HVAC Yr 2 Exam
When designing gas piping systems, the design pressure drop based on a natural gas specific gravity of 0.60 and an inlet pressure of 0.5 psig (14 in. wc), should be no more than __________ inches W.C.
0.5 HVAC Installation Procedures , pg.118 Figure 8-33
Type B vent pipe must be kept a minimum of ________ inch(es) from combustible materials or as specified by the vent pipe manufacturer.
1 HVAC Installation Procedures , pg.108
When hanging flexible duct, the hanging material should not be less than:
1 1/2 inches wide and spaced no further than every 4 feet
Fuel oil pumps are typically set at the factory to deliver oil at a pressure of:
100 psig
The most common manifold pressure for propane furnaces is:
11 inches wc HVAC Installation Procedures , pg.105
When installed in a hazardous location such as a residential garage, gas furnaces must be installed so that the burners are __________ inches above the floor.
18 inches HVAC Installation Procedures , pg.114
An extended plenum duct system works best when the length of of its supply and/or return trunk ducts do not exceed:
24 feet
Category IV furnaces can be vented using an existing chimney or vent and can be vented with another appliance.
False HVAC Installation Procedures , pg.110
The American Wire Gauge (AWG) is the standard used to express wire size. The higher the AWG number the bigger the wire diameter and ampacity.
False HVAC Installation Procedures pg. 91
Where do you measure the supply air temperature when checking furnace temperature rise?
In the main duct close to the supply air plenum HVAC Installation Procedures , pg.122
According to the National Electrical Code, which type of non-metallic sheathed cable can be used for both exposed and concealed work in both dry and moist locations?
NMC NEC Article 334.10 (B) (1)
Which is the best location for an outdoor condensing unit?
On the back or side of a house away from windows and overhangs
What type of vent is used for category IV gas appliances?
PVC vent HVAC Installation Procedures , pg.110
To limit the transmission of HVAC equipment vibrations into the conditioned space, a flexible connector should be installed where the supply and return ducts connect to the air handler.
True
Roof penetrations on bonded roofs can only be performed by the company that provided the bond or their recommemded agent.
True Refrigeration & Air Conditioning Technology , 7th ed. pg. 1538
Flexible conduit is commonly used with outdoor wiring of HVAC equipment and can be purchased in various lengths as preassembled "whips" complete with wire and fittings.
True HVAC Installation Procedures pg. 95
Under certain conditions, a rumbling noise will occur after the burner has cycled off on an oil fired furnace. This is probably caused by which of the following conditions?
after fire drip from the nozzle
The unit's location should be carefully selected so the system's operation is not adversely affected by air being able to:
flow freely through the condenser coil (WRONG) Refrigeration & Air Conditioning Technology , 7th ed. pg. 1538
What components on an oil furnace should be changed annually?
the fuel line filter and burner nozzle
The most reliable source for information regarding system installation is:
the manufacturer's installation manual
When installing a split system that has an indoor coil that is sized larger than the outdoor condensing unit, the metering device is sized to match:
the outdoor unit
Category I vent connectors shall be pitched upwards from the appliance at least:
1/4 inch per foot HVAC Installation Procedures , pg.109
The rating of a disconnect switch on fixed HVAC equipment must be at least _________ percent of the nameplate rated-load current or branch circuit selection current — whichever is greater.
115 NEC Article 440.12 (A) (1)
What size should the combustion air openings be for a mechanical room with an 80,000 BTU/hr furnace and a 35,000 BTU/hr water heater if the air is traveling through vertical ducts from an attic and crawlspace vented to the outside?
115,000 divided by 4,000 = 29 square inches free area each HVAC Installation Procedures , pg.116
The most common voltage system in use today is the ______________ system.
120/240 V — 60 HZ HVAC Installation Procedures pg. 87
What is the standard airflow across the evaporator of a 3 ton residential split system air conditioner?
