Nate Exam

Front 1

Face velocity of a supply register should be?

Back 1

500 to 700 fpm

Front 2

Face velocity of a return grille should be limited to

Back 2

400 fpm

Front 3

If a packaged heat/cool unit is equipped with an economizer

Back 3

provide "free cooling" on certain days of the year

Front 4

When installing an economizer it is important to check

Back 4

that the vanes do not bind during operation

Front 5

you just finished installing a 60,000 btuh output gas furnace and now you need to determine the volume of air that is flowing out of this furnace. you measure the supply temperature to be 105 F and the return temperature to be 68 F. What is the CFM at the bonnet

Back 5

1500 CFM

Front 6

The sensible heat equation can be used to determine air flow in which of the following systems

Back 6

fossil fuel heating

Front 7

where will your temperature probes be located for a delta T?

Back 7

2 and 4

Front 8

a manufacturer recommends a temperature rise between 35F and 55F. You have a temperature rise of 60F. How should you resolve this?

Back 8

increase the blower speed

Front 9

what could cause a higher than recommended temperature rise over a furnace

Back 9

a clogged air filter

Front 10

once a gas piping system has been assembled it should be pressure tested with

Back 10

compressed air

Front 11

a piping system that is pressurized with natural gas should be leak tested with

Back 11

an electronic leak detector and/or soap bubbles

Front 12

electronic leak detectors are calibrated in

Back 12

ppm

Front 13

what type of soap solution should be used to check for gas leaks?

Back 13

one specifically designed for that purpose

Front 14

which of the following is a diaphragm type differential pressure gage

Back 14

magnehelic

Front 15

a differential pressure gage reads pressures that are

Back 15

differential or relative to atmosphere

Front 16

a high supply side static pressure is an indication of

Back 16

a clogged evaporator coil

Front 17

a high return side static pressure is an indication of

Back 17

a dirty air filter

Front 18

why do you cross break ductwork

Back 18

to add strength and rigidity

Front 19

a duct traverse yields

Back 19

the average CFM based on the average velocity multiplied by the square feet of duct

Front 20

a direct drive blower wheel with damaged or missing vanes can cause

Back 20

loss of air flow, motor damage and noise

Front 21

during a PM call on a gas furnace you find loose and corroded wires. What, if anything, should be done?

Back 21

retighten all loose wires and replacethe corroded portions of the wires

Front 22

when preparing to perform an air balancing procedure

Back 22

all volume dampers should be open, the blower should be adjusted to the desired speed, and the air filter should be cleaned or replaced

Front 23

which of the following should be included in an air balancing report

Back 23

supply, return, and total static pressure

Front 24

in a trunk and branch duct system, trunk velocity should be kept between

Back 24

700 to 900 fpm

Front 25

horizontal runs of flexible duct should be supported every

Back 25

5 feet

Front 26

minimum strap width for hanging flexible duct is

Back 26

1 1/2"

Front 27

maximum sag for horizontal runs of flexible duct is

Back 27

1/2" per foot

Front 28

ductwork installed in unconditioned spaces should be

Back 28

insulated

Front 29

ducts installed in damp crawl spaces should be

Back 29

wrapped with insulationand wrapped with a vapor barrier

Front 30

human comfort can be defined in terms of

Back 30

dry bulb temperature, relative humidity, and air velocity

Front 31

The proper manifold pressure for natural gas is

Back 31

3.2" to 3.8" of water column

Front 32

the proper manifold pressure for LP gas is

Back 32

11" to 13" of water column

Front 33

inlet pressure to a gas valve should never exceed

Back 33

14" of water column

Front 34

in a combination gas valve

Back 34

the pilot valve is in series with the main valve

Front 35

a two stage gas valve has?

Back 35

two pressure regulators and two main valves

Front 36

manometers used to measure gas pressure are calibrated in

Back 36

inches of water column

Front 37

when reading a u-tube manometer

Back 37

the columns are added

Front 38

one psig is equal to

Back 38

27.72" of water column and 2.3' hd.

