Heating System Flashcards
_____ occurs when heat is transferred through solid matter.
conduction
_____ occurs when heat is transferred by circulation of gas (air) or liquid.
convection
_____ occurs when heat is transferred by absorption of electromagnetic energy in the infrared part of the spectrum.
radiation
Incomplete combustion produces more _____ _____ than complete combustion and other compounds such as _____ _____ and _____ also known as _____, which can indicate a significant combustion issue in a gas appliance.
water vapor
carbon monoxide
carbon
soot
Incomplete combustion in solid fuel burning appliances ,such as wood, can create _____, a flammable substance described as _____ (stage 1), _____ (stage 2), or _____ (stage 3). Stage 3 is highly _____ and quite _____ to _____.
creosote
light brown or black flaky ash
heavy tar-like ash
hard and shiny coating
flammable
difficult to remove
In modern construction combustion air should be drawn from _____ the house, since modern energy codes require homes to be _____ _____.
outside
air sealed
_____ _____ _____ is the area of an opening minus the space occupied by screens, louvers, or other obstructions. The minimum opening dimension is _____ inches for openings serving combustion air intake.
Net free area
3 1/2
Drawing combustion air from the same room is called the _____ _____ and requires at least ___ cubic ft. of volume in the room for every _____ BTU/H input of the appliances in the room.
standard method
50
1,000
If combustion air is drawn from adjacent rooms on the same story, there should be ___ openings between the rooms, one within ___ in. of the floor and the other within ___ in. of the ceiling. Each should have at least ___ sq in. net free opening area for every _____ BTU/H input from the appliances in the room.
2
12
12
1
1,000
If combustion air is drawn from different stories, there should be ___ or more openings having a total combined net free opening area of at least ___ sq in. for every _____ BTU/H input from the appliances in the room.
1
2
1,000
In gas appliances, combustion air may be provided from outside the house if provided by ___ openings in the wall or by ___ ___. One opening should be within ___ in. of the floor and another should be within ___ in. of the ceiling. Air net free opening area for openings and vertical ducts is ___ sq in. per _____ BTU/H input or ___ sq in. per _____ BTU/H input for horizontal ducts.
2
2
ducts
12
12
1 per 4,000
1 per 2,000
Gas appliances may be provided combustion air from outside the home using ___ opening(s) in the wall within ___ in. of the ceiling. The net free opening area should be at least ___ sq in. per _____ BTU/H input of the gas appliance in the room
1
12
1
3,000
Masonry fireplaces should have a combustion air duct that terminates _____ or in a _____ _____ _____ which should be _____ or _____ the firebox height. The interior termination may be on the _____ or _____ of the firebox or within ___ in. of the firebox opening.
outside
ventilated crawl space
at or below
back or sides
24
Combustion air ducts should be a minimum of ___ gauge galvanized steel. Minimum duct dimension is ___ inches. _____ _____ and _____ _____ may not be used. _____ and _____ cavities may be used if not more than ___ fire block is removed.
28
3
flexible duct and duct board
stud and joist
1
Gas burning or oil burning appliances should not be located in _____, _____, _____, or _____ unless the appliance is _____ _____ and obtains all combustion air from _____ or a space that is weather stripped and obtains all combustion air from _____.
bedrooms, bathrooms, closets, or spaces that open into these spaces
direct vented
outside
outside
Spaces with appliances competing for combustion air should be inspected for signs of _____ _____ and _____.
incomplete combustion
backdrafting
_____ _____ replaces air removed by appliances such as clothes dryers, kitchen exhaust hoods, and bathroom exhaust fans. It is especially necessary when these appliances are in the same space as _____ _____ _____.
makeup air
fuel burning appliances
Fuel burning appliance closets or compartments should be _____ and _____ when combustion air is drawn from outside.
sealed and insulated
HVAC loads are determined using protocol set forth in _____ _____. Those loads are then used to find recommended system capacity set forth in _____ _____.
ACCA Manual J
ACCA Manual S
_____ _____ _____ pump a heated liquid through pipes that may be installed in the floor or that run through radiators or similar devices.
Hydronic distribution systems
_____ _____ move heat by heating a material and allowing the heat to flow by radiation, conduction, and convection.
Radiant systems
_____ _____ and _____ _____ _____ systems often require significant effort and time to begin operation and obtain a reliable test observation, and for this reason inspectors may elect not to operate the system, however should report that it was not operated and why.
