Comercial Hvac Drawings Flashcards
What are some advantages of continuous blower operation ?
Improved air quality
Increased comfort
Reduced temp variations
What else does continuous blower operation prevent ?
Stratification
What is stratification ?
When cool dense air sinks while warm and thin air rises
What is the dweyer air meter ?
Air velocity and static pressure indicator based on variable flowmeter principles
What is the pilot tube ?
Has 2 tubes the inner one being for total pressure and the outer one for static pressure.
Has 8 small holes measuring 0.04 inches to measure the static pressure
What is a manometer ?
Measures air pressure
Bourdon tube type cannot be used to measure small pressures
There is also I tube manometers that are made of glass. Graduated in inches and filled with liquid. One end of the tube is open to the atmosphere while the other is connected to a pitot tube and placed in the duct. If the pressure of the air inside the duct is slightly greater than the surrounding atmospheric pressure the water colloum will be depressed and force the other one up. inclined manometers are basically a u tube manometer
Which manometer is the most accurate ?
Digital manometer
A pressure of one psi will support what ?
A colum of water 2.31 feet or 27.72 inches high
What is a magnetic gauge ?
A vacuum gauge that uses a precision diaphragm to measure pressure differences
What is a velometer ?
An airflow meter that takes readings in fpm or meter per second
Used for takeing direct readings of air velocities
Not designed for gas mixtures other than air and not intended for use where static pressure exceeds 250 degrees Fahrenheit or 10” wc
What is are the two anemometer ?
Thermal
Roaring vane
What does an anemometer measure ?
Air velocity
Air volume
Air temp
How does the thermal anemometer work ?
Measures air velocities by heat transfers from a small wire immersed in the air
What is a balometer?
Referred to as air capture hoods are factory Caliburated for readings between 0cfm and 2000cfm
Reads velocity
What is a barometer used for ?
Measure atmospheric pressure
What is atmospheric pressure?
14.7 psia
What is the standard air conditions?
Air density of 0.075lb per cubic foot which corresponds to dry air at 70 degrees Fahrenheit. Barometric pressure of 29.92
How is the pitot tube placed in the duct
So air flows into it
With a pitot tube how are pressures measured v
Velocity can not truly be measured it is found by subtracting the static pressure from the total pressure.
Total pressure tube comes off too
Static pressure tube comes of the side in the middle
What is dynamic pressure loss ?
Happens when a change in velocity or direction occurs
What is the aspect ratio of straight duct ?
Max 4:1
It is always equal to the long side divided by the short side
What type of duct has the least friction loss ?
Round has the least then share then flat oval
As the aspect ratio increases so does friction loss
What is the best possible aspect ratio for an elbow ?
1:1
What is center line radius ?
The distance from the throat radius to the center of the cheek
What is radius ratio ?
The relationship between the centerline radius and the width of cheek. A radius ratio of 1.5 is the best also known as full throat while a radius ratio of 1 can be used in residential
What is the purpose of splitters in an elbow?
Reduces dynamic pressure loss
What are splitters ?
Installed in an elbow to
Improve the radius ratio
What is static regain?
The process of converting velocity pressure to static pressure
What is the converging angle for static regain?
30 degrees
What is the diverging angle of static regain ?
20 degrees
How is pressure velocity found ?
Velocity divided by 4005 squared
What is a long way elbow ?
Wider than it is deep
What is a short way elbow ?
Deeper than it is wide
Does more gores on an elbow mean the more efficient the elbow is ?
Yes
When are splitters used ?
When there is no possible way of using a full throat elbow
How are turning vanes spaced ?
With aspect ratio of 5:1 they are produced in 2 sizes
Type b for elbows up to 18” in width
Type d for elbows over 18”in width
What are 2 types of turning vanes ?
Single thickness
Double thickness (tubular)
When an eccentric (off center) taper is used in either a diverging or converging the side of the taper should be what angle ?
30 degrees
When using a concentric taper the sides of diverging angle should be what as well with converging ?
