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BPI Written Exam - Section 1 Building Science Fundamentals

8. Principles of Combustion: Combustion Analysis, CO

When we refer to combustion, we are talking about gas appliances such as furnace or gas pack heating system, gas water heater, dryer, fireplace, or stove or oven.  All these appliances when natural gas, propane, oil or wood to convert the fossil fuel to usable heat for our homes or appliances.  

A general formula for the combustion process is below, which is just saying that the fuel oil reacts with oxygen to give carbon dioxide, water and heat.

Fuel oil + O2 = CO2 + H2O + heat

An important byproduct of the combustion process is CO (carbon monoxide). CO is odorless and deadly and something BPI takes very seriously.  Their motto is "Do no harm" and they mean it.  During the field exam if you do not turn your ambient CO meter on before you walk into the house... FAIL.  If you do not know how to put the house under worst case conditions to test the CAZ... FAIL.  

CO is formed when there is not enough oxygen delivered to the fuel oil or when the fuel oil and air do not mix well enough, CO will be formed.

If you find high undiltued CO levels above BPI actions levels below are some actions to take to try to fix the high CO levels.  You may ask why even test for CO espically in high efficiency furnaces where little can be changed to fix the problem?  Well the answer is that we are concerned about how the furnace (or appliance) is operating as one piece of a whole system.  The furnace's operation can be influenced by dryers, exhaust fans, AHU and duct leakage and room pressures, so we need to take all those into account.  

Please see the next section to learn more about the actual test that are performed for a combustion analysis.

In an oven

1. Adjust the air intake valve inside the oven (when it cools down) to increase the amount of air intake (its just a lever when a dampener on it)
2. Raise the pedals higher so that more air intake is allowed under the appliance
   
3. If those methods fail, call a service technician

Furnace

1. Inspect the valves and regulators for signs of wear or build-up
2. Check the flame color to see that it is more blue than yellow, a blue  flame indicates a cleaner burn
3. Check the heat exchanger with a mirror to too for cracks in the exchanger
4. Check the flue pipe to make sure nothing is blocking it or clogged in the line
5. If those methods fail, call a service technician
   

Water heater

1. Inspect the valves and regulators for signs of wear or build-up
2. Check the flame color to see that it is more blue than yellow, a blue  flame indicates a cleaner burn
3. Check the flue pipe to make sure nothing is blocking it or clogged in the line
4. If those methods fail, call a service technician

BPI has action levels to take for two types of CO readings.

1. Ambient CO levels (CO levels in the general air of the house) 35 ppm CO is the limit where you should STOP WORK IMMEDIATELY
   
2. Undiluted CO is appliance specific and measured in the throat of the appliance flue

Ambient CO meter that clips onto your belt

A different monitor, allows us to test undiluted CO measurements in the throat of the flue by sticking the metal rod in the hot flue, once the appliance has been on for ten minutes and comes to a steady state.

When BPI says "combustion analysis," we are referring to several tests.  These are important to know and get straight as they are often mixed up by trainees. 

1. Ambient CO levels
2. Draft test
3. Spillage test
4. Undiluted CO test 

 Numbers 2-4 are all done under worst case conditions.  What does worst case actually mean?  Let's go to the next section to find out.

Next Section

1a. Basic terms and definitions

1. Understand airflow in buildings / ducts: CFM, CFM50, CFM25, ACHn, ACH50, FPM
   
2. Understand equipment efficiencies: AFUE, SSE, SEER, EER, HSPF
3. Understand power and energy: watts, BTU/hr, ton of refrigeration  watt-hours, BTU, therm, decatherm
4. Understand effective leakage area
   
5. Understand area weighted R-Value
   
6. Understand baseload / seasonal energy use
7. Understand driving forces (including natural and mechanical: Pressure, temperature, moisture differential
8. Understand behavior of radiation: emissivity, reflectivity, absorbtivity
9. Understand thermal resistance / transmittance: R and U Values; including conversions
10. Understand latent / Sensible heat: evaporation, condensation / specific heat, heat capacity
    
11. Understand total equivalent length
    
12. Understand basics of dehumidification / Humidification as well as measurement equipment
    
13. Understand and convert Pressure units: Inches of Water Column (iwc), Pascal (Pa)
    
14. Understand, identify thermal bridges
    
15. Understand pressure boundary 
    
16. Understand/define stack effect 
    
17. Understand and define exfiltration and infiltration 
    
18. Natural / mechanical ventilation 
    
19. Understand net free area 
    
20. Understand input / output capacity 
    
21. Understand peak electrical demand 
    
22. Understand permeability and perm rating 
    
23. Understand standby loss 
    
24. IAQ (indoor air quality): moisture, CO, dust

1b. Principals of energy, air & moisture

1. Thermodynamics: conduction, convection, radiation, ΔT including air movement due to temperature gradients
   
2. Factors that affect insulation performance: density, installation, moisture
   
3. House pressurization/depressurization by various forces
   
4. Heat gain / loss: internal, solar, heat transmission, air leakage 
   
5. Power and energy: BTU content of fuels, capacity of combustion appliances and electrical appliances 
   
6. Moisture transport mechanisms: bulk water, air leakage, diffusion, capillary action 
   
7. Identify areas of highest relative humidity 
   
8. Principles of combustion: combustion analysis, CO 
   

1c. Combustion science

1. Combustion analysis: oxygen, flue-gas temperature, carbon monoxide 
   
2. Carbon Monoxide (CO) testing of combustion appliances 
   
3. Basics of: Combustion appliance venting, draft, and combustion air including identification of proper sizing/vent tables 
   
4. Understand combustion safety issues: Combustion air, draft, worst case / baseline depressurization, spillage, backdrafting, unvented combustion appliances