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BLOWER FAN OPERATION & TESTING
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BTU USAGE MONITORS
CARBON MONOXIDE - CO
CIRCULATOR PUMPS & RELAYS
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DRAFT REGULATORS, DAMPERS, BOOSTERS
DUCT SYSTEM & DUCT DEFECTS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
FAN, AIR HANDLER BLOWER UNIT
FLOODED HEATING EQUIPMENT REPAIR
FLUE SIZE SPECIFICATIONS
GAS BURNER Flame & Noise Defects
GAS PIPING, VALVES, CONTROLS
GEOTHERMAL HEATING SYSTEMS
HEAT PUMPS, DIAGNOSIS, REPAIR
HEATING COST SAVINGS METHODS
HEATING OIL PIPING TROUBLES
HEATING OIL TANKS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
GAS LP & NATURAL GAS SAFETY HAZARDS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
MOTOR OVERLOAD RESET SWITCH
NOISE, HEATING SYSTEMS
ODORS FROM HEATING SYSTEMS
OIL FILTERS on HEATING EQUIPMENT
OIL FILL PIPE LEAKS
OIL SPILL CLEANUP / PREVENTION
PLASTIC Plexvent / Ultravent RECALL
PUFFBACKS, OIL BURNER
RELIEF VALVE LEAKS
Reset Switch - Heater Primary Control
RESET SWITCH - ELECTRIC MOTOR
Reset Switch - Stack Relays
SAFETY, HEATING INSPECTION
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOLAR HEATING SYSTEM DESIGNS
SOOT on OIL FIRED HEATING EQUIPMENT
STEAM HEATING SYSTEMS
THERMOSTATS, HEATING / COOLING
VIDEO GUIDES: Heating System Videos
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
ZONE VALVES, HEATING
This article discusses methods for providing adequate, safe combustion air for fuel-burning appliances in tight buildings - how to provide outside combustion air for heating appliances.
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Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
This article explains the need for adequate combustion air for fuel burning appliances in buildings, for both safety and for proper equipment operation. Figure 1 (page top and shown in more detail here) notes that by confining the gas furnace in a separate room, adequate air for draft and combustion can be supplied [from outdoors] without adding infiltration to [and cooling] the house. The author notes that
Simple Homeowner Tests for Adequate Combustion Air & Adequate Chimney Draft
An easy test of adequate draft in a gas appliance is to hold a just-blown-out match near the vent hood and see if the smoke is drawn up the flue. This chimney draft test should be performed under worst conditions: in warm weather (the chimney stack pressure will be lower in warm weather), with the house closed up (shut windows and doors, especially the windows and doors feeding the utility room where the appliance is located), and running all of the building's exhaust fans at once.
See BACKDRAFTING HEATING EQUIPMENT for a detailed description of the test procedure to check for adequate combustion air and adequate draft.
Two Methods for Supplying Combustion Air for Heating Appliances in Tight buildings
The National Center for Appropriate Technology (NCAT) [and other sources such as the Uniform Mechanical Code and the National Fuel Gas Code] suggest looking for carbon build-up around the burner and looking for flue corrosion. Two approaches are given for supplying outdoor combustion air to fuel-burning (oil, gas, wood, coal) heating equipment:
Direct-Vented Combustion Appliances
Some heating appliances, furnaces, boilers, and water heaters, are designed to isolate the combustion process from the living space entirely, avoiding the need for complex combustion air and venting schemes.
Direct-vented combustion appliances are designed and tested to burn fuel and draw combustion air properly even when high winds hinder draft. Typically such systems include two sets of piping or ducts between the appliance and outdoors, one bringing combustion air in directly to the appliance burner, and a second venting combustion air outside. The two vents might appear on some systems as a single larger diameter double-walled pipe containing actually two vents, the smaller located inside the larger.
Combustion Air for Air Tight Woodstoves
Typical airtight woodstoves require only 10-25 cfm of combustion air - much less than an open fireplace (50 to 150 cfm or more) or to older non-airtight woodstove. But in tighter homes it may be necessary to provide combustion air or a draft inducer fan even for these appliances.
Just as modern energy codes provide a vent to supply outside air to open fireplaces, outside combustion air can be supplied to an airtight woodstove through a floor vent or a wall register that is ducted in turn to outdoors - a method that adds to cold air infiltration into the building.
A more promising approach described in the original article Combustion Air Details for Tight Houses(page 3) [PDF] is to supply combustion air through fixed ducts right to the appliance air inlet.
See COMBUSTION PRODUCTS & IAQ for the relationship between fuel burning appliances and building indoor air quality. More about carbon monoxide - CO - is at CARBON MONOXIDE - CO and at CARBON MONOXIDE WARNING.
Also see the safety warnings at BACKDRAFTING HEATING EQUIPMENT.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Original article in PDF form:
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