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CAZ P R E S S U R E
T E S T I N G
Presented by Rich MooreInvisible EnergyDenver, CO
[email protected] 31, 2011
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Goals of this session
Some Combustion and Equipment Basics
Recognize the need for combustion safety testing on gas
fired equipment
Test In/Test Out
Recognize the interaction and impact of various features
of the home on combustion equipment
Learn how and where to test for CO, draft spillage, and
CAZ pressure
Be familiar with some testing protocols and equipment
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Introduction
Who are you?
HERS Raters?Weatherization Technicians?
Home Performance Contractors?
Home Improvement Contractors? BPI Certifications?
Is anyone doing combustion safety testing?
What protocol?Why do you feel the need for this testing?
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Finish this sentence
The house is a
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Systems Thinking-Before
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Systems Thinking-After
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Combustion-How It Works
Combustion of any fuel (natural gas, propane)
requires three things:
Fuel
Air
Ignition Source
Equals
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Fuel-Natural Gas
Composed mainly of methane (81%)
Lighter than air (specific gravity .65)
BTU content/cu.ft. =700 to 1200
Ignition temperature of 1100 to 1200F
Typical manifold pressure = 3.5 WC
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Propane
Composed mainly of propane (95%)
Heavier than air (specific gravity 1.53)
BTU content/cu.ft. =2500 to 2700
Ignition temperature of 920 to 1020F
Typical Manifold pressure = 11 WC
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Heating Oil
Grade Heating Value(Btu/ gal) Fuel Oil No. 2 137,000 - 141,800 Residential Heating
Fuel Oil No. 6 151,300 - 155,900
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Air
Combustion Air
Primary
Secondary
Dilution
Excess
Natural gas appliances needs ~10 cubic feet of air for
combustion for every 1 cubic foot of fuel.
Propane appliances needs ~25 cubic feet of air for
combustion for every 1 cubic foot of fuel.
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Combustion Air Guidelines
Uniform Mechanical Code Chapter 7:
Two openings, with each opening having one square
inch/4000 btu
Other variations on this, depending on jurisdiction (local
codes), equipment type and location.
Some jurisdictions allow for combustion air from
the volume of the home, a combination of volumeand exterior, or only from the exterior.
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How much air is needed for combustion?
Assuming 1000 btu/cubic foot of gas, then:
A 100,000 btu furnace requires 1000 cubic feet of
air for every hour it burns.
(100,000 btu = 100 cubic feet of gas x 10 cubic feet
of combustion air/ft3 = 1000 cubic feet of air)
Where is this air coming from? How is combustion
air allowed to the appliances?
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Ignition Sources
Standing Pilots Electronic
Spark Ignitors
Hot Surface Ignitors
Others
Matches,candlesmanualignition!
(Not a good idea!)
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Open & Closed Combustion Appliances
Open Combustion:
An appliance that gets its combustion air from the same area as
the unit is located
(you could reach in and touch the flame)
Closed Combustion: (aka Sealed Combustion)
An appliance that gets its combustion air from the outdoors,
piped directly to the units burner area (the combustion
chamber is completely sealed and isolated from the zone it is
located in)
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Drafting / Venting
Since all combustion appliances create combustion
byproducts, they must be removed to the outside via aventing system (masonry chimney, single or double
wall metal pipe, or plastic vent, etc.).
Drafting: (Negative pressure) A current of warm exhaust gasses. This
effect creates a slight negative pressure, carrying the gasses out
of the home via a chimney or vent stack.
Positive pressure venting involves the use of a fan to push
exhaust products out of the home.
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Drafting
Most residentialfurnaces are eitherCategory I(standard or mid-efficiency) orCategory IV (highefficiency).
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Four Factors for Good Drafting
Delta T = Delta P
The greater the temperature difference, the greater the pressuredifference (draft)
Vent Height
The greater stack height, the greater the draft Friction
Venting design & installation
Air Flow Is there enough (combustion or make-up) air? If air is removed
during the combustion process, is there a supply of air toreplace it?
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Open Combustion Appliances
These are both open combustion appliances. Air for
combustion is drawn from the same area (zone) as the
appliance. It is often house air.
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Category I Furnaces
Each of these furnaces,though different
AFUEs, are Category I
appliances.(The left unit is
~ 65%, the right is80%. Each has negative
pressure venting, non-condensing)
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Open or Closed? High Efficiency?
This is a Category Iopen com bustion
furnace.The combustion air
source is house air, asfor the hot water tanknext to it.
AFUE = 80%
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Category IV Furnaces
This 90+ AFUE(condensing)is a Category IV, with apositive pressure ventsystem.