Hydronic systems
solid-fuel burning
Category __ appliances vent gas that is hot, around 300 degrees F, which rises through the vent by being less dense and more buoyant that’s surrounding air, also know as the _____ _____.
I
stack effect
Category ___ appliances vent gas that is hotter than 300 degrees F and their vents are under _____ _____. ______ can be a problem but these appliances are not considered condensing.
III
positive pressure
condensate
Category ___ appliances vent gas that is cool, around 140 degrees F and vent under _____ _____. These are _____ appliances and require _____ disposal
IV
positive pressure
condensing
condensate
The _____ _____ is the heart of a gas forced air furnace. It is heated by gas fire making it hot, and a fan pushes air across it. Any cracks in the _____ _____ can allow _____ _____ to enter the air flow of the house which is a major _____ _____.
heat exchanger
heat exchanger
combustion gases
safety concern
_____ gas connectors are not allowed to enter appliance cabinets.
Flexible
Draft hood type gas furnaces are Category ___ gas furnaces that are _____ efficiency, or about ___%. These furnaces often have 3 to 6 _____ _____.
I
low
65
ribbon burners
Induced draft type gas furnaces are the most common type of Category ___ furnace. They are _____ efficiency, about ___% and often have 2 to 6 _____ _____.
I
medium
80
inshot burners
In a gas furnace, the presence of wires spliced together near controls could indicate _____ _____ _____ _____, which is a reportable defect. Cables should enter the cabinet through a _____.
bypassed automatic safety controls
bushing or grommet
The ignition sequence for a draft hood type furnace consists of a click when the _____ _____ opens, _____ignition, and _____ _____.
gas valve
burner
fan activation
The ignition sequence for an induced draft type furnace consists of draft inducer _____ _____, _____ _____ activation, a _____ when the gas valve opens, _____ ignition, and then_____ activation.
fan activation
ignition device
click
burner
fan
Burners in a gas furnace that are burning properly will have a _____ flame which may possibly have a _____ tip. A _____ or _____ flame is a reportable defect which indicates an improperly adjusted _____ _____ or inadequate _____ _____.
blue
slightly yellow
yellow or orange
gas valve
combustion air
A flickering or distorted burner flame could indicate a cracked _____ _____, which is often more visible with _____ burners than _____ burners.
heat exchanger
ribbon
inshot
Inspecting Category ___ gas furnaces is similar to Category I, however these furnaces have one or two _____ _____ _____ that will connect to a collection _____ and then to the evaporator coil condensate drain. These tubes should not be _____ and should be _____ to drain towards the _____. The condensate is usually _____, which will cause damage to sheet metal enclosures.
IV
condensate drain tubes
tank
crimped
sloped
tank
acidic
When appliances are installed in garages, they should be protected from _____ _____ by framing or some type of _____ _____. Ignition sources such as burners should be located at least ___ inches above the garage floor.
vehicle impact
vehicle stop/bollard
18
Floor furnace _____ should be located in the same room as the furnace.
thermostats
Gas floor furnaces are Category ___ and should not be installed in _____ or _____. The furnace grille should be at least ___ in away from walls and at least ____ in away from at least one wall if placed in a corner. The grille should also be at least ___ in from materials such as curtains or any position that a door may reach.
I
bedrooms or bathrooms
6
18
12
Gas floor furnace grilles should be at least ___ ft below projecting combustibles such as shelves and the bottom of the furnace should be at least ___ in above the crawl space floor. The bottom should not project into _____ _____. The draft hood requires at least ___ in to combustibles such as floor joists.
5
6
habitable spaces
6
Gas floor furnaces require a type ___ vent and connector or appropriate _____. Oil floor furnaces require a type ____ vent and connector or appropriate _____. Single wall vent connectors may not be used in _____ _____.
B
chimney
L
chimney
crawl spaces
Wall furnaces should be ___ in from a door in any position, at least __ to __ in from wall corners, and at least __ to __ in from ceiling or other materials projecting from above. Most manufacturers recommend a _____ _____ and _____ _____ between the unit and carpet.
12
4 to 6
12 to 18
metal plate
physical distance
Most gas wall furnaces use a type ___ vent which resembles a type B vent with _____ shape. Wall furnaces may not use a _____ as a vent.