1200 CFM
According to the National Electrical Code, single motor-compressor branch circuit conductors shall be sized so that they can carry ___________ percent of the rated load current or the branch-circuit selection current, whichever is greater.
125% NEC Article 440.32
What is the temperature rise of a furnace with a supply air temperature of 130°F, a return air temperature of 75°F, operating in an ambient temperature of 60°F?
130°F - 75°F = 55°F temperature rise HVAC Installation Procedures , pg.122
The maximum installed length of a flexible air connector is:
14 feet
Typically, the outdoor air ventilation rate adjustment on packaged units that allow for adequate outdoor ventilation airflow in a building should be about _____________ CFM per person.
15-20 HVAC Installation Procedures , pg. 149
According to the National Electrical Code, what is the minimum burial depth for a direct burial cable wired to an HVAC unit that must travel under a residential driveway?
18 inches NEC Article Table 300.5 column 1, one and two family dwelling driveways
According to the National Electrical Code, what is the minimum burial depth for a branch circuit wired to an HVAC unit under a residential driveway that is installed in an approved non-metallic raceway (conduit)?
18 inches NEC Article Table 300.5 column 3, one and two family dwelling driveways
What is the allowable ampacity of each conductor when 3 #10 THWN conductors are located in a raceway with an ambient temperature of 125 degrees F? Use Table 310.15 (B) (16) and Table 310.15 (B) (2) (a)
23.45 amps HVAC Installation Procedures pg.99 Step 1. Locate the amperage for #10 THWN conductors in Table 310.15 (B) (16) = 35amps Step 2. Locate the temperature correction factor for 125 degrees F under the 75 C column of Table 310.15 (B) (2) (a) = 0.67 Step 3. Multiply the amps times the correction factor. 35 x 0.67 = 23.45 amps
According to the National Electrical Code, a continuous load means the load is rated at full load amperage for?
3 hours or more NEC Article 100 Definitions - continuous load
The most common manifold pressure for natural gas furnaces is approximately:
3.5 inches wc HVAC Installation Procedures , pg.122
The condensate line from the drain pan of the evaporator is normally:
3/4 inch plastic tubing
Threads on ½" to ¾" black iron pipe installed on gas appliances should be __________ long and have approximately__________ per end.
3/4 inches, 10 threads HVAC Installation Procedures , pg.67 Table 5-1
To prevent condensate pan overflow, the condensate trap outlet on both slab and roof mounted package units should be located at least ______________ lower than the outlet condensate connection.
4 1/4 inches HVAC Installation Procedures , pg. 153
On a sheet metal duct system, the first branch duct takeoff downstream of the main duct reducing transition should be located at least ____________ away to allow the air turbulence resulting from the duct transition to diminish.
4 feet
When installing rooftop package units on a flat roof, the roof curb should be at least ___________ above the highest water level expected.
4 inches HVAC Installation Procedures , pg. 153
According to the National Electrical Code, when a disconnect is required to be within sight, it must be visible and cannot be located more than __________ from the load.
50 Feet NEC Article 100 Definitions - In sight from
After installation, the indoor coil and line set should be leak tested with nitrogen and evacuated to below:
500 microns
The input Btu rating of a gas furnace is 75,000 Btu. The gas heating value of one cubic foot of natural gas is 1030 btu. Calculate the cubic feet per hour of gas the furnace requires to operate. (Rounded up to whole numbers)
73 CFH HVAC Installation Procedures , pg.118
What size should the combustion air ducts be for a mechanical room with an 60,000 BTU/hr furnace and a 16,000 BTU/hr water heater if the air is traveling through horizontal ducts from the outside?
76,000 divided by 2,000 = 38 square inches free area each HVAC Installation Procedures , pg. 116
According to the National Electrical Code, the minimum length of a grounding rod or pipe shall be:
8 feet NEC Article 250.52 (A) (5)
Which class of manufactured fexible duct support material meets the surface burn testing ratings of 25 flame spread and 50 smoke developed maximum?
Class 1
A rule of thumb says that for every one inch of fiberglass duct insulation the equivalent R-value would be about R-4.
