duct takeoffs Flashcards
Duct takeoff is required when you want to split the main trunk to move a large volume of air to another zone of the building ,it replaces the
“Y” branch
The duct take off needs to be larger at the cross section where its attached to the main duct for
easy air flow
Two types of duct take offs are
,flat wrapper and curved wrapper
- Flat wrapper is easier to develop then the curved wrapper
true
Flat wrappers are recommended to have a
45 or 1/4 width of the duct going upstream ,this gives about 25 % of a opening
- Curved duct dose not have specific cross section because the air flow has a smoother flow
true
Pto is the take off that”s installed on the plenium and is
50% bigger on the cheeks
- Two types of take offs are flat and a rise takeoff ,4 inch rise is common in residential it helps for air flow to the main duct
true
Furnace installations require a “1 inch clearance from combustibles
( floor joist)
- Parallel top take off cheek can have the same opening as the duct opening , the lenght should equal or greater then the width of the cheek
true
When notching is being done to the Pittsburgh lock , the notches go to
the net line
- Plenium take off is different as to others because it comes off the main plenium with a hammerlock and increases in size at the cross section
true
- Couple things to determine is to make sure the width of the plenium and the pto will fit on it using a simple layout to develope it
true
If the duct is bigger then the plenium you will need to use
triangulation developement
When attaching duct connections reduce 1/2 to the net for
the slip and drive connection
- To develope the top take off draw a base line and a perpendicular line and then the length , now you can mark the opening with 1.5 added on the pto side of rising pto
true
Wrappers are measured by Pythagorean theorem ,to determine this you will do lenght of the plenium opening by squared and the offset of the riser by squared ,add them and then square that number and round to lowest fraction
true
Clinchlock is also known as a
hammerlock
- Hammer lock on straight and sweep uses the transition lock with notches with perpendicular notches to the net line and 30 angle on the ends
true
- Notching of a rising pto is the same as the sweep take off
true
You use a duct connection when ?
No “Y” branch , unsure of location , adding to branch run , change of sides is needed in both directions
Duct takeoff has to be built with curved and heel true or false
false
Whats the size of the plenium takeoff connection at the cross section area ?
150% greater
A flat top take is not used often because ?
It cannot get close enough to the joist
Wrapper lengths can only be done by adding
False
Hammer lock on a break with inside facing up ?
DN UP DN