Diverging = 45
Converging 60
When
Makeing transitions for connecting to equipment what should the angles be for diverging and converging ?
30 for diverging
45 for converging
When are 2 peice stream lines used ?
In areas where ductwork cannot be made to offset around an obstruction that would exceed 20% of the cross section area of the duct
When diverging angles cannot exceed 20 degrees while converging angles cannot exceed 30 degrees and be no less that 1.25 times the width of the duct that it’s attached to is called what?
Non symmetrical streamliners
What grade of boots should be used to secure fan mounting angles to isolation bases ?
Grade 5 or better
What are the 6 diffrent types of bases mounts and hangars ?
Interia bases
Isolation bases
Isolation mounts
Motor slide bases
Isolation options
Isolation hangers
How can you isolate noise caused by fans ?
Mounting fans on spring isolators
Hanging fans on isolation hangers
Using concrete filled interia bases installed on rubber mounts and cork pads
What are the 4 type of isolation mounts ?
Isolation rails
Isolation bases
Interia bases
Rooftop isolation rails
How are isolation rails supplied and designed ?
Designed to run the full length of the supported equitment. Small fans may require the use of rails which are used in conjunction with rubber in shear or spring ceiling isolators
How are isolation bases used ?
Run the full length of the equitment they support and include the fan motor
For isolation bases you may use rubber in sheer , floor mount , spring floor or housed floor isolators
Where additional mass is required what should be used ?
Use an Interia base to dampen and dissipate vibrations on large or high velocity equitment. The extra weight allows u to use stiffer springs which limits movement. The base is designed as a mild for concrete
Where are rooftop isolation rails used ?
To provide vibration isolation for roof exhaust fans and roof top units
When mounting the motor to the inertia base what is required ?
A seperate motor slide base
What are 5 types of isolators ?
Free standing
Restrained spring
Housed spring
Rubber in shear
Neoprene mounts
Where additional lateral support is needed what kind of isolators should be used ?
Housed spring isolators
How are springs identified ?
Color coded
What are free standing isolators ?
They are unhoused isolators
What is the typical source of vibration ?
Machinery
How do isolation systems work ?
Block the sound path as it travels to the sound receiver
What is the minimum number of hangers for each fan coil unit ?
4
Where are flexiabke duct connectors used ?
Between machinery and the duct work
How are flexiabke duct connectors rated ?
To be airtight and water proof for up to 10”wc or negative 10” wc
What are flexiabke duct connectors made of ?
PVC or neoprene fabric coat
To convert sound energy into heat what is used ?
Porous materials of varying density and composition
When evaluating materials for Thier ability to absorb sound what do you use ?
Absorption coefficient
What are 3 types of silencers ?
Reactive
Absorptive
Combination of the two
What are reactive silencers ?
Provide better noise attenuation at lower frequencies while absorptive silencers can achive much greater noise decrease at higher frequencies. The best is the mixture of both of them
What are 2 ways to control duct line noise ?
K-27duct
Acoustical lining
What is k-27duct?
Used for high pressure
External pressure tight metal shell a layer of fibreglass insulation and an internal perforated liner controls fan noise cross talk
Should duct liners be used on exhaust systems ?
No or anything conveying solids
What must be done when velocity exceeds 4000fpm
Metal nosing must be installed
What type of fasteners are used for duct liners
Adhesively secured fasteners
Mechanically secured fasteners
Welded secured fasteners
What are micro air ducts ?
Designed to provide air duct thermal insulation. Noise absorption. And Vapor barrier all in one product
What are sound absorbers ?
Another form of sound attenuation in air handling system. A 3 foot silencer provides the same amount of noise control as 250 feet of liner duct will
How are sound absorbers tested ?
Tested with both forward and reverse airflow
Should a sound absorber be located directly after a duct elbow or divided flow fitting ?
No
What is the transmission of noise through the ductwork into the living room know as ?
Breakout noise
What is breakin noise ?
Sound that gets into the duct from surrounding areas and transmits before breaking out also know as crosstalk’s
Is rectangular or round duct more effective acoustically?
