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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
A/C DATA TAGS
A/C - HEAT PUMP CRITICAL DEFECTS
A/C DIAGNOSTIC FAQs
A/C TYPES, ENERGY SOURCES
AGE of CHIMNEYS & FIREPLACES
AGE of AIR CONDITIONERS & HEAT PUMPS
AIR CLEANER PURIFIER TYPES
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FILTERS for HVAC SYSTEMS
AIR FLOW MEASUREMENT CFM
AIR HANDLER / BLOWER UNITS
ANIMAL ALLERGENS / PET DANDER
ANIMAL ENTRY POINTS in buildings
ANIMAL or URINE ODOR SOURCE DETECTION
APPLIANCE EFFICIENCY RATINGS
ASBESTOS IDENTIFICATION IN buildings
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CHINESE DRYWALL HAZARDS
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
CLEANING & Legionella BACTERIA
COMBUSTION GASES & PARTICLE HAZARDS
COMPRESSOR & CONDENSING COIL, A/C
CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS
CONTROLS & SWITCHES, A/C - HEAT PUMP
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
COOLING LOAD REDUCTION by ROOF VENTS
CRITICAL DEFECTS on A/C SYSTEMS
DATA TAGS on AIR CONDITIONERS
DEFINITION of HEATING & COOLING TERMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCT SYSTEM & DUCT DEFECTS
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
DUST SAMPLING PROCEDURE
EDUCATION, HVAC SCHOOLS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRICAL POWER SWITCH FOR HEAT
EVAPORATOR COIL or COOLING COIL
EVAPORATIVE COOLING SYSTEMS
EXPANSION VALVES, REFRIGERANT
FAN, AIR HANDLER BLOWER UNIT
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FAN, COMPRESSOR/CONDENSER UNIT
FAN CONVECTOR HEATERS - HYDRONIC COILS
FAN LIMIT SWITCH
FURNACES WARM AIR HEATING SYSTEMS
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
GAUGE, REFRIGERATION PRESSURE TEST
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
HOUSEWRAP AIR & VAPOR BARRIERS
HUMIDITY LEVEL TARGET
INDOOR AIR QUALITY IMPROVEMENT GUIDE
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
MANUALS & PARTS GUIDES - HVAC
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
MOLD INFORMATION CENTER
NOISE AIR CONDITIONER / HEAT PUMP
NOISE / SOUND DIAGNOSIS & CURE
ODORS in AIR HANDLERS & DUCT WORK
OPERATING TEMPERATURES HVAC
PORTABLE ROOM AIR CONDITIONERS
PRESSURE READINGS, REFRIGERANT
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS & PIPING
RETROFIT SIZING for A/C or HEAT PUMPS
SEER RATINGS & OTHER DEFINITIONS
SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Swamp coolers: this article explains the use of an evaporative cooling system or "swamp cooler" including cool air delivery design considerations when using under-floor ducts for cool air delivery in buildings. Swamp coolers or evaporative cooling systems work well in dry climates - usually, as we explain here. The discussion of cool air duct location and routing includes general air conditioning duct design concepts that also apply to all air conditioning and cooling designs.
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The articles at this website describe the basic components of an air conditioning system and then we discuss how to estimate the rated cooling capacity of an air conditioning system by examining various data tags and components. The limitations of visual inspection of A/C systems are described. We continue to add to and update this text as new details are provided. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Evaporative coolers, also called "swamp coolers" rely on the evaporation of water to cool building air, rather than the movement of a refrigerant through cooling coils. Cooling towers, swamp coolers, and even a simple window fan blowing air across a pan of water and into a room are types of evaporative cooling systems.
[Click to enlarge any image]
Our sketch (left), courtesy of Carson Dunlop, shows three types of evaporative cooling systems or "swamp coolers".
All three evaporative cooling system approaches are similar: dry outdoor air is blown across an evaporative cooling device that uses water evaporation to cool the incoming air.
The differences among these swamp cooler designs are principally how the water to be evaporated is delivered to the evaporative cooling device (drum or pad bottom is immersed in a water reservoir pan, or a pump delivers water to the top of the evaporative pad), and the type of evaporative device itself: a rotating drum or an evaporative pad.
Delivery of Cool Air Using an Evaporative Cooling System
The link to the original Q&A article in PDF form immediately below is followed by an expanded/updated online version of this article.
Topic: Under-floor ducts for cool air delivery with (for example) an evaporative cooling system
Question: We plan to build a pilot energy-efficient home in our city. We have a long and somewhat severe cooling season, with a humidity level that is relatively low (10-15 % RH). An evaporative cooling system or swamp cooler should suffice, but there are several drawbacks: dust, open windows, safety, noise, and the like.