BW
oval
chimney
Vented room heaters may not be connected to _____ or _____ that serve other rooms. They may use a type ___ vent or a ____ if approved by manufacturer. The shut off valve may be located in another room if the valve is permanently _____, _____ _____, and _____ _____ _____ _____.
ducts or registers
B
chimney
labeled
readily accessible
serves no other appliance
Government estimates show that unvented gas appliances cause _____ fires and _____ deaths each year.
25,000
300
_____ gas appliances should not be installed in newer construction that adheres to modern energy codes, due to air sealing requirement in new homes.
unvented
Unvented room heaters require side clearances of ___ in, to combustible trim of at least ___ in, top clearances of at least __ in, hearth extension depth of __ in. A heat resistant material such as _____ or _____ should be installed ___ in vertically above firebox opening.
16
6
42
14
12
Unvented appliances should not be used in a room unless it contains at least __ cubic ft of volume for every ___ BTU/H input from the unit.
1
20
Unvented appliances may not be used in bedrooms or bathrooms except one wall mounted unit may be used in a bathroom if appliance BTU/H is _____ or less and bathroom has volume for combustion air, or in a bedroom if the appliance BTU/H is _____ or less and bedroom has sufficient volume for combustion air.
6,000
10,000
Category I vent systems consists of a manufactured _____ _____ or _____, a _____ _____, and a _____ _____.
vent pipe or chimney
vent cap
vent connector
Category I vent systems use a type ___ vent or _____. A _____ _____ _____ is allowed in warmer climates only, since these pipes lose heat more rapidly and do not conduct combustion gases out of the vent as effectively.
B
chimney
single wall pipe
A Category I vent system serving multiple gas appliances is called a ____ ____ ____.
common vent system
When using a masonry chimney as a Category I gas appliance vent the chimney must be _____ _____ the house until it _____ _____ _____.
enclosed within
penetrates the roof
A chimney being used as a Cat I vent may not serve as a vent for a single _____ _____ _____, however it may serve as the vent for multiple _____ _____ or _____ _____ equipped gas appliances.
induced draft furnace
induced draft
draft hood
When used as a Cat I vent, a chimney must be at least as _____ as the vent connector area and smaller than _____ times the vent connector area if serving as vent for a single _____
_____ equipped appliance.
large
7
draft hood
Cat I, type B vents require __ in clearance to combustibles. Single wall pipe vents require __ in. Combustible materials include _____, _____ _____, _____, and _____.
1
6
insulation
electrical cable
ducts not made from sheet metal
wood
Type B vent terminations should have __ ft horizontal clearance from a vertical sidewall or __ ft vertical clearance of any obstruction within __ ft. Single wall pipe terminations requires __ ft vertical clearance above any obstruction within __ ft. Obstructions include all _____ _____ _____ _____ such as windows and eave ventilation.
8
2
10
2
10
gravity air intake openings
All gas vents should terminate at least __ ft horizontally or __ ft vertically from mechanical air intake openings, such as an _____ _____ _____ _____ or _____ _____ _____ _____.
10
3
energy recovery ventilation system
Heat recovery ventilation system
Sections of vent pipe should be secured together with at least ___ screws or a manufacturer approved _____. Disconnected or inadequately connected vent pipe components are a _____ hazard and an _____ _____ _____ due to _____ _____.
3
connector
fire
air quality hazard
carbon monoxide
Vent systems should extend at least __ ft above the flue collar or draft hood, __ ft above the bottoms of a gas wall furnace and should not extend more than __ ft.
5
12
50
Vent connector slope should be at least _____ upwards toward the vent.
1/4” per 12” (1/4 / 12)
Single wall galvanized steel pipe of at least __ ga thickness may be used as vent and vent connectors.
28
Flexible type B vents may not penetrate _____, _____, _____ nor may they be used in _____ or _____. Additionally, flex vents may not be bent more than ___ degrees, may not be _____ or _____, and may not be compressed more than __ in per foot.
walls, floors, ceilings
attics or crawl spaces
90
cut or modified
4
In cold climates, single wall pipe may not be used as vent pipe in _____, _____ , or _____. In all climates, it may not penetrate _____ or _____, but may penetrate directly through the _____ if clearance to combustibles of __ in is maintained.
attics, crawl spaces, or garages
floors or ceilings
roof
6
Many manufacturers do not recommend the use of _____ wall pipe. Unapproved use is a _____ _____ and a _____ _____.
single
fire hazard
backdrafting hazard
If a vent connector length is _____ or _____ the vent system height or if the vent system contains elbows that total more than ___ degrees in bends, inspectors should recommend evaluation by a qualified _____ contractor.
equal to or greater than
180
HVAC
A common vent connector should not be more than _____ times longer (IN FEET) than it’s diameter in inches.
