COMBUSTION SAFETY Why Combustion Safety? … · Why Combustion Safety? • Hydrocarbon fuels are...
Transcript of COMBUSTION SAFETY Why Combustion Safety? … · Why Combustion Safety? • Hydrocarbon fuels are...
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COMBUSTION SAFETYBASICS
Joe Konopacki
Why Combustion Safety?• Hydrocarbon fuels are hazardous
– Explosion or fire is possible
– Poor indoor air quality
• Exhaust byproducts are harmful or deadly– Safe and efficient combustion
– Proper exhaust management
• Fire hazards happen thoughtlessly– Combustibles set near fire
• Our clients want a safe & healthy home– Communicate the level of risk & required action
Combustion Safety Basics
What to look for
• Ambient (breathing zone) CO
• Gas/fuel Leaks
• Combustion Air
• CO production (on all gas appliances)
• Exhaust Spillage signs
• Dryer Safety
Combustion Safety Basics
Combustion Process & CO
• CH4 + 2O2 →
• Combustion is rarely perfect
Combustion Safety Basics
2 H2O
CO2
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CO Production
• Lack of oxygen = Incomplete combustion
• Inadequate combustion air
• High gas pressure
• Dirty, Misaligned burners
• Flame impingement
• Back drafting of combustion byproducts– Carbon Dioxide (CO2) -- Nitrogen Oxide (NO)
– Carbon Monoxide (CO) -- Sulfur Dioxide (SO2)
Combustion Safety Basics Ambient (breathing zone) CO
~3 yr Sensor Life!
CO Alarms
Ambient CO Monitoring – CO Alarm
• Young, old and ill feel
effects first
• >5ppm can affect a fetus
• Position near source
Ambient (breathing zone) CO
CO Detectors
• ~3 year typical sensor service life
• Some claim 10 year service
• ‘TEST’ is for
the battery,
not the sensor
Ambient (breathing zone) CO
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Ambient CO Monitoring – CO Detector
• From time of entry
• BPI Ambient Limit: 35 ppm
• Ventilate
• Determine source
Ambient (breathing zone) CO
Detecting Gas Leaks
• “Zero Out” Outside – or not?
• Adjust/Check Sensitivity
• Slowly move sensor around joints
• Check all accessible fuel pipe and
joints
• Don’t move appliances
• Natural gas rises↑ - Propane falls↓
Gas/fuel Leaks
Reporting Gas Leaks • Confirm with soap bubble
solution?
• Tag it & Photo
• Leave a notice for homeowner
• Call out Pre-1973 Brass gas lines
Gas/fuel Leaks
Gas Leaks
• Most common issue
• Typical – 1 leak per house average
• Not ‘Normal’
• Symptoms
– Respiratory allergic reactions
– “Mold allergies”
– Respiratory sensitivity
Gas/fuel Leaks
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Combustion Air from Inside
Combustion Air
Total BTU to Volume of space
100,000 ��� �� × 50� �
1000 ���/��= 5,000 � ��
625 ft2 x 8’ tall space
Combustion Air from Outside
Combustion Air
1 ��. �� �� �������
2� ���/��
1 ��. �� �� �������
1.5� ���/��
Gas Oven Testing
Gas Oven CO Measurement
• Open window and/or turn On exhaust fan
• Test CO level in flue (undiluted stream)
• Set oven at highest setting (Broil)
• Monitor ambient CO during test (~2 ft away)
CO Production
Gas Oven TestingCO Production
Steady State
Over 100 ppm is excessive
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Gas Oven TestingCO Production
Gas Oven CO Measurement• Record CO level at 10 minutes (Steady State)
• Report CO profile
• Recommend clean, tune & re-test
• Use exhausting range hood
• Typical high CO source in homes
Gas Oven TestingCO Production
Types of Exhaust
Atmospherically vented
• Natural Draft
• Uses metal exhaust pipe
• Inside air for combustion
• Hot exhaust rises due to greater buoyancy
• Open draft hood for dilution air
• Spillage possible here
Combustion Safety Basics
Types of Exhaust
Induced Draft or
Mechanically Assisted
Combustion Safety Basics
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Types of Exhaust
Atmospherically vented
• Induced Draft or Mechanically Assisted
• Uses metal exhaust pipe
• Inside air for combustion
• Fan pulls combustion air through heat exchanger
• Fan does not push exhaust up and out
Combustion Safety Basics
• Under or through draft hood
• Access undiluted flue gases