Front 39

the older mechanical thermostats and the newer electronic thermostats

Back 39

are made to be compatible

Front 40

which of the following thermostat types can be programmed for a different time schedule each day of the week

Back 40

7 day programmable

Front 41

to choose the proper air cleaner for a given application you must know?

Back 41

the volume of return air

Front 42

which of the following would be used to delay the off time for a blower

Back 42

delay on break relay

Front 43

which of the following is a category I furnace?

Back 43

83% AFUE

Front 44

venting a two pipe condensing furnace through the roof requires a maximum separation of the two pipes of

Back 44

18"

Front 45

when horizontally venting a condensing gas furnace be sure to

Back 45

maintain a 12" separation between the inlet and the outlet of the two pipoes

Front 46

when venting a category IV furnace what is the minimum separation from the vent pipe discharge to a forced air inlet into the building

Back 46

3 feet

Front 47

relative to combustion air a confined space is defined as

Back 47

an area with less than 50 ft^3 of volume for each 1000 btuh of input for all appliances in that area

Front 48

what is the required volume of air to sustain combustion?

Back 48

50 ft^3 per 1000 btuh input

Front 49

combustion air can be supplied to a confined space by

Back 49

one opening within 12" of the floor and one opening within 12" of the ceiling

Front 50

in venting tables for category I furnaces the "Vent Height" can be defined as

Back 50

the distance from the outlet of the draft diverter to the chimney cap

Front 51

the primary heat exchanger is typically made of

Back 51

aluminized steel

Front 52

the secondary heat exchanger is typically made of

Back 52

stainless steel

Front 53

a counterflow furnace installed in a closet must be mounted on

Back 53

a combustible floor base

Front 54

what else is important with regard to a closet installation of a two pipe 90% furnace in a residence

Back 54

Noise transmission

Front 55

an attic installation of a horizontal gas furnace requires

Back 55

the use of a zero clearance furnace or a non-combustible mounting base

Front 56

on a call for heat with an induced draft furnace, which of the following is the next event in the sequence of operation

Back 56

draft inducer is energized

Front 57

on a no heat call you find the following: R to W is made, The inducer is running, no main burner. What is most likely the cause of these symptoms?

Back 57

A pressure switch stuck closed

Front 58

on a call for heat the integrated circuit board will check for which of the following before energizing the draft inducer?

Back 58

An open pressure switch

Front 59

what device proves that the inducer motor is running and that the venting system is not obstructed

Back 59

pressure switch

Front 60

on a call for heat, after the pressure switch closes the next event is

Back 60

HSI is energized

Front 61

on a call for heat, after the HSI is energized the next event is

Back 61

main burner circuit is energized

Front 62

on a call for heat, after the main burner is energized the next event is

Back 62

flame is proved

Front 63

on a call for heat, after the flame is proven the next event is

Back 63

blower motor is energized

Front 64

the products of complete combustion include

Back 64

co2, nitrogen, water vapor, and heat

Front 65

primary combustion air

Back 65

is mixed with the gas in the venturi before ignition

Front 66

secondary combustion air

Back 66

is supplied to the burner after ignition to sustain combustion

Front 67

too much primary air can cause

Back 67

the flame to lift off the burner

Front 68

which of the following produces a hard, noisy blue flame

Back 68

in-shot burner

Front 69

ribbon burners must be properly aligned

Back 69

to insure proper flame carry-over

Front 70

modern residential gas burners are made from

Back 70

sheet metal

Front 71

which ignition system is de-energized once the main burner flame is established

Back 71

interrupted

Front 72

the pilot flame must envelope how much of the thermocouple

Back 72

3/8" to 1/2"

Front 73

a thermopile generates

Back 73

750 DC mV

Front 74

the ACCA manual used to perform residential load calculations is

Back 74

Manual J

Front 75

AFUE can be calculated by

Back 75

useful output/input

Front 76

a large difference between the wet bulb and the dry bulb temperatures is an indication of

Back 76

low relative humidity

Front 77

which of the following is used to measure RH%

Back 77

sling psychrometer