True
Long runs of flexible duct are not recommended, even when installed properly, because flex duct has at least two to four times as much resistance to airflow as sheet metal duct.
True
Split system AC units installed with line sets longer than 50 ft, you should consult the manufacturers instructions ?
True
Splices made to join electrical wires must be made inside an electrical box or enclosure using approved connectors.
True HVAC Installation Procedures pg. 96
What type of vent is designed specifically for category I gas appliances?
Type B vent HVAC Installation Procedures , pg.107
All tapes and mastics used for field installation of flexible duct shall be listed and labeled to standard:
UL 181B
A manufactured air duct that meets all UL tests is classified as:
a flexible air duct
HVAC equipment installed in an attic is not required to have which of the following?
a light with a separate switch (wrong) an auxiliary 120 volt receptacle (wrong) NEC Article 210.63, & 210.70 (C)
When evaluating combustion and ventilation requirements for furnace equipment in confined spaces, a confined space is defined as:
a space having less than 50 cubic feet per 1000 Btuh of combustion equipment input HVAC Installation Procedures , pg.115
Most rectangular sheet metal ducts are joined together using:
a. snap joints b. S-locks and drives cleats d. both a and b are correct
A precisely drilled hole that controls the amount of gas entering a burner is called:
an orifice HVAC Installation Procedures , pg.106
On split heat pump systems operating in the heating mode, the term reverse cycle heat means:
b.the outdoor coil becomes the evaporator and the indoor coil becomes the condenser c.heat travels from the outdoor air via the outdoor coil to the indoor air via the indoor coil d.both b and c are correct
According to the National Electrical Code, a # 6 grounding conductor is identified by which of the following methods?
bare, green or green with yellow stripes NEC Article 250.119
The raised, rectangular sheet metal frame that a rooftop unit rests on is called a:
curb HVAC Installation Procedures , pg. 152
If the temperature rise of a furnace is too low, how can it be increased?
decrease the blower speed HVAC Installation Procedures , pg.122
Which measurements are the most important to insure proper combustion when setting up a new oil furnace?
draft, smoke test, net stack temperature, and carbon dioxide percentage
According to the National Electrical Code, how is a size 6 or smaller grounded conductor identified?
either white or natural gray covering or three continuous white stripes on other than green covering NEC Article 200.6 (A) (1), (2), & (3)
According to the National Electrical Code, non-metalic cable must be protected by which method where passing through floors?
enclosed in an approved conduit extending at least 6 inches above the floor NEC Article 334.15 (B)
On Category I gas appliance main vent systems, what must be installed where the vent passes through floors and ceilings?
fire-stop HVAC Installation Procedures , pg.108
To avoid cutting extra holes in the roof, power is normally provided to curb mount rooftop units:
from underneath through the curb Refrigeration & Air Conditioning Technology , 7th ed. pg. 1543
Water and air leakage between the rooftop unit and the rooftop curb are prevented by:
gasket material between the curb and the unit HVAC Installation Procedures , pg. 152
According to the National Electrical Code, UF cable is permitted to be used in which of the following locations?
in wet, dry or underground locations NEC Article 340.10 & 340.12
Furnace gas manifold pressure is measure in:
inches water column HVAC Installation Procedures , pg.122
If the flame of an oil burner hits the wall of the combustion chamber before it is totally ignited the result will be :
incomplete combustion
Which of the installation steps listed is normally performed first?
leak testing the system
It is good field practice to double check and possibly triple check the ____ decision, since the cost of repairing an improperly cut roof can be very high.
location Refrigeration & Air Conditioning Technology , 7th ed. pg. 1538
Which of the following piping items should be installed in the gas line ahead of a gas furnace or appliance.
manual gas shutoff valve sediment trap flexible connector or pipe union all of the above items should be installed HVAC Installation Procedures , pg.119
When a rooftop package unit equipped with an economizer is operating during periods when the outdoor air temperature is too warm, the outdoor ventilation air damper should be in the:
minimum outside air position Refrigeration & Air Conditioning Technology , 7th ed. pg. 1546
When performing a smoke spot test, the lighter color sample number achieved during the test represents:
more complete combustion
Compared to the overfire draft, the flue draft should be:
more negative than the overfire draft
The electrical disconnect box for a rooftop unit is typically:
mounted on the unit HVAC Installation Procedures , pg. 154 which refers you back to Section 7. See page 91 also.