Round is less effective as it tends to be more rigid and absorbs less sound
What 3 types of lining can be used on ducts ?
Fiberglas board
Internal liners
Duct wrap products
What type of filters provide the best performance?
HEPA
What size of particle is naked to the human eye ?
0.01 to 5
What 5 techniques are used to capture contaminants?
Straining
Interception
Impingement
Impaction
Diffusion
What is straining ?
Predominate method used to remove particles in low efficiency air filters
What is inertial impingement ?
Occurs when a large density particles collide with the fibers and attach to the media
Adhesive or oily tacklers can be added as well to enhance efficiency
What is impingement?
Predominant method used in flat panel filters.
What is interception?
Predominant method used in medium efficiency air filters
Bags and extended surface final filters
What is interception?
Predominant method used in medium efficiency air filters
Bags and extended surface final filters
How does diffusion work ?
Predominant method used on hepa filters
What are electronic air cleaners ?
2 stage precipitators
What are 2 types of air washers ?
Spray type
Cell type
What is a spray type washer ?
Consists of a chamber for a spray nozzle bank. A tank for collecting water and an eliminator section
How are air washers designed ?
For the suction side of the fan only
Are cell type air washers more efficient than spray type?
Yes they remove 70-90% by weight of airborne particles
If the air is cleaned with an air washer what can be used to keep relative humidity down ?
Drift eliminators work on the principle of impingement
What are 2 methods of efficiency testing for filters ?
Dust spot and weight test
How do dry media filters work ?
Increase in efficiency as they collect materials
What must each commercial individual filter section contain ?
Magnahelic gauge
What do viscous impingement filters do ?
A hive weight efficiency of up to 70%
What are permanent aluminum filters used for ?
To protect the heat transfers coils suited for installations where moisture is high and corrosion conditions are there
What is the efficiency percentage of a medium efficiency filter ?
Almost 95%
What is used for testing high efficiency filters?
Only the dust spot test and must have efficiency of greater than 40%
When are dry media filters most efficient ?
At low air filtration velocity
MERV ratings are based on what ?
Ashare 52.2
What type of info are design professionals required to include?
Use of turning vanes or splitters
Location of access doors
Location and type of balancing dampers
Location and type of diffuser
Requirements for duct installs
Location and type of fire dampers
Details of offsets required
Where no specs are set by the designer what pressure of wc should we resort to ?
1”WC for
2”WC roe duct work upstream of vav boxes
What are the classifications of velocity ?
Low pressure = 1/2” to 2” wc
Medium =3”-6” wc
High =10”
What 8 criteria should be considered when assembling a duct system ?
Dimensional stability
Thermal conductivity
Seismic restraint
Leakage control
Vibration
Noise
Exposure to damage
Support
What are the pressure classifications for ductwork ?
STD indicates standard air duct construction regardless of velocity
STV indicates standard construction for variable volume ducts
A indicates the other pressure classes
What are the 7 duct pressure classes ?
1/2” 1” 2” =low
3” 4” 6” =medium
10” =high
How much should aluminum duct be thicker than galvanized duct ?
44% thicker
What are residential duct system classed as ?
As low pressure 1/2” wc and lower velocity’s of less than 1000 fpm in the main trunk
What characteristics need to be considered for industrial duct ?
Abrassivness
Concentration
Corrosiveness
What materials can be used for duct work ?
Copper
Aluminum
Galvanized
Stainless
Finerglass
As buildings get tighter what happens ?
The demand for fresh air increases
When selecting a transverse joint what must be considered ?
Pressure class
Sealing requirements
Materials involved
Duct support intervals
On spiral what should be done when sealing ?
Apply a coat to make end of coupler prior to joining then brush sealer over all joints screws and flanges
What are the seal classes ?
A is 4” wc and up everything must be sealed
B is 3”wc all transverse joints and longitude seams must be sealed
C is 2” wc just transverse joints must be sealed
What percent of volatile solvents can be in liquid sealants ?
30-60% and therefore they may shrink
What do some mastics have embedded in them ?
