RULES OF THUMB:

1.      A ton of refrigeration (1TR) signifies the ability of air-conditioning equipment to ex tract heat@12000 Btu/hr. ASHARE  has put together a table using national average data showing the Sq-ft/Ton as follows:

Sq.ft/ton	HIGH	AVERAGE	LOW
RESIDENTIAL	600	500	380
OFFICE	360	280	190

2.      Each building is different and the design conditions differ greatly between regions to region  Factors to consider when figuring the sq-ft/ ton ratio include:

·         Climate conditions (design temperatures)

·         Expansive use of glass-particularly in the south and west t orientations

·         High ceilings-increasing the conditioned volume of the space

·         Outside air requirements-especially important in high occupant load areas like conference rooms and classrooms.

·         Heat generating equipment – example computers, copiers, laser printers, big screen TV’s etc.

·         Lighting-especially the extensive use of incandescent and metal halide lights.

·          Fluorescent lights are more efficient and burn cooler-however; their ballasts generate a fair amount of heat.      

3.      Applications and Load:

APPLICATION                                            AVERAGE LOAD

Residence	400-600 sq. ft. floor area per ton
Apartment (1 or 2 room)	400 sq. ft. of floor area per ton
Church	20 people per ton
Office Building	340 sq. ft. of floor area per ton
Large Exterior	250 sq. ft. of floor area per ton
Small Suite	280 sq. ft. of floor area per ton
Restaurant	200 sq. ft. of floor area per ton
Specialty & Variety Store	200 sq. ft. of floor area per ton
Shoe Store	220 sq. ft. of floor area per ton
Auditorium or Theatre	20 people per ton
Bar or Tavern	9 people per ton

Cocktail Lounge	175 sq. ft. of floor area per ton
Computer Room	50 – 150 sq. ft. of floor area per ton
Bank	225 sq. ft. of floor area per ton
Barber Shop	250 sq. ft. of floor area per ton
Beauty Shop	180 sq. ft. of floor area per ton
School Classroom	250 sq. ft. of floor area per ton
Bowling Alley	1.5 – 2.5 tons per alley
Small Shop	225sq. ft. of floor area per ton
Dress Shop	280 sq. ft. of floor area per ton
Drug Store	150 sq. ft. of floor area per ton
Groceries – Supermarket	350 sq. ft. of floor area per ton
Hospital Room	280 sq. ft. of floor area per ton
Hotel Public Spaces	220sq. ft. of floor area per ton

AIR CONDITIONER CAPACITY RANGES

The application and unit capacity ranges are as follows:

·         Room air conditioner - Capacity ranges 0.5 to 2 TR per unit, suitable for an area of not more than 1000 square feet

·         Packaged unit integral air-cooled condenser - Capacity ranges 3 to 50 TR, suitable for a maximum an area of 1000 – 10000 square feet

·         Split system with outdoor air-cooled condenser - Capacity ranges 0.5 to 50 TR, suitable for an area of 100 – 10000 square feet

·         Central air-conditioning chilled water system with air cooled condensers – Capacity ranges of20 to 400 TR, suitable for an area of 4000 sq-ft and higher

·         Central air-conditioning c hilled water systems with outdoor water cooled condenser – Capacity ranges 20 to 2000 TR, suitable for an area of 4000 sq-ft and higher.

COOLING CAPACITY SELECTER FOR HOMES:

Air conditioners are sized by cooling capacity in BTU's per hour. To estimate the optimum capacity for any room, first calculate the size of the area to be conditioned by multiplying its width times its length, measured in feet. Then select the cooling capacity needed using the table below, The BTU's associated with the square footage will give an approximate optimum for the space.

ROOM AREA (Sq.ft)	COOLING CAPACITY(BTU RANGE)
150	5200
200	6000
300	7500
340	8000
450	10000
550	12000
700	14000
800	15000
850	16000
1000	18000
1100	20000
1400	24000
1500	28000
1600	32000

IN GENERAL THE FOLLOWING GUIDELINES SHOULD BE NOTED:

·         500 CFM/ton for Precision Air Conditioning

·         400 CFM/ton for Comfort Cooling Air Conditioning

·         200 CFM/ton Dehumidification

SELECTION OF CHILLERS

The following is used as a guide for determining the types of liquid chillers generally used for air conditioning

·         Up to 25 tons (88kW) – Reciprocating

·         25 to 80 tons (88 to 280kW) – Reciprocating or Screw

·         80 to 200 tons (280 to 700kW) – Reciprocating, Screw or Centrifugal

·         200 to 800 tons (700 to 2800kW) – Screw or Centrifugal

·         Above 800 tons  (2800 kW) – Centrifugal

ELECTRIC UTILIZATION INDEX:

Electric utilization index (EUI) is the ratio of annual electricity consumption in kWh to the facility’s square footage.

TYPES OF BUILDING	EUI
GROCERY	61.0
RESTAURENT	38.9
HOSPITAL	16.4
RETAIL	12.1
SCHOOL	10.3
HOTEL	8.2
OFFICE	7.5
MISC COMMERCIAL	6.4
WARE HOUSE	6.1