When installing rooftop package units, the condensate drain:
must comply with local codes HVAC Installation Procedures , pg. 153
The condensate drain on a rooftop unit:
must include a trap unless the unit has an integral trap HVAC Installation Procedures , pg. 153
Which of the following oil burner nozzle characteristics would be most affected by the shape of the combustion chamber?
nozzle spray angle
Before beginning the installation, the first thing the installing technician should do is:
read the installation instructions and make a list of materials
If the roof curb for a package AC unit is mounted as part of a new construction process, it can be assembled and installed as soon as the ____ support system is in place.
roof Refrigeration & Air Conditioning Technology , 7th ed. pg. 1539
According to the Carrier Installation manual, when performing start-up and checkout on a gas furnace after installation, what should the proper temperature rise across the furnace be adjusted to equal?
slightly above the range on the name plate rating HVAC Installation Procedures , pg.122
Proper height above the roof is important when installing a heat pump rooftop unit:
so that snow does not block airflow through the outdoor coil Refrigeration & Air Conditioning Technology , 7th ed. pg. 1538
On a package unit equipped with an economizer that has a fixed enthalpy sensor, the sensor includes:
solid-state temperature and humidity sensors Refrigeration & Air Conditioning Technology , 7th ed. pg. 1546
The amount of heat absorbed by the heat exchanger of an oil furnace is frequently decreased because of:
soot accumulation
When performing a system start-up and checkout on a split system AC unit equipped with a piston type metering device, the proper system charge is verified using which of the following methods?
subcooling method (WRONG) HVAC Installation Procedures pg. 145
To connect a round branch duct to a rectangular metal main duct, a ___________ fitting is used.
take-off
Rooftop units can have the ductwork connected to either:
the bottom or side of the unit HVAC Installation Procedures , pg. 151
Rooftop units should be leveled when they are installed so that:
the condensate can drain properly HVAC Installation Procedures , pg. 152
One of the major determining factors in the location of a rooftop unit will be:
the distance that a crane can reach over the edge of the building Refrigeration & Air Conditioning Technology , 7th ed. pg. 1538
When using the face-to-face method for measuring and cutting steel pipe, what must be considered in determining the length of the pipe to be measured, cut and threaded?
the face-to-face distance plus the depth of thread engagement times two HVAC Installation Procedures , pg.66
What type of information is necessary to use a Carrier gas manifold pressure calculator or a manufacturer's gas manifold pressure chart?
the size and number of burner orifices, the furnace input btu/hr and gas heating value HVAC Installation Procedures , pg.121
How is the net stack temperature of an oil furnace calculated?
the temperature difference between the stack temperature and the ambient temperature around the furnace
Where is solid 18 gauge copper wire typically used in residential air conditioning installation?
the thermostat control wire
What is a vent connector?
the vent connector is the metal pipe running from the furnace to the main vent HVAC Installation Procedures , pg.108
When installing a reducing extended plenum duct system, a reduction in trunk duct size generally is made after every _________ branch duct connections.
three
How does the amount of excess combustion air affect the the percentage of carbon dioxide measured in the flue gas?
too much excess air reduces the percentage of carbon dioxide measured in the flue gas
Gas fired rooftop units are normally vented though:
vent hoods connected directly to the unit HVAC Installation Procedures , pg. 154
Liquidtight flexible non-metal conduit shall be securely fastened and supported:
where lengths exceed 6 ft, at 3 ft intervals and within 12 in. of boxes NEC Article 356.30 (1)