Fabric
What is the shelf life of sealants ?
Less than 6 months
What are screw miniumims ?
Minimum 3 screws for up to 14” must be placed at 15” intervals of circumference
Minimum 4 for over 14”
What are screw miniumims ?
Minimum 3 screws for up to 14” must be placed at 15” intervals of circumference
Minimum 4 for over 14”
What is the best seam for round ?
Butt welds
On a beaded sleeve joint what is the insertion depth of it ?
2” minimum lap
When is a companion flange used ?
On duct over 60” in diameter
What are the most common round duct reinforcements?
Angle rings
What 3 company’s make up the hanger system ?
Upper attachment
Hanger itself
Lower attachment
What is normal duct hangar spacing unless specified?
8-10 feet
Whst may wider ducts require for hangers?
Use of trapeze bar
When joint is crimped what is the minimum insertion ?
1”
What are the 2 fan classification groups ?
Axial and centrifugal fans
How can we identify axial fans ?
K-wheel is blade cannot be adjusted
A-wheel is blades can be adjusted only when fan is not operating
C-wheel is blades can be adjusted while operating
What are 3 types of axial fans ?
Propeller fans
Tubeaxial fans
Vaneacial fans
What is the propeller fan ?
Most common fan found in resi commercial and industrial
Run at slower rpm and moderate temps
Can handle large volumes of air at low static pressure
Usually no duct attached to them
What is a tube axial fan ?
May be considered heavy duty propeller fans and are arranged for duct connections
All axial fans discharge air in spiral motion which produces high duct system losses due to excessive turbulence
Enabling operation of pressures and efficiency’s up to 65%
What is a Vaneaxial fan ?
Most efficient has guide vanes added to help improve airflow
What are centrifugal fans also know as ?
Squirrel cage
What diffrent types of blades can be on a centrifugal fan?
Airfoil blades
Backward curved
Backward inclined
Radial tip
Forward curved
Radial blades
When would u use forward curved blades ?
Low pressure hvac systems common wheel diameters up to 24”
When do we use airfoil blades ?
Used where clean air energy savings it’s important self cleaning and reinfinement of flat blades backward inclined fan
Most efficient of all types !!!!
What are backward incllime blades used for ?
Used in Large hvac systems has disadvantages because you need larger shaft and bearings
Used in resturant exhaust systems
Where are radial blades used ?
Used for transporting wood chips and grain systems
What are some additional fan classes ?
Mixed flow
Roof ventilators
Cross flow blowers
How are motor positions shown and determined ?
Facing the drive side which is opposite of the inlet fan. Letters wxyz show the motor location in relation to drive shaft
If an elbow is placed near a fan outlet what should be the minimum ratio?
1.5 and should be arranged to give the most uniform flow
How can complete recovery of airflow be achieved if an elbow is placed near a fan outlet?
The effective duct length is 2.5 diameters or more
Die’s discharge rotation need to match fan orientation?
Yes
What does system resistance curve represent ?
The sum of pressure losses in an hvac system
What is a vav terminal box ?
Designed to regulate the amount of air supplied to a space.
Pneumatic
Electric
Direct digital control
How is a vav controlled ?
Zone thermostat
What is another type of vav terminal unit ?
Vav bypass box which is used when the amount of air supplied to vav box cannot be changed. The excess air is ussally bypassed into the return air duct
What is the normal air Tempature supplied to a single duct vav ?
55 degrees Fahrenheit
If there a call for heat in one zone and cooling in another what can be done ?
Vav with reheat coil
What are dual duct terminals ?
Has hot and cold duct with a damper equipped with a mixing box.
Can have single damper or a double damper on both sides of the hot and cold duct
What is good practice to install in any type of branch fittings ?
Splitter damper
Where are air dampers used ?
To extract air from main duct into branch ducts.
Used when there is not adequate room to mount a splitter damper
What are 3 important functions of multiblade dampers ?
Control and mix outside air with return
Bypass heat transfer equitment
Control air quantities handled by the fan
What is a prallel blade damper ?