I would like to duct the cool air delivery system under a wood-framed floor, supplying cool air through floor registers, and exhausting it out through a roof cupola. (See sketch above, courtesy of Solar Age Magazine). I am sure that an attic fan will be necessary to drive the warm air exhaust out of the building.
Do you see any obvious problems with the scheme I have described? -- Jimmy Moore, Odessa, TX
Single-stage direct evaporative coolers, also called "swamp coolers" do provide a cost-effective means of cooling houses during hot, dry periods. Their main drawback is moister indoor air - the cost for a lower dry-bulb temperature.
Due to low energy use (for a small fan and water pump), swamp coolers are popular in the U.S. in parts of the West and Southwest. For example, our photograph at page top shows a swamp cooler system whose operating components are mounted on a Tucson Arizona rooftop.
Delivering Cool Air Through Floor Ducts?
Delivering cooled air through the floor and exhausting it through the roof runs counter to the tendency of warm air to rise and cool air to fall in a building. But an exhaust fan in the roof should pull air upwards through the entire house.
Watch out: Two warnings:
Make sure that the exhaust fan capacity in cubic feet per minute (CFM) is matched to the volume of air that is being supplied from the cooling system upwards from the floor ducts and air registers.
Carson Dunlop's sketch (left) shows a different approach for a closed air duct system that changes its duct operation depending on whether warm air or cool air is being delivered into the building.
You would probably not use this duct design in an evaporative cooling system because the evaporative cooling approach depends on continuous introduction of dry outside air into and through the building during the cooling system, but the sketch makes clear a duct system intended to deliver cool air in a building needs to operate differently than ducts intended to deliver warm air during the heating system if airflow is to be optimized.
Using a Rooftop Cupola to Exhaust Swamp Cooler-Delivered Cool Air?
Provide an air duct between the top floor ceiling grille and the roof exhaust cupola. This will keep moist (and possibly cooler) air out of the attic, where it might condense at night and cause moisture problems in the structure and in the attic insulation. (See Attic Moisture or Mold Sources and see Mold in Fiberglass Insulation. Readers ducting cool air through a crawl space should also see CRAWLSPACE MOLD ADVICE.)
Carson Dunlop's sketch (left) warns of another safety consideration: a whole house fan or an attic exhaust fan (such as we describe above), can cause back-drafting at fireplaces and atmospheric-vented gas heating appliances - backdrafting can in turn cause dangerous, potentially fatal carbon monoxide hazards in buildings.
Finally, remember to provide a means of closing off the rooftop exhaust during the heating season. Otherwise your warm house air will simply escape by natural convection currents carrying it up and outdoors through your rooftop-mounted exhaust system even if the fan is not running. See WATER & ICE IN DUCT WORK for a case history where just this problem occurred in a building.
When is Evaporative Cooling Effective
See Solar Age Magazine "Notebook" 2/84, for the conditions where evaporative cooling is effective. In that issue, author Jerry Germer reviews use of the psychrometric chart that relates moisture, temperature, and indoor relative humidity to discuss the conditions that make people comfortable indoors, and how to relate indoor comfort to the outdoor climate, particularly to temperature and humidity in those two environments.
Our photo (left) shows an evaporative cooler or "swamp cooler" in use blowing cool air into an outdoor mechanic's work area at Canyon Auto Sales in Tucson, AZ. Photo by the author and Andy Gieseke, Canyon Auto.
Swamp coolers or other evaporative cooling systems can cool a building interior using less energy than a conventional air conditioner or heat pump system except during times of very wet or humid weather such as the "monsoon" season in southern Arizona. During wet and very humid weather evaporative cooling simply cannot evaporate enough water to produce good cooling. Some building owners install both evaporative cooling or swamp coolers and a conventional refrigerant-based air conditioner or heat pump, running the latter only when necessary due to humid conditions.
Watch out: leaky swamp coolers or just about any mechanical equipment that regularly spills or overflows water onto a roof surface is likely to cause stains on the roof surface and might lead to roof wear as well. Details are at WHITE STAINS on ROOFS.
8 Indoor Air Cooling Strategies
Mr. Germer mapped eight heating and cooling "design zones" onto areas of the psychrometric chart and then described eight indoor air conditioning approaches and related them to the outdoor climate. For areas or times of the year when temperature and humidity outdoors, and thus also relative humidity, fall within multiple zones on the Germer chart, multiple of the 8 zones and 8 indoor air conditioning strategies below might be usable.
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