J7/J8 PPT'S Flashcards
Category I appliances are equipped with ______ control
draft
If you poke a hole in a category I appliance, what will happen?
Air will go in - flue gases won’t leak out due to the below atmospheric pressure within
Difference between a category I and II appliance and why are cat. II rare?
Category II are considered condensing appliances although they still operate with a non-positive vent pressure (negative)
Category III appliances operate with a _________ vent pressure
positive
Category III appliance venting flue gases will leak out if you poke a hole due to the positive pressure. True or False?
True
Are category III appliances condensing?
NO
Category IV appliances operate with a positive vent static pressure with flue loss not less than __%. It is a ___________ appliance.
17%
condensing
A vent that is too large has what effect?
Mixes too much dilution air with combustion products
Excess air dilutes & cools the gases to a point where ______ can not be created or maintained.
draft
A vent that is too small constricts the flow of gases and does not have the capacity to carry all of the combustion products outdoors. True or False?
True
Purpose of a pressure neutralization device in a fan assisted appliance?
To allow flue gases to be vented by buoyancy
Fan assist appliance regulates _________ air supply but does not affect venting pressure
combustion
Fan assist appliances are more efficient that natural draft appliances. True or False?
True
Do fan assist appliances have flow switches?
Yes, it proves the burner fan is operating
Why are fan assisted appliances more susceptible to condensation?
Produce lower volume and temp than draft hood equipped units
Vent connectors can be made of either ‘c’ or ‘b’ vent type. True or False
True
Main vent can only be of the ‘B’ type. Depending on temperatures. True or False?
True
B vent can not exceed what temperature rating?
470F
What is a major factor in creating draft?
Height
The higher the vent stack, the ________ the pressure and _______ the gas
lower, hotter
Natural draft appliances rely on _______ and ___ to create draft
height and TD
Where to find definition for Damper, Flue Damper, and Vent damper?
B149 code
Newer appliances have fans and are called “________” or “induced” draft venting.
forced
Gas appliances require a flue that has a good draft in it to get rid of products of combustion after most of the heat has been removed. True or False?
True
What is one problem with natural draft appliances? How to correct it?
Draft occurs even when appliances are off.
A vent/flue damper
There are two types of flue dampers, name them
Electric
Thermal
Are electric or thermal flue dampers more common?
Electric
Thermal dampers are maintenance free, do not require power, and operate automatically. True or False?
True
How do thermal dampers open?
Bimetal mechanism that is heat sensitive
Are thermal or electric dampers more reliable?
thermal
No flue damper causes warm air to escape through the appliance. True or False?
True
Flue dampers allow the appliance to hold and radiate remaining heat into the space. True or False?
True
Exhaust fan dampers are normally _______ and must be proven open via a __________ switch to control the flow of flue
closed
proving/end
Dilution air _______ and _____ combustion gases
cools and slows
Draft hoods keep the burner at _________ pressure. Also known as ?
atmospheric
neutralization stack effect
Draft hoods also provide spillage relief in case of a _________ and stops flame roll out
spillage
A fan assist appliance does not develop any venting pressure. It only assists in combustion air supply. Draft still dependant on bouyancy. True or False?
True
Stack effect must consider conditions such as?
Chimney height, TD inside and outside, wind fluctuations
A draft regulator is also known as a ?
barometric damper
A draft regulator/barometric damper is a hinged, weighted door on the _________ of the flue
opening
A barometric damper/draft regulator is typically used on which type of appliances?
Ones that have a negative over-fire draft, such as a fan assisted burner or oil fired burner (can be modulating or on-off)
An appliance with a barometric damper shall have a vent pressure that is?
below atmospheric
Barometric dampers maintain ___________ draft in the appropriate range of the combustion chamber (below atmosphere)
continuous
Neutral over-fire appliances only require a _____ _______ but negative fired appliances require a ________ _________
draft hood
barometric damper
Single acting barometric dampers ___ allow spillage
do not
Double acting barometric dampers ________ spillage
allow
What is the purpose of a double acting draft regulator/barometric damper?
to allow spillage into the mechanical room until the stack warms enough to sustain the draft
Single acting is required on oil fired burners and incinerators. True or False?
True
A draft regulator shall not be used as a substitute for a draft hood. True or False?
True
Most installations are equipped with ______-acting barometric dampers, EXCEPT for?
double acting
incinerators and oil fired burners
Where is a barometric damper installed?
In the flue between the appliance and the chimney
Barometric dampers should, but not always, be installed in the appliance ______ not the _______ ______
vent
common vent
The barometric damper is set for the desired draft conditions using ______ and adjustment screws
weights
If the draft inside the chimney is
_________ than the set-point of the
damper, the damper will ______ and
allow air from the boiler room inside
the chimney, rather than stealing heat from the appliance.
greater
open
Barometric damper weight added affecting draft
- No weight = ______ draft
- Some weight = _______ draft
- Most weight = _______ draft
- fully open, least draft (slow)
- mid open, increase draft (faster)
- closed, high draft (fastest)
What tools can be used to measure draft? (3)
- draft gauge
- magnahelic
- digital manometer if scale is small enough
Normally we measure draft in two locations. What are they?
- over the fire or in combustion chamber
- close to the flue before the damper
Depending on the appliance
manufacturer, it may be critical to
measure the draft in the __________ ________
combustion chamber
If a test port is not available the
draft measurement can often be taken through a ____ port at the burner or on the combustion chamber
site port
The draft setting is set per?
manufacturers documentation
If the draft is too low, _____ some weight to the damper chain (this will choke dilution air and increase the draft
add
If draft is too high, ______ some weight, this will increase dilution air and decrease the draft
remove
Check the draft at the ________ to measure over-fire draft in the __________ chamber. Then you can adjust the damper accordingly
burner
combustion chamber