Has blades that roate parallel to eachother.
Used when system requires 2 positions
Fully opened or fully closed
What is an opposed blade damper ?
Blades that roatatw in opposite directions
Always recommended for volume
Control
How are damper blades controlled?
Automatic accuator
Pneumatic
Electric
What are inlet box dampers?
Used in clean air applications that use inlet boxes
These dampers are supplied with parallel blades for performance characteristics
What are iris dampers ?
Dampers for round that are fast and exact measurement, balance and control of airflow
What configuration does most residential equitment use ?
Counter clockwise UBD
What are the 2 types of commercial hvac systems ?
Constant air volume and variable air volume
What do most constant air volume systems do ?
Serve a single thermal zone
Can have variations such as reheat multizone primary secondary
Are constant air volume systems used in newer buildings?
Somewhat rare due to fan saving energy potential
When in heating and cooling mode what is the temp of the vav?
55 Fahrenheit for cooling
106 when heating
What are two types of vavs?
Regular vav system
True vav systems
Whst is the difference between regular and true vav systems ?
Regular dosent change the speed of the fans and instead uses dampers to throttle air
What are 2 advantages of vavs?
Can capacity control
Dehumidification
What does fan capacity control do ?
Reduces the energy consumed by fans
How are vavs controlled ? 3 ways
Pneumatically
Electronically
Automated
How much energy do vav systems save ?
20-30%
Whst are the 4 basic types of vav systems ?
Single duct
Dual duct
Bypass
True vav
What is a single duct vav and when should it be used ?
In buildings that have continuously warm climates and interior spaces that only require cooling like a hospital.
What happens when a zone is still to cool at minimum airflow ?
A reheat coil will be turned on or baseboard heater
Does the supply airflow rate vary in vav system ?
Yes when volume dampers are throttling
What is a dual duct vav?
2 seperate supply airflow ducts one has hot deck and one has cold deck
Provides thermal efficiency while maintains higher airflows
Where does the mixing occur on a dual duct system ?
Mixing box
What happens when the cooling airflow reaches a minimum on a dual duct system ?
The hot deck air increases in volume
What must happen for a bypass unit to operate properly ?
Be invisable to air handling unit
Located downstream of balancing damper
Balanced so pressure drop is the same
What is a true vav system ?
Reduces air at the terminal unit as well as the fan
Medium or high pressure and larger than bypass systems
Can be combined with baseboard or fan coil units or with constant volume perimeter systems
What are the 7 types of constant volume systems?
Single zone
Single duct zoned reheat
Multi zone system
3 deck multizone system
High velocity single zone systems
Dual duct systems
Induction units
How does a single zone system deliver air ?
Constant volume varying temp
How can you tell the difference between single duct with reheat and single zone systems ?
With reheat coils each vav has its own thermostat where single zone has one central thermostat
On a multizone system how are the decks arranged ?
Hot deck above the cold deck
Why are multizone systems inefficient ?
Cause of bucking
Means constantly cooling and heating the air at the same time
What’s the difference between multizone systems and 3 deck multizone systems ?
3 deck has a natural deck that’s not heated or cooled
When delivering air at a high velocity what is reduced ?
Duct size requirements
What is used with a high velocity system ?
Attenuator box
What are the 2 variations of the reheat system ?
Induction reheat system
Low temp reheat unit with induced air
What is an induction reheat terminal and where would you find it ?
Primary supply air blowing into unit directed by induction nozzle. Venturi effect
Find these units often under windows
When supply air is off the hot water in the coil will still provide some heat
Where are low temp reheat units with induced air used ?
Used where supply air temps are as low as 39 degrees Fahrenheit
Whst needs to be paired with a building exhaust system ?
Make up air unit
What are 4 benefits of makeup air units ?
Air can be heated or cooled
Improved indoor air quality
Decrease loads on existing hvac systems
Lower energy costs up to 35%
Can outdoor air be shut off when makeup air is not running ?
Yes shut off by damper assmebky
What are the two types of gas fired make up air units ?