1 1/2
Common vent connectors may enter the vent at the same level horizontally but should do so at a ___ degree angle. Connectors may enter at ___ degree angles only if they do so at different levels horizontally.
45
90
Appliances on different _____ should not share a common vent unless approved by an _____.
stories/floors
engineer
A vent connector should not be closer than it’s own _____ to the opposite side of a chimney from the side in which it entered.
diameter
Where a vent connector enters a chimney, it should be _____ and _____.
secured and sealed
Cat III direct vented appliances use _____ _____ _____ pipe for vent systems. It often consists of __ concentric pipes, one inside the other, with the _____ in the center and _____ ___ drawn through the outer pipe. They must be sealed because the vent is under _____ _____. The pipe is often made of ______ _____.
manufacturer recommended metal
2
vent
combustion air
positive pressure
stainless steel
Cat IV appliances use _____ pipe for venting and combustion air intake. Manufacturers recommend it be supported every ___ to ___ ft and sealed with _____ _____ using both _____ and _____.
plastic
3 to 5
solvent cement
primer and cement
The vent and combustion air pipes in Cat III and IV appliances should terminate in the same _____ _____ and on the same _____ _____ or _____.
pressure zone
roof section or sidewall
In regards to clearances, there are many different illustrations and charts for _____ _____ and _____ _____ appliances. Different _____ have different clearances and those clearances differ even further depending on the ___ input if the appliance.
direct vented and direct exhaust
manufacturers
BTU
The only clearance requirement among Cat III and IV appliance vent terminations that is consistent among different manufacturers is that both vent and combustion air pipes should terminate at least ___ in above grade or above local snow accumulation height, whichever is _____.
12
higher
The most common type of oil burner heating system is the _____ _____, also called the _____ _____ burner.
gun-type
atomizing-type
The flame from a modern oil burner should be _____. A small amount of _____ is permissible. Flame colors between _____ and _____ indicate _____ flame temperature and oil burner issues. The flame should be uniform and consistently around __ in wide at the widest point and should not touch or _____ the surfaces of the _____ _____.
white
yellow
orange and red
cooler
5
impinge
refractory chamber
Absence of an oil burner _____ _____ _____ _____ is a significant safety defect. This sensor detects the presence of a _____. It shuts off the _____ if not detected. Newer sensors are called _____ _____ _____ or _____ _____ _____ and detect _____. Older sensors are called _____ _____ and detect heat.
flame shut off sensor
flame
burner
cadmium cell sensors
fire eye sensors
light
stack relays
Oil can collect in the refractory and ignite causing _____ if the ___________ sensor is not working. The sensor has a _____ _____ switch, which can only be pressed once before attempting to re-ignite. If it continues to fail after this, a _____ _____ should evaluate. Inspectors should _____ press this switch.
puff back
Oil burner flame shutoff
red reset
HVAC technician
never
An ___ ___ ___ ___ is a fire safety device that shuts off oil flow if there is a fire.
oil line safety valve
An oil burner electrical shutoff switch should be located at the ___ ___ ___ ___ when an oil burner is located in a basement.
top of basement stairs
Oil burners may use a type __ vent, a _____, or _____ _____ metal pipe that is at least __ ga thickness. If using a _____ it should be equipped with a _____ _____. Oil burners may not use a type __ vent.
L
chimney
single-wall
26
barometric damper
B
The purpose of a _____ _____ is to control draft conditions in the vent system.
barometric damper
In oil burning appliances, type L vents should have at least __ in clearance to combustibles. Single wall pipe should have __ in. The barometric damper should have __ in clearance.
3
9
18
The vent system of oil burning appliances should be at least __ ft above the highest flue collar or draft hood and at least __ ft above the bottom of the appliance.