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Closed Combustion Appliance
Both the hot waterheater and furnaceshown here are closedcombustion appliances.They each drawcombustion air fromoutdoors, not the house
volume.
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Closed Combustion Appliance
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So what? (moving on)
If code is met, will the appliance work properly?
If a new home has a CO, is everything OK?
If the air changes are above .35 NACH, is there enough air
for combustion?
Can I tighten a house below .35 and have enough air for
combustion? If there is sufficient ventilation per ASHRAE, can it
interfere with combustion?
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Air Sealing
Taking a House As A System look, what
are some typical improvements made toreduce air leakage in the home?
Attics-top plates, open walls, drop ceilings,
plumbing and electrical penetrations, etc.Wall insulation (dense pack)
Basements
Rim joists. Wall penetrations, windows, etc.
Ductwork
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Pressure Problems
Know the impact of your air sealing work on
combustion appliances:
Over-tightening or under-ventilating a home
Exhaust appliances
fans, dryers, fireplacesDuct Leakage
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Pressure Problems
A home may not have had a pressure problem
beforeyou began improvements.
The effects of tightening a home may create
adverse conditions afterwards. (Backdrafting,
pressure imbalances, etc.)
Dont assume anything. Test in, test out.
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Ductwork
The impact of leakyductwork can never be
emphasized enough.
Sealing only supplyductwork can lead to
catastrophic results,including backdrafting inthe CAZ, or excessive
positive pressure in thecore of the home.
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Effect of Duct Leakage On Open
Combustion Appliances The leaky cold air return on
this furnace can draw
combustion products down the
flue and into the ductwork, for
delivery into the living space.
In addition, it robs the
appliances of necessary
combustion air, possibly
leading to CO production.
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Combustion Appliance Zone Pressures
Combustion
appliance zone (CAZ)pressures can easilyovercome the draftpressure required tosafely exhaust hot
water tanks andfurnaces.Typical draftpressures may be-5 pa or less.
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House to Garage Connections
If air sealing isperformedthroughout the home,
makeup air forappliances may nowonly be available via thehouse-garage connection.Be careful!
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Please Note
IN NO CASE SHOULD ANY HOME
IMPROVEMENTS BE MADE IF THERE ARE
UNVENTED APPLANCES IN THE HOME.
THIS INCLUDES FREE STANDING SPACE
HEATERS AND COOKING APPLIANCES*.
*Gas fired cooking appliances should have exhaust fansinstalled as an upgrade
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Carbon Monoxide
An odorless, colorless, tasteless toxic gas that can be
lethal at high concentrations.
Low level poisoning contributes to health problems.
Has distinct odor when combined with byproducts of
incomplete combustion.
Is caused byincomplete combustion
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Carbon Monoxide
Other byproducts of combustion can be harmful or
damaging to the occupants and dwelling, including:
Carbon Dioxide (CO2)
Moisture
Oxides of Nitrogen (NOx)
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This is the BPI protocol for CAZ
Testing. Other protocols may
be used in other programs.
BPI certified contractors should
adhere to BPI auditing
standards as well.
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Testing Overview (before the CAZ setup and test)
Check all accessible fuel lines for leaks
Check the venting systems to see that they are safeand intact.
Be sure the vent is cool to the touch
Hand check venting integrity
Check for carbon in the heat exchanger, draft hoodand gas vent(s) of all appliances being tested.
Another hand check
Visually check for cracks in the heat exchanger.
Drill test holes in the gas vent(s) of atmosphericdrafting appliances.
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Combustion Safety Testing (CAZ)
Testing is performed to determine the CAZ (CombustionAppliance Zone) pressure
This test ultimately determines thepoten tial (not the reality) of anappliance backdrafting exhaust gasses into the home.
Measurements of CO, draft , spillage
Other items that can or should be tested:
Cracked heat exchanger
Gas leaks
High limit operation Pilot safety controls
Combustion Efficiency
Stack Temp, O2, excess Air
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CAZ.HELP!!!
Some ideas to help CAZ and Mechanical testing
go smoothly Do this test first.
If you find that there are serious mechanical system or CAZproblems, you may not be able to/need to proceed with further
home testing.
Determining Worst Case can be tricky. While doingyour client interview and house walkthrough, close and
lock all exterior windows and doors. Open all interiordoors. Start setting up the test as you take notes on thehome, while listening to the homeowner (thatsrightmulti-task)
C b ti S f t T t P d f V t d
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Combustion Safety Test Procedure for Vented
Appliances
1. M e a su r e th e Ba s e P r e s su r e .
Start with all exterior doors and windows closed and thefireplace damper closed. Set all combustion appliances to the
pilot setting or turn off the service disconnect. Combustion
appliances include: boiler, furnace, space-heaters, and water
heater. With the home in this configuration, measure and
record the baseline pressure of the mechanical room WRT
outside.
