Venting Flashcards
What is the minimum effective vent height for a typical venting system?
5’ minimum
Effective vent height is measured from the top of the draft hood to the bottom of the rain cap.
What is the clearance to combustibles for B vent?
1”
C vent has a clearance of 6”.
What type of vent is always used for a common vent?
B vent
What type of draft is produced by temperature differences?
Natural draft
What are the two types of mechanical drafts?
- Forced-mechanical
- Induced-mechanical
Where is the fan located in a forced-mechanical draft?
Upstream from the combustion zone
Where is the fan located in an induced-mechanical draft?
Downstream from the combustion zone
What do natural draft appliances have that allows for dilution air?
Draft control devices
True or False: Draft hoods can be altered after manufacturing.
False
Draft hoods are fitted from the manufacturer and cannot be altered in any way.
Fill in the blank: The effective vent height is taken from the top of the _______ to the bottom of the rain cap.
draft hood
What is the clearance to combustibles for a C vent?
6”
What is the pressure classification for Category III appliances?
Positive
What is the pressure classification for Category I appliances?
Non-Positive
What type of vent is typically used for non-condensing appliances?
B-Vent
What is the primary function of draft control devices?
Neutralize the effect of stack action and dilute the products of combustion
Minimizes the possibility of condensation
What does a draft control device prevent from entering the combustion chamber?
Backdraft
Prevents production of carbon monoxide and soot or carbon
What is the role of draft control devices when appliances are not firing?
Assists in room ventilation
Helps maintain air quality and safety
What are the two types of barometric draft control?
Single acting and double acting
Rely on pressure within the venting draft control
What is the operation of a double acting damper?
Swings inwards to allow dilution air and outwards to allow products of combustion
Used on gas fueled appliances
What material is typically used for vent connectors?
Galvanized or aluminum
Generally of single wall construction (C vent, minimum 26 gauge)
What must be used to connect the vent connector to the common vent?
Certified double wall to single wall adapter
Ensures safe and effective venting
Fill in the blank: The vent connector and common vent must be the same size for _______.
Venting a single appliance
Ensures proper flow of combustion products
What is the minimum rise recommended per foot for vent connections?
½” per foot
This is a guideline for proper venting.
Where should the change in size of the vent connector occur if it is larger than the draft hood?
At the flue collar or draft hood outlet
If the appliance has an internal draft hood, change should be made at the outlet of the appliance.
Is a single wall vent connector (Type C) permitted to pass through a floor or ceiling?
No
Unless the combustible material is guarded or a ventilated metal thimble is used.
What must not be used to fasten a moisture exhaust duct from a clothes dryer?
Screws
Only approved tape can be used.
What is the most common shape for vents and why?
Round, as it has the least restriction to flow
This shape is preferred for efficiency.
How high must vents extend above a flat roof?
A minimum of 2’
They must also be 2’ higher than any portion of a building within 10’.
What is the minimum height for vents with positive vent pressure above obstructions?
18” higher than any obstruction
This ensures proper venting without interference.
What is the minimum extension requirement for chimneys above the roof?
A minimum of 3’ and 2’ higher than any portion of a building within 10’
This is vital for effective venting.
What type of appliances can be vented into B vent?
Only Category I appliances
This specification is important for safety and efficiency.
What is the clearance to combustibles for Type B vent?
1” clearance
Type B vent is used on gas burning appliances with draft hoods.
What materials make up the construction of Type B vent?
Aluminum inner lining and galvalume outer wall
Between the walls is dead air space used as insulation.
