Air Condition:
OPERATING DEFECTS - Air Conditioning System Maintenance & Operating Defects
Here we list typical, readily observed, air conditioning system operating defects.

1.)The air conditioning system will not operate at all: power may be off, controls may be improperly set, or the system may be inoperative. (Confirm that the system has electrical power and that all of its control switches and thermostat are set to "on" and "cooling" positions.

2.)The air conditioning system operates but does not produce cool air, or not enough cool air.

3.)The air conditioning system operates but there is not enough cool air flow at the registers.

4.)The compressor was short-cycling, that is, turning itself on and off rapidly, perhaps every few seconds or minutes rather than producing a normal on-cycle of 10 minutes or longer.

5.)The compressor was noisy, during startup, indicating an operating problem.

6.)The compressor squealed at startup, indicating that service may be needed promptly to prevent possibly costly damage to the system.Inspections give full detailed list of problems.

7.)Inside cooling or evaporator coil defects that can be seen by eye: dirty coil, blocked coil, frost on the coil, improperly sized evaporator coil, improper evaporator or cooling coil placement in the system.With atlanta home inspection we obsereve and field test units.
 
8.)Air flow across the air conditioning evaporator coil: if airflow is weak for any reason (dirty coil, duct system defects, blower fan defects, dirty blower squirrel cage fan), the air conditioning system will not operate properly.

Some experts write that there should be between 350 and 400 cubic feet of air per minute (CFM) moving across the evaporator (cooling) coil for each ton of air conditioner capacity. (One ton = 12,000 BTUH so if your AC unit is a 24,000 BTUH unit it is a "two ton" unit and needs to see 700 to 800 CFM of air across the evaporator coil. Our home inspectors carry a small airflow meter that can actually measure this number with fair accuracy. (The same tool is nice for comparing air flow and balancing air flow at various building supply ducts and registers.
 
9.)Evaporator coil cleaning often requires cutting refrigerant lines, removal of the coil and other components for cleaning, and reinstallation, pulling a vacuum on the refrigerant lines, and recharge with refrigerant. Such service and repair may involve significant expense, although there are some "in place" cleaning methods using foams and sprays that are a simpler procedure.

10.)Dirty air conditioning filters, - a source of increased operating costs. Very dirty filters can eventually block the fan itself, leading to more costly repairs. The filters should be changed monthly when the system is in use. Failure to properly filter dust from the return air supply can load the fan or evaporator coil with dust and prevent proper system operation. Installing a filter is normally a minor expense. Dirty, blocked evaporator coils can result in improper system operation, very low output temperatures, low air flow (compensated sometimes by increased fan speed), and sometimes frost on the coil and failure of system components.

11.)The air conditioner operates but our electrical bills are too high.

Typical BTU Cooling Capacity Range for Air Conditioners
Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for:

A) 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.
B) 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.
C) 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.
D) Central Air Conditioning - typically to cool an entire floor or multiple floors in a home. Also see A/C TYPES, ENERGY SOURCES
E) To determine the BTUs needed to cool a given space follow this procedure:
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.
Read the Base BTUs needed from Table 1 below

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
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
Calculate the final total BTUh needed from the above steps. This should place you in the right range of cooling capacity needed.Accurate home inspection we talk with client 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 ktichen or boiler room.

Table 1: Base BTUs - Recommended Air Conditioner BTUs
Number of
Rooms
Cooled Room Area
MINimum
sq.ft. Room Area
MAXimum
sq.ft. BTUs
Needed
One . 100 4,000 - 6,000
One 100 180 6,000 - 7,500
One 180 270 7,500 - 9,000
One 270 400 9,000 - 10,500
Several . 400 10,500 - 12,000
Several 400 500 12,000 - 13,500
Several 500 700 13,500 - 15,000
Several 700 800 15,000 - 16,500
Large Areas . 900 16,500 - 18,000
Large Areas 900 1000 18,000 - 19,500
Large Areas 1,000 1,100 19,500 - 21,000
Large Areas 1,000 1,100 19,500 - 21,000
Large Areas 1,100 1,200 12,000 - 22,500
Large Areas 1,200 1,500 22,500 - 24,000
Large Areas 1,500 1,700 24,000 - 25,500
Large Areas 1,700 1,900 25,500 - 27,000
Large Areas 1,900 2,200 27,000 - 28,500

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 of air conditioning. 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.

Portable or individual-area air conditioners;
Heating & Cooling units - capable of both cooling or heating a room using electricity. Basically these units are small heat pumps that are mounted in a building window or wall. Heating/Cooling units will give two different BTUh figures, one for cooling and one for heating. These figures will differ, for example, producing 18,000 BTUh in cooling mode but only 12,000 BTUh in heating mode. The difference between heating and cooling, and the amount of heat actually available will depend also on the outdoor temperatures when in heating mode (as with any heat pump system, the unit cannot provide heat below certain temperatures.)

Slider or Casement Window units - narrow tall cooling systems which are designed to fit into the narrow space provided by casement or slider windows
.
Through-wall air conditioners - air conditioning units which are designed to be installed into a metal sleeve which is then itself installed in an opening cut into the building wall, leaving windows unobstructed, or perhaps for use in a room without a suitable window in which an air conditioner could be placed. BTU output is typically a bit more than the smallest window air conditioners but otherwise is similar in range.

Portable air conditioners - units on wheels which are plugged into an outlet but can be moved room-to-room and do not require a window for their exhaust. These cooling units are of modest cooling ability, typically around 10,000 BTUh.

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