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CAZ Testing
Measuring Baseline
Find an easy spot to run a reference tube to the outdoors
from the CAZ.
If the Blower Door is set up, can you run a long tube to
the exterior from the CAZ?Rim joist penetrations (Line Set, Gas line, electrical
penetrations, etc.)
Under the sill plate?Use a window and tape over the remaining gap.
Use time averaging feature if windy conditions exist.
Combustion Safety Test Procedure for Vented
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Combustion Safety Test Procedure for VentedAppliances
2. E s ta b lis h t h e W o r s t Ca s e .
Turn on the dryer and all exhaust fans. Close all interior doorsthat make the CAZ pressure more negative. Turn on the air
handler, if present, and leave (it) on if the pressure in the CAZ
becomes more negative, then recheck the door positions.
Measure the net change in pressure from the CAZ to outside,
correcting for the base pressure. Record the worst case
depressurization and compare to the CAZ Depressurization
Limit Table.
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CAZ Dep r essu r iza t ion Lim it s
Orphan natural draft water heater (including outside chimneys) -2 pa
Natural draft boiler or furnace commonly vented with waterheater
-3 pa
Individual natural draft boiler or furnace -5 pa
Induced draft boiler or furnace commonly vented with waterheater
-5 pa
Power vented, induced draft boiler, furnace alone or fan assistedDHW alone
-15 pa
Chimney-top draft inducer; exhaust type or equivalent; high staticpressure flame retention head oil burner; direct ventedappliances; sealed combustion appliances
-50 pa
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CAZ Testing
Turn on regular fans and dryer first, then proceed with air
handler. The air handler must be run at the highestspeed used.
If possible, observe CAZ change with each fan.
Gourmet Cooktop Exhaust? Add separately.
DryerDont forget to clean lint filter.
Fireplace? Is air handlers filter clean?
Cooling present? Run cooling from thermostat, with outdoor
unit off. (You are only concerned about air pressure, not
temperatures.)
No cooling? Run air handler with fan control (summer switch),
or you may have to run heating.
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CAZ Testing
Positioning interior doors-use smoke. Rooms that are
positively pressurized should have doors closed.Negatively pressurized rooms should have doors open.
A good rule of thumb is: If the smoke comes toward you, the doorcomes toward you. If the smoke goes away from you, the door goesaway from you. (Note this only applies to bedroom or otherdoors that open in to the room, away from the CAZ.)
Worst case CAZ pressure is the strongest negativepressure in the appliance zone, of whatever configuration
the fans/doors, etc. minus the baseline (stack effect).
Combustion Safety Test Procedure for Vented
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Combustion Safety Test Procedure for VentedAppliances
3. Mea su r e W or s t Ca se Sp i lla ge , Dr a ft , CO.
Fire the appliance with the smallest Btu capacity first, test for
spillage at the draft diverter with a mirror or smoke test, and
test for the CO at the flue at steady-state (if steady state is not
achieved within 10 minutes, take the CO readings at the10
minute mark). If the spillage test fails under worst case, go toStep 4. If spillage ends within 1 minute, test the draft in the
connector 1 - 2 after the diverter or first elbow.
Fire all other connected appliances simultaneously and test
the draft diverter of each appliance for spillage. Test for CO inall appliances before the draft diverter.
Combustion Safety Test Procedure for Vented
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Combustion Safety Test Procedure for VentedAppliances
4. Mea su r e Sp illa ge , Dr a ft , CO u n d e rn a tu r a l con d it ion s ( if sp illa ge fa ils u n d e r
w o r s t ca s e ) .
If spillage fails under worst case, turn off the appliance,the exhaust fans, open the interior doors and allow the
vent to cool before re-testing. Test for CO, spillage, anddraft under natural conditions. Measure the netchange in pressure from worst case to natural in the CAZto confirm the worst case depressurization taken inStep 2 outside. Repeat the process for each appliance,allowing the vent to cool between tests.
Combustion Safety Test Procedure for Vented
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yAppliances
5. Am bien t CO.
Always monitor the ambient CO in the breathing zone during
the test procedure and abort the test if ambient CO goes over
35 ppm. Turn off the appliance, ventilate the space, and
evacuate the building.
The appliance must be repaired and the problem correctedprior to completing the combustion safety diagnostics.