5
12
Distributed electric heaters should be served by a _____ _____ _____.
dedicated electrical circuit
Electric radiant heaters require a _____ circuit when installed in a bathroom, kitchen, or near massage tubs, spas, or hot tubs
GFCI
Modern hot water heating systems are _____ systems, and once the system is filled with water it should be _____. The normal operating pressure of the these systems is around __ psig to below __ psig. The normal operating temperature is between ___ F and ___ F, with a range between ___ F and ___ F being most common.
closed
sealed
20 to 30
120 degrees to 200 degrees
160 degrees to 180 degrees
Boilers sometimes provide domestic hot water through components such as _____ _____, _____ _____ water heaters, or _____ _____.
tankless coils
Indirect-fire
Range boilers
A device that controls when a hot water boiler activates or fires is called an _____.
aquastat
Residential boilers usually have a _____ _____ _____ set for __ psi. Inspectors should confirm that the correct _____ is being used by checking the boiler rating plate.
Pressure relief valve
30
Valve
Boilers should have a relief valve extension pipe that may terminate within __ in above the floor to an _____ _____ _____. All other requirements for this pipe are the same as water heaters.
18
Open waste receptor
All components of a hot water heating system should be _____ _____ _____ _____. There should be a method for bleeding air from the system, but lack of one is not a deficiency.
Completely filled with water
Hot water heating systems should have an _____ _____ and shut off _____ near the boiler.
Expansion tank
Valve
Steam heating systems are divided into ___ _____ systems with pressure between __ psig to __ psig, _____ _____ systems, which are less than __ psig, and _____ _____ systems, which are over ___ psig.
Low pressure: 1/2 to 2 psig
Vapor pressure: less than 2 psig
High pressure: over 15 psig
The normal standby temp for steam heating systems is between _____ and _____F. Operating temp is around _____F.
180 and 200 degrees F
212 degrees F
A steam heater pipe must be sloped a minimum of _____ toward the boiler for effective flow of water back to the boiler.
1 in per 10 ft
_____ _____ _____ systems have a high potential for a fight between steam and water.
One pipe counter-flow
In a _____ _____ _____ _____ system, water and steam travel in the same pipe until the last distribution device, then the water is carried back to the boiler in a separate pipe from the steam. A minimum slope of _____ is recommended toward the boiler.
One pipe parallel flow
1 in per 20 ft
In a one pipe parallel flow system, the water return pipe is below the water level of the boiler, and is therefore called the _____ _____. If this component leaks the boiler could _____ _____.
Wet return
Run dry
All steam heating systems with wet returns should have a _____ _____ and a _____ _____ to prevent the boiler from _____ _____.
Equalizer pipe
Hartford loop
Running dry
Steam pipes are required to be _____, while water return pipes _____. Insulation on older pipes could contain _____.
insulated
are not
asbestos
Steam heating systems should have at least one _____ _____, which may be a _____ _____ _____ or an _____ _____ _____, one of which should be located within __ in above the boiler water line and _____ in above the dry return pipe.
Main vent
Ball float trap
Inverted bucket trap
18
6 to 10
Each heat distribution device in a one pipe steam system should be equipped with an _____ _____ near the _____ _____ of the device. A _____ or _____ after the heating cycle starts indicates a reportable defect as it indicates that it may be blocked.
Air vent
Vertical center
Hissing or sputtering
Each heat distribution device in a two pipe steam system should be equipped with a _____ _____. A _____ _____ coming from it could indicate that it is defective. It’s service life is between __ and __ years.
thermostatic trap
Rapid sound
3 and 5
Two pipe steam heating systems should be equipped with a ____ and _____ trap or ___ trap. The purpose of this trap is to allow ___ and ___ that collects in the steam supply to pass, but not allow ___ to escape.
float and thermostatic
F&T
air and water
steam
A ___ ___ ___ ___ should be installed on boilers to shut off the boiler if water ___ ___ ___ level.
Low water shutoff switch
drops below minimum
A ___ ___ ___ or a ___ ___ ___ ___ should be installed on boilers. This valve is usually a ___ psi/___F valve. The valve requires an extension pipe that may terminate within ___ in of the floor or to an ___ ___ ___.
pressure relief valve
temperature/pressure relief
15 psi/250 degree F
18
open waste receptor
The device that controls steam pressure in a steam heating system is usually a _____ or a _____.
pressuretrol or vaporstat
Banging in pipes is also known as _____ _____. This condition is a ___ and should be ___.
water hammer
deficiency
reported
A humidifier should not be installed on a _____ _____, but instead on a _____. Humidifiers should not be installed in _____ areas subject to _____. If equipped with a bypass duct it should be made of _____ and not ____ ____ ____. The bypass duct should be equipped with a _____ that should be inserted or closed when the air conditioner is _____.
furnace cabinet
plenum
unconditioned
freezing
metal
flexible plastic duct
damper
operating
Shower and bathtub valves should be equipped with a device that limits max water temp to ___ F, however home inspectors are not required to test this function.
