum transition or ductwork, loses the vapor barrier it can have a domino effect throughout the whole ductwork system as moisture fills the ductwork. As the ductwork insulation gets wetter the R-value of it decreases and it begins to fall off the ductwork. Eventually all of the ductwork insulation is penetrated by moisture and the insulation needs to be replaced. If it is not replaced moisture problems occur with mold, mildew and other problems associated with moist environments.

The Air Handler Control Panel

Most air handler control panels contain high voltage and low voltage wiring, relays, and or a control board. The transformer is usually located in the air handler control panel along with either control wire splices coming from the thermostat and the condenser unit. The air handler control panel is generally the central location where the control wiring meet and are distributed to the proper locations for control. Usually, all control voltage for the thermostat, condenser, and air handler originates from the air handler control transformer. This transformer is a step down transformer which turns high voltage into low voltage. Many un-fused transformers have been burned up by homeowners who change the thermostat without first turning the power off to air handler first. Subsequently, this results in a service call to an HVAC contractor who replaces the transformer and finishes the thermostat installation. There are many different types of controls and ways to control an air conditioning and heating system and we will do our best to describe as many as possible. If you have any questions or would like to suggest a control method which you are familiar with please don’t hesitate to use our forum or the High Performance HVAC contact page to make this suggestion.

The Air Handler Control Panel: Fan Relay Control

Other components in the air handler is a fan control relay or fan control board. This gets its signal from the thermostat on a call for cooling, heating, or if the fan selector switch on the thermostat is set to the on position. Depending on the type of heating system you have the blower may turn on right away or it may not turn on right away. This small time delay for heating is to allow the heat exchanger to heat up before the fan turns on there is also a small time delay for both heating and cooling to allow for the conditioned air, whether it be heated or cooled, to be distributed throughout the ductwork and in to the spaces where conditioning is necessary. This time delay allows for the heat exchanger to cool off and for usable heat to be used in the spaces instead of letting it dissipate in the air handler or up the flue. For cooling this time delay takes advantage of a cool evaporator coil so that it can absorb a little more heat out of the air for conditioning. Some gas and oil furnaces have the heating fan control circuit run outside of the control and to a different control which is mounted near the heat exchanger and has a temperature probe which goes into the heat exchanger. This control is called a fan-limit switch and you will find it in gas furnace air handlers and oil fired furnace air handlers. This temperature probe is for heating fan control and completely bases the control of the fan on the temperature of the heat exchanger. If the temperature reaches a certain manually set temperature the fan energizes. When the temperature of the heat exchanger cools the fan de-energizes. On some of these fan-limit controllers the white wire from the thermostat also runs through these controls. This white wire controls the burner and if the temperature of the exchanger exceeds a safe limit this fan-limit switch controller will turn the burner off and keep the fan energized to dissipate the heat in the system.

The Air Handler Control Panel: Heat Relays


Depending on the type of heat (if you have a hot water boiler utilized for heating this does not apply) the air handler control panel will also have some heat relays or a heating control board to energize the heating system in the air handler. This can be a very complex circuit as it should run through several safety switches before it allows the heat relay to energize. For electric heat you should have some Klixon safety switches and a thermal safety switch which actually melts if it reaches a set temperature which is dangerous. If there is a problem with any of these switches they will prevent the air handler heating relays or control board from energizing the heat in the air handler. This is for your safety and the safety of the structure to prevent a fire or fire hazard. Some of these switches, especially in gas furnaces, are manual reset. These particular manual reset switches are generally referred to as roll-out switches as they prevent a roll-out fire fro occurring. On occasion, these switches will give you nuisance trips and its important to note the exact switch that tripped before resetting and to not reset this switch more than once. The best thing to do is to call an HVAC heating and air conditioning contractor if you have this problem or a problem with any of the safety switches. A dangerous condition may exist and if you continue to manually reset these switches you could make the problem worse.

How To Repair Room Air Conditioners

Room air conditioners, also called window units, work the same way central air conditioners do. They are smaller than central systems and often more expensive to operate. Depending on its size, a room unit may cool only the room in which it's located, or it may be able to cool adjoining rooms as well.


Sandwiched between the coils are a compressor, two fans, a motor, and thermostat controls. Dirt is the biggest enemy of window air conditioners; it can lower the efficiency of the evaporator coil, block the operation of the fan that blows out the cool air, clog filters, and block drain ports.

Both of the major components of a room air conditioner are contained in one housing.

The condenser coil faces outside, and the evaporator faces inside.

The coils, the compressor, and the motor of a room air conditioner are sealed components, so any repairs to them should be left to a professional service person. However, you can make minor repairs, and regular maintenance will keep your unit running well. When extensive repairs are needed, you can also save the cost of a service call by removing the air conditioner from its mounting and taking it to the repair shop.

During the winter, room air conditioners should be protected from the elements. Either remove the unit from its mounting and store it or cover the outside portion of the unit with a commercial room air conditioner cover or with heavy plastic sheeting, held in place with duct tape.

Caution: Before doing any work on a room air conditioner, make sure it's unplugged. Room air conditioners have either one or two capacitors, located behind the control panel and near the fan. Capacitors store electricity, even when the power to the unit is turned off. Before you do any work on an air conditioner, unplug it and discharge the capacitor or you could receive a severe shock. The unit's owner's manual will show the location of capacitors and tell how to discharge them. Otherwise, let an air conditioning technician do it.

How to Repair Central Air Conditioners

Central air conditioners have two separate components: the condenser and the evaporator. The condenser unit is usually located outside the house on a concrete slab. The evaporator coil is mounted in the plenum or main duct junction above the furnace.