If the ambient levels exceed 35 ppm during testing under
natural conditions, disable the appliance and instruct the
homeowner to have the appliance repaired prior to operating
it again.
h
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Other Notes
Newer two-stage and variable input equipmentshould be tested at various firing levels to ensure safe
operation.
Consult with the equipment manufacturer as to howthe unit can easily attain high-fire and high fan speed
(for optimum depressurization). Remember, the object here is to try and force the
combustion appliances perform poorly (backdraft,
create CO, etc.). It may necessitate setting the houseup a bit differently than the protocols tell you. (i.e.
what if there are two air handlers?)
Test Equipment
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Test Equipment
Fi V ti P bl
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Fix Venting Problems
This is from a new home!
Combustion spillage
Brother-in-lawinstallation
Learn to observe!
Whats wrong with these pictures?
R b
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Remember
Houses with central returns vs. returns in everyroom may quite likely change your door arrangement
when the air handler is operating.
Leaky ductwork can cause a zone to go positive,negative, or remain neutral.
If there is an operable and usedfireplace, it may benecessary to run a blower door at a low (~200 to 400cfm or higher) flow in order to simulate its drafting.
T t L ti 6 % F
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Test Locations-65% Furnaces
The vent on thisfurnace should bedrilled approximately18 from the top ofthe draft hood. Thishole is for testing
only the draft, notCO.
Drill and test here
Test Locations 80% Furnaces
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Test Locations-80% Furnaces
The test hole on this furnace should bein the adaptor section above the
combustion blower. Avoid drilling intodouble wall vent. This test hole is formeasuring draft and CO.Spillage tests are not usually taken on
furnaces like this. (They do not have adraft hood, but a test can be done at theburner area.)
Drill and test here
Test Locations 90+ Furnaces
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Test Locations-90+ Furnaces
It is preferred that PVCventing not be drilled.
Always try to test at the venttermination. Somemanufacturers will allowdrilling of the vent pipe,however it must be
completely sealed aftertesting is done, withapproved material.
CO only is measured on 90+
furnaces (positive pressureventing).
T t L ti CO t ti f 6 % F
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Test Locations-CO testing of 65% Furnaces
The top picture shows thecorrect location for COmeasurement on a 65%efficiency unit. Do notmeasure CO in the ventpipe when a draft hood is
present. One CO reading is taken
at every port under thedraft hood; one for each
burner. The numbers arenotaveraged.
This
Not this
Test Locations-Spillage
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Test Locations-Spillage
On a draft hood furnace,
spillage is tested usingsmoke, matches, or amirror, to check for thepresence of combustion
products. If spillage is present, the CO2will extinguish a flame.
A mirror will fog over fromthe moisture content of the
gasses.
Test Locations Hot Water Tanks
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Test Locations Hot Water Tanks
An atmospheric water heater is
tested for spillage around thebase of the draft hood, againusing smoke, matches or amirror.
CO is measured inside thedraft hood, underneath it,before dilution air enters. Thereare two readings taken, one
from each side of the baffle.
CAZ Testing
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CAZ Testing
(Optional) While running furnace in the Heat mode,install thermometers to measure heat rise at 5 minutes.
Supply air minus return air.
While running furnace (whatever speed), use smoke to findduct leaks. (Youve got ~ 5 minutes to get the equipment toSteady State!)
Listen for air flow noises, duct popping, or whistling. Theseare signs of leakage, excessive pressures, or other ductproblems.
At steady state, measure the CO, draft & spillage.
Ap p lia n ce s m u s t r e m a in ign it e d fo r t h e e n t i r e t e s t !
Ovens & Cooktops
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Ovens & Cooktops
Oven CO levels are
tested at the outletport, usually located atthe top/back of theunit. Testing is done
after 15 minutes ofoperation, and levelsshould not exceed 800
ppm air free.
Stove courtesy of Warp 8 Model courtesy of Compass Records
How Much CO Can There Be?
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How Much CO Can There Be?
The BPI Standards list acceptable levels of CO.
Some Manufacturers provide a CO level that theirequipment must be operating at.
For example: The CO levels at the exhaust breachshould be 105-110 ppm on high fire on all units.(Munchkin Boilers)
Finally
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Finally
Dont get in over your head!
Know what you are doing. Get hands-on training. If you are lost, ask for help. (Its OK to ask for help.)
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I N V I S I B L E E N E R G Y / R I C H M O O R E
D E N V E R , C O
R G A L E N M O O R E 1 @ M S N . C O M
3 0 3 - 9 1 9 - 9 8 4 9
THANK YOU