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Level 3 - Gas Exam 3 > Forced-air furnaces w/s > Flashcards

Forced-air furnaces w/s Flashcards

1
Q

If the venting on a high efficiency furnace runs through unheated spaces, what must be done?

a) it must be insulated
b) it must be protected from damage
c) it must increased

A

a)

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2
Q

How would an installer determine the existing ductwork is adequately sized for the new high efficiency furnace?

a) complete a heat loss calculation
b) check the blower motor amp draw
c) perform an external static pressure test

A

c)

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3
Q

If an HRV is used in conjunction with a furnace, where is the HRVs warm air supply connected to the furnace system?

a) on the return air ducting but at least 3m from furnace
b) on supply air ducting but at least 3m from furnace
c) on the return air duct but no more than 3m from furnace

A

a)

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4
Q

If a furnace has air-conditioning added, where does the cased coil go?

a) downstream of the burner and downstream of the blower
b) upstream of the burner and upstream of the blower
c) downstream of the burner but upstream of the blower

A

a)

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5
Q

In what position can condensing furnaces be installed?

a) up or horizontal left only
b) up or horizontal left and right
c) up, down, horizontal left and right
d) only positions approved by the manufacturer

A

d)

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6
Q

What is the AFUE rating of a high-efficiency condensing furnace?

a) 83% or greater
b) greater than 83%
c) 90% or greater

A

c)

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7
Q

Which category of furnace is a high efficiency appliance?

a) category 1
b) category 2
c) category 3
d) category 4

A

d)

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8
Q

What type of furnaces use an inducer fan?

a) mid efficiency only
b) high efficiency only
c) mid efficiency, high efficiency

A

c)

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9
Q

Why is condensate considered corrosive?

a) it has low ph and low acidity
b) it has high ph and low acidity
c) high ph and high acidity
d) low ph and high acidity

A

d)

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10
Q

What is the draft pressure in the vent from a condensing furnace?

a) neutral
b) positive
c) negative
d) positive or negative depending on input

A

b)

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11
Q

How are type BH vents sized?

a) using furnace manufacturers literature
b) using vent pipe manufacturers literature
c) vent sizing tables

A

a)

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12
Q

When upgrading to a high efficiency furnace from a low efficiency model how is the appliance input decided?

a) complete a heat loss calculation
b) replace old trance with the same input
c) choose model that has the size size supply air plenum

A

a)

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13
Q

Can the vent from a condensing appliance be connected to the B-vent of the appliance it replaces?

a) no, a new vent needs to be installed
b) yes, if the existing vent is the correct size
c) yes, if the existing b vent is a side wall termination

A

a)

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14
Q

How is the bent piping graded for sidewall installation?

a) perfectly horizontal
b) toward the appliance
c) away from the appliance
d) to a low point

A

b)

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15
Q

Must a defective heat exchanger in a dwelling unit be replaced immediately?

a) yes
b) no, it can be temporarily repaired
c) no, it can be permanently repaired
d) no, only if CO level is above the maximum acceptable for the appliance

A

a) yes

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16
Q

A high efficiency furnace incorporates how many heat exchangers?

a) one
b) two, primary and a tertiary
c) two, primary and a secondary

A

c)

17
Q

When would a gas technician/fitter use an incline manometer?

a) to check the manifold pressure
b) to complete an external static pressure test
c) to confirm operation of the high-limit switch

A

b)

18
Q

What is the purpose of a flame rollout switch?

a) open in the event of a spillage
b) open when the combustion air is blocked
c) protect the burner area from unusually high temperature
d) protect heat exchanger

A

c)

19
Q

What is the purpose of a diaphragm-style pressure switch on a condensing furnace?

a) to confirm the gas pressure is correct
b) to confirm induced draft fan is operating
c) to confirm the blower assembly is operating

A

b)

20
Q

On what type of furnace could you see a combination high-limit/fan control?

a) low efficiency only
b) high efficiency only
c) low efficiency and mid efficiency
d) mid efficiency and high

A

c)

21
Q

What material is recommended for condensate piping after connecting to the appliance?

a) rigid pvc piping
b) flexible pvc tubing
c) any steel pipe material
d) any plastic pipe material

A

a)

22
Q

How is temperature rise determined?

a) ambient temp plus room air temp
b) add return air temp to supply air temp
c) subtract supply air temp from return air temp
d) subtract return air temp from supply air temp

A

d)

23
Q

What type of furnace would use a vent damper?

a) mid eff
b) low eff
c) low efficiency and mid efficiency
d) all types

A

a)

24
Q

What tool should be used to clean the outside of a heat exchanger?

a) soft brush
b) wire brush
c) sanding block

A

a)

25
Q

When is a condensate pump required?

a) all condensing appliance installations
b) when a condensate trap cannot be installed
c) when the condensate cannot drain by gravity to the DWV system

A

c)

26
Q

Where does condensate form in a condensing appliance system?

a) only in the primary heat exchanger
b) only in secondary heat exchanger
c) in primary an secondary heat exchangers
d) in the secondary heat exchanger and venting system,

A

d)

27
Q

How is manifold pressure measured on a residential furnace?

a) upstream of combination gas valve with appliance off
b) downstream of combination gas valve with appliance off
c) upstream of combination gas valve with appliance on
d) downstream of combination gas valve with appliance operating

A

d)

28
Q

Where is a combustion analysis performed?

a) in the combustion chamber
b) should be measured after any draft control devices
c) should be measured before nay draft control devices

A

c)

29
Q

Referencing a combination control, what is the approx normal differential setting of the fan control?

a) 25F
b) 35F
c) 45F
d) 55F

A

a)

30
Q

Referencing a mid efficiency furnace, what causes the fan to shut off under normal operating conditions?

a) pressure switch circuit opens
b) the IFC fan -off timer is activated
c) the fan control cools down enough to open the circuit

A

c)

31
Q

On which types of furans would you find an auxiliary limit control?

a) only central furnaces
b) down flow furnaces only
c) horizontal or down floe furnaces
d) upflow, horizontal, and down flow

A

c)

32
Q

Do all rollout switches have to be manually reset?

a) yes
b) no

A

b) no

33
Q

If the return air temperature is 70F and the temp rise is 75 F what is the supply temp?

a) 5F
b) 70F
c) 75F
d) 145 F

A

d)

34
Q

What component is designed to cause the burner to shut down if there is a blockage in the vent?

a) high limit
b) presuretrol
c) roll out switch
d) pressure switch

A

d)

35
Q

What would be the required air flow if a furnace has a rated input of 60,000 btu and is 95% efficiency and the rating plate specifies a temperature rise of 40-60F

a) 880CFM
b) 926CFM
c) 1056 CFM

A

c)

36
Q

What voltage does the IFC receive from the thermostat circuit on a call for