Direct fired and indirect fired
What’s the difference between direct fire mua and indirect fire muas?
Direct has burner installed in airstream so products of combustion are exhausted into the building makeing it nearly 100%. Efficient
Indirect has a sealed flue for products of combustion to exhaust out
Can makeup air units utilize return air ?
Yes can be 50/50 or 80/20
What are the applications for direct gas fired muas ?
Heating or cooling
Space heating
Space pressure control
What are 3 types of makeup air applications ?
Direct compensating
General area
Door heater
Can a direct fired mua be used as a primary source of heat ?
Yes primary or secondary
Where should the return air be brought in for a mua ?
Downstream of the burner
What shall a direct mua not do ?
Shall not exceed the total discharge of the exhaust system by more than 10%
Where should a direct fired mua not be located ?
Not less than 20 feet horizontally from a vertical plane in which combustible gasses or combustibles are present
When direct fired mua is installed for ventilation of a storage grage Wgst must be used with it ?
Carbon monoxide sensor
Where can direct fired industrial heater not be used ?
Where sleeping accommodations are provided
What are commercial specs dived into ?
Divisions
What takes precedence specs or prints
Written specs always over blueprints
What are blanket specs ?
Means they may be used for all of the buildings in a certain geographic area
McDonald’s
Dollarstores
What do people refer to equitment specs as ?
Shop drawings
When designing a custom item what does the shop drawing become ?
Equitment spec
What is a change order ?
If changes are made to a project a change rider must be done so they can adjust the dollar figure
Best to document these changes immediately to protect contractors
What is an addendum ?
Similar to change order and sometimes tied to change order
Issued by the engineer usually while still in the design stage
Who creates the scheduling ?
Typically done by the mechanical or general contractor
What information is needed for crane scheduling ?
Weight of unit
Ensure reinforcement is done
Know how
Close crane can get to building
Height of building
Distance from edge of building to center of curb
How can drawing groups be divided ?
Site plans (location drawings)
Architectural drawings
Structural drawings
Mechanical drawings
Electrical drawings
Shop drawings
What do the letters a s m and e mean on blueprints ?
A architectural
S structural
M mechanical
E electrical
What should be done when familiarizing yourself with blue prints ?
Check index to see if the groups of drawings have been seperated
What are some critical dimensions on prints ?
Floor to deck heights
Holes that have to be sleeved
Should you assume plans are accurate ?
Never
What can be used to reference all major elements of a building ?
Grid lines
What is a call out ?
A letter or number in a box circle hexagon or octagon used to identify components described in the schedule
What is an hvac callout ?
Grille or diffuser type is the top then middle is collar size and bottom number is design cfm
What is the most crucial factor of determine building penetrations ?
Building codes
What are 3 types of penetrations ?
Wall
Floor
Roof
When are wall penetrations typically found ?
Exhaust and intake hoods or louvers
What might need to be done if doing a floor penatration in existing building ?
Floor may need to be xrayed
Is structural reinforcement required for all curbs and openings ?
Yes
When determining location for rtu what must be taken into consideration ?
Code clearances from exhaust ducts
Code clearances from walls minimum 2 feet
Code clearances from edges of roofs are met minimum 6 feet
Required service clearances for the unit being placed
What is the first thing to do before being your installation ?
Familarize yourself with the prints
Make sure prints are to scale by takeing some measurements of space
If changes are made to the blueprint as you you should document them for what ?
As built drawings
When should sleeping be done ?
When job is in initial stages and forms are being erected for walls and floors before the concrete is poured
What is a transit ?
Utilizes a reference point to determine baseline
How should balancing dampers be adjusted ?
From the main floor
What are trapeze hangers ?
Steel angle or u Chanel horizontally underneath the duct as a hnaher
What is strap hanger ?
Constructed 16 gauge galv steel usally 1”
Where are clutch and cable hangers useful ?
Seismic zones
What determines hanger spacing ?
Size and type of ductwork
7 to 8 feet apart for spiral
When can a common return air plenum be used ?