Most central air conditioners are connected to a home's forced-air distribution system. Thus, the same motor, blower, and ductwork used for heating are used to distribute cool air from the air conditioning system. When a central air conditioner is operating, hot air inside the house flows to the furnace through the return-air duct. The hot air is moved by the blower across the cooled evaporator coil in the plenum and is then delivered through ducts to cool the house. When the air conditioner works but the house doesn't cool, the problem is probably in the distribution system.

Central air conditioners are made up of two separate components: the condenser unit,
located outside the house on a concrete slab, and the evaporator coil above the furnace.

Both the evaporator and the condenser are sealed. Therefore, a professional service person should be called for almost any maintenance other than routine cleaning. Central air conditioners should be professionally inspected and adjusted before the beginning of every cooling season. However, don't let your maintenance end with this annual checkup. While there aren't many repairs you can make yourself, there are specific maintenance procedures you can follow to keep your system operating at peak efficiency.

Caution: Before doing any work on an air conditioning system, make sure the power to the system, both to the condenser and to the evaporator assembly, is turned off.

CENTRAL HVAC

First things first. What does HVAC mean?


While the Energy Center usually tries to avoid the use of acronyms, HVAC is in common use in the heating and cooling industry. It stands for "heating, ventilation and air conditioning," three functions often combined into one system in today's modern homes and buildings. Warmed or cooled or dehumidified air flows through a series of tubes - called ducts - to be distributed to all the rooms of your house. A central HVAC system is the most quiet and convenient way to cool an entire home.



Unless you live in an amazingly temperate climate, the HVAC system in your home uses more energy and drains more energy dollars than any other system in your home. Typically, 44 percent of your utility bill goes for heating and cooling.


Like many other appliances, HVAC systems have improved in energy efficiency in the last decade. As a result, you can save money and increase your comfort by properly maintaining and upgrading your HVAC equipment.

Another development of the 1990s is the whole house approach to heating and cooling. Coupled with an energy efficient furnace, heat pump or air-conditioner, the whole house approach can have a great impact on your energy bills. By combining proper equipment maintenance and upgrades with appropriate insulation, weatherization and thermostat settings - properly regulated with a programmable thermostat, of course - you may be able to cut your energy bills in half.

All major appliances including gas furnaces, boilers, air conditioners and heat pumps sold in California meet the Title-24 energy efficiency standards. If you are thinking about purchasing a new central furnace, check the ENERGY STAR® database, which uses information supplied by the California Energy Commission. It displays information on most energy efficient appliances in a consumer-friendly, easy-to-use fashion.

Central Air Conditioning

Central air conditioning units are usually matched with a gas or oil furnace to provide heat through the same set of ducts.


There are also central HVAC units called heat pumps that combine both the heating and cooling functions. If you heat your home with electricity, a heat pump system is the most efficient unit to use in moderate climates. It can provide up to three times more heating than the equivalent amount of electrical energy it consumes. A heat pump can trim the amount of electricity you use for heating as much as 30 percent to 40 percent.

Even though air conditioners and heat pumps require the use of some different components, they both operate on the same basic principles.

WHOLEHOUSE FANS

Even if your home has air conditioning,
consider installing a whole house fan.
Whole house fans use far less energy
 than air conditioners and they cut
cooling costs. In fact, whole house
 fans typically use about one-tenth
of the electricity of comparably sized
air conditioners, and they are relatively
inexpensive to install. Used correctly,
they can help you cut your air
conditioning bills substantially.

Whole house fans are designed to operate in the early morning and after sundown, when the outside temperature drops below 80 degrees. The idea is to turn off the air conditioning and to turn on the whole house fan. With your windows open, fresh, cool air is drawn into your home, forcing out the hot air. Your entire house is then cooled by outside air, without the needed help of your air conditioner.

Remember not to run your air conditioner at the same time you use the whole house fan, and to keep most of your windows open when it's operating. Opening windows not only helps the air circulation, but it also prevents fumes or flames from your gas appliances and fireplace from being drawn back into your home.


While whole house fans may be placed in a number of locations, the most frequently used spot is the hallway ceiling. Louvers normally close off the fan when not in use so that conditioned air doesn't escape through it. When the fan is operating, however, these louvers open, allowing air to be blown into your attic.

Attics can be brutally hot on a summer's day. When heat is absorbed by your walls and ceilings, attic temperatures can climb to over 150 degrees. Even if your ceilings are well insulated and your home is air conditioned, this heat can seep from your attic down into your home. A whole house fan, however, draws cooler, outside air through your open windows and forces it through the attic and out through the roof vents. Your house and your attic are all cooled. Air conditioning alone doesn't offer that benefit.

Whole house fans are very powerful and need sufficient attic ventilation to be effective. Your contractor can help you determine the correct fan size, capacity and number of attic vents needed for your home.

window air conditioner

Crosley CA12ESR 12000 BTU window air conditioner

 
 
 
 
 
 




Room air conditioner by Crosley, puts out 12,000 BTU per hour and cools an area up to 490-640 sq feet.



This window unit has a pleated quick mount window kit, side louvers and handles for safe installation and service - no special tools needed and no mess in your room.


The Multi speed cooling system has a fully functional temperature sensing remote control with thermostat, 8-way direction control, an exhaust control and a fan only mode for removing circulating fresh outdoor air.

The easy access, up front electro-static filter helps remove dust and other foreign particles from the air. Just slide out for easy cleaning. The unit has a 5 ft power cord and plugs into a standard 3 prong socket and saves energy with an EER rating of 9.8, and a power-saver control that automatically turns off the compressor and fan when the selected temperature is reached and turns back on when needed.