Combustion Safety Basics
Measure CO
Types of Exhaust
• Power Vented = 1 PVC pipe
• Inside air for combustion
• Cool exhaust pushed out
• Direct Vent = 2 PVC pipes
• (a.k.a. Sealed Combustion)
• Outside air for combustion
• Cool exhaust pushed out
• Check CO outside
Combustion Safety Basics
Types of Exhaust
Power Vented = 1 PVC pipe
Direct Vent = 2 PVC pipes
Combustion Safety Basics
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Types of Exhaust
Combustion Safety Basics
• ¼” rise per foot min. for horizontal
• Min Vertical Rise (typically 3x vent diameter)
• With commonly vented units:
– Smaller Btu unit vented Above Larger Btu unit
– A Y-fitting assists natural upward draft
– Smaller unit Y’s into Larger unit
Proper Venting
Combustion Safety Basics
Improper Venting
• Blocked, or partially blocked, chimneys, vents
or vent connectors
• No chimney liner for orphaned water heaters
• Improperly designed vent system
– An indirect route
– Negative slope
– T-fittings
• Lack of code compliance
Combustion Safety Basics Combustion Safety Basics
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Combustion Safety Basics Combustion Safety Basics
Combustion Safety Basics
Improper VentingCombustion Safety Basics
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Stack Effect
House PressuresCombustion Safety Basics
•Creates negative pressure low in home
•Driven by temperature difference to outside
•Greater Stack pressure requires greater Draft pressure
Wind Effect
House PressuresCombustion Safety Basics
•Positive pressure on Windward side induces spillage
•Negative pressure on Leeward side induces draft
Make note of:•Wind direction & speed•Location of Flue
Mechanical Fans
House PressuresCombustion Safety Basics
•Bath & kitchen fans (30-1200 cfm)
•Clothes Dryer (100-150 cfm)
•Wood/gas burning stoves & fireplaces (300+ cfm)
•Whole-house fan (1000-5000 cfm)
This is whatleaky ductwork
can doto your house
Combustion Safety Basics
Supply Leaks
Return Leaks Room Imbalances
No Leaks
Consider:
•Air Handler
•Duct Leaks
•Supply/Return Distribution
•Door Closures
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House Pressures
Combustion Safety Basics
House Pressures
Combustion Safety Basics
Depressurization Limit
Limit is:
• Low for weak draft appliances
• High for stronger appliances
• Tug-of-War handicap
Exhaust Spillage Signs
Negative
CAZ Pressure
Negative
Draft Pressure
Occasional Exhaust Spillage
Exhaust Spillage Signs
•Large exhaust fans
•Wind on chimney
•Room pressures
•Flue obstruction
•Flue geometry
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ConsistentExhaust Spillage
Exhaust Spillage Signs
• Clogged flue
• FAU pressures
• Open returns
• Duct leaks
• Constant exhaust fans
• Tight home
Worst Case Pressure Testing
The goal is
to make the appliance fail.
If it can be done on purpose,
the homeowner may do it by accident.
So how much negative pressure
is too much?
Exhaust Spillage Signs
Typical
Worst Case Depressurization
Exhaust Spillage Signs
Pressure Limit = -5
CDL Exceeded-FAIL-
• Fire appliance & check for spillage for 1 minute
Spillage TestExhaust Spillage Signs
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Dryer Safety
Dryer Safety
• Vinyl or metalized Mylar will burn
• Fire hazard with gas dryers
• Recommend:
• Install metal – flex or solid
• Clean entire line of lint
• No CO testing
Issues to Look For
Combustion Safety Basics
Dryer exhaust duct material
Gas leaks
Oven CO/ Range hood venting
Combustion air requirements
Melted grommets on water heater
Corrosion near draft hood
Evidence of flame roll out
Benefits of CO Test
Combustion Safety Basics
• Detect…
• Dangerous CO
• Malfunctioning unit
• Inefficient unit
• Cracked heat exchanger - $$
• Recommend further analysis & repair
Benefits of Combustion Safety Basics
Combustion Safety Basics
•Better understanding of house pressures on combustion exhaust flow
•Safety issues to look out for•Dryer vent material•Gas leaks•Oven CO
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QUESTIONS?
Combustion Safety Basics