If there are no combustible materials in the space
On exhaust duct how far away should thermal insulation be installed ?
6 feet
If the ceiling is drywall where should thermal insulation damper be located ?
At the grillle or diffuser
What is the ceiling grid ?
Helps determine location for branch pipeong and trunk line
Where does the intersection of grid lines usually occur ?
Centerline of coloumns
What are the advantages of standard forms ?
Provide sequential documentation
Fab costs can be added
Quick references made
What must be done when ordering duct
Verify all site conditions when ordering duct
What are the 2 starting methods for an itemized list ?
Starting at equitment
Starting at branches and working way back
What should be the main concern when doing your own shop drawings ?
Accuracy and consistency
What should be included when writing a list for a job ?
Labelled
Job name
What items need to be listed ?
Hardware
Cleats
Hanger strao
What is a plenum ?
Duct connected to peice of equipment that is designed to create static pressure in the air before it release in the duct system
Can an extended plenum be the same the whole way through?
Yes can remain the same size all the way through
An extend plenum is one that is tapped into a box or primary plenum
What should be done when ordering a primary plenum ?
Make sure it fits the equitment it’s being attached to and can include 1” acc
What is the increase in size for a plenum takeoff ?
50% increase for the fasting side
When ordering acc lined duct what needs to be done to duct size ?
Increase duct size
When referring to side takeoffs what are the standard sizes ?
4 to 24 inches usally complete with a hammer lock
When referring to standard takeoffs what are the standard sizes ?
4-18”
Do balancing dampers come as standardized items ?
Yes
Spin in collars or tap in colours come in what sizes ?
4-14” as well as top takeoffs but universal takeoffs are usually only available in 4 5 6”
What size are 90 degrees elbows available in ?
3-24” same with 45 degree
How are pipe reducers for spiral available ?
Small end big end up to 24”
What length does aluminum rigid flex come in for lengths ?
10 feet
Do louvers commonly need to be custom ordered ?
Yes
How are fire dampers identified ?
Duct size and vh and ab
V=vertical
H= horizontal spring loaded
A = blades in air stream
B =blades out of airstream
What views should we draw for people in the shop ?
Simplest views
What do specs represent ?
Word description of the work that needs to be done
How are diffrent fissions of the specs represented?
Numbered and color coded
What do schedules do ?
Organize info
Diffrence between addendum and revision ?
Addendum change to spec
Revision change to print
Do addendums and revisions always take precedence?
Yes
What does a drawing legend consist of ?
Tables that show the drawing numbers and sheet titles
What do work drawings represent ?
Explains realationship between various specs
Shows the location height length and gauge thickness
What do architectural drawings include ?
Site plans floor plans extieror elevation views interior elevation views material specs building sectional views detail sectional view grid plan
What do engineered drawings include ?
Structural drawings
Mech drawings
Plumbing drawings
Electrical drawings
What do engineered drawings include ?
Structural drawings
Mech drawings
Plumbing drawings
Electrical drawings
Should you orally agree to a change ?
Never could be left with financial responsibilities
What is the maximum permissible length of flex duct ?
4 feet
What 2 reasons and residential and commercial systems multizone ?
Comfort and efficiency
What type of dampers are used for residential zoneing ?
Motorized dampers
What are motorized dampers controlled by ?
Central control panels
Zone dampers used in conjunction with what create a smart system ?
Ecm motor or variable speed dc motor
What are two types of bypass dampers
Barometric
Motorized
How can vav boxes be classified ?
As both pressure dependant and pressure independent
Independent measures volume in cfm
Dependent does not measure airflow will change depending on inlet static pressure
What are some common types of vav terminals ?
Dual duct non mixing
Dual duct mixing
Fan powered
Constant volume
Variable volume
Induction terminals
Vav diffusers
What does a dual duct mixing vav have to mix air ?
Perforated baffles
What is another classification of a constant volume fan ?
Series flow
What is another classification of a variable volume fan ?
Paraelle flow
What is the space air for an induction unit classified as ?
Secondary air
When is the blower energized on a vav
Heating