120° F
Single handle shower valves should have ____ set so that the valve handle does not turn past a ____ ____ and so that the water temperature is ____ over a reasonable ____.
stops
certain point
adjustable
range
Hose connection faucets are commonly called ____ ____, ____ ____, ____ or ____ ____ depending on the region. These valves are designed for attachment to a ____ ____ such as a ____or ____. They are usually ____ valves.
hose-bibs, sill-cocks, spigots, or hose- cocks.
permanent support
building or post
compression
A ____ ____ is a hose connection valve that is intended to be self-supporting and installed away from buildings in areas where structural support is not available. They are common in rural areas.
yard hydrant
Hose connections subject to freezing should have a ____-____-____ valve, which enables the homeowner to shut off the water from an area not subject to freezing and allows the remainder of the valve mechanism to drain ahead of a freezing event or season. An alternative to this is the ____ ____ ____ ____, which have a long valve stem and pipe that extends into a warmer area that prevents the faucet from freezing.
stop-and-waste valve
frost proof hose connection
Inspectors who practice in cold climates should report the presence of ____ ____ ____ that do not have a means to shut off and drain.
hose connection faucets
An ____ injects air into the water stream from a faucet. This helps prevent water from ____ when ____ the sink surface. This component can become blocked causing ____ ____ ____.
aerator
splashing when hitting
low functional flow
A ____ ____ is often installed in a faucet to limit the water flow rate. It is described as a plastic disc with ____ ____. This component can become blocked causing ____ ____
____.
flow restrictor
small holes
low functional flow
Sink faucets have a maximum water flow rate of ___ gallons per minute. Shower heads have a max flow rate of ___ gallons per minute.
2.2
2.5
Faucets and valves that supply hot and cold water should have the hot valve or setting on the ____ and the cold valve or setting on the ____. This can be reversed, but only if the valves or settings are ____ to indicate hot or cold.
left
right
labeled
A bathtub equipped with a pump and motor and sometimes a water heater is known as a ____ ____ or ____ ____. Inspectors should not refer to these fixtures by the brand name ____.
whirlpool tub or hydro-massage tub
jacuzzi
Common bathtub size is ___ by ___.
30” by 60”
Bathtub drain outlets should be at least ___ “ in diameter and should include a ____ underneath. The fixture drain length should be no more than ___ ‘ long.
1 1/2”
p-trap
6’
Bathtubs should have adequate ____. Excessive ____ can cause movement of plumbing causing leaks, can cause the tub to crack, and can cause the tub to ____ away from the drain. Inspectors should ____ ____ bathtubs and report any significant ____.
support
deflection
slope
step inside
deflection
A whirlpool bathtub should bear completely on floor ____, on a platform that completely ____ the bathtub bottom, or on a bed of ____ or ____.
sheathing
supports
concrete or plaster
Floor joists supporting a bathtub should not be ____ or ____. This is a reportable defect and is commonly seen in order to accommodate the ____ ____.
cut or notched
bathtub drain
Bathtubs should be equipped with a water tight ____, and an ____ ____. ____ ____ should be tested, ____ should not.
stopper
overflow opening
mechanical stoppers
overflow openings
Whirlpool bathtub pump should be readily ____ for ____ and ____. The minimum clear opening size is ___ by ___ or ___ by ___ if the pump is 2 or more feet from the opening. There should be no ____ between the opening and the pump.
accessible for service and repair
12” x 12”
18” x 18”
obstructions
A shower drain outlet should be at least ___ in diameter. A drain not more than ___ ft long requires a 1 1/2” p-trap, and drains not more than ___ ft long require a 2” trap.
1 1/2”
6
8
Minimum diameter shower size from finished wall to center of curb or threshold is ___ if the total floor area is at least ____ sq in. The minimum diameter drops to ___ in if the total floor area is at least ____ sq in.
30”
900 sq in.
25”
1,300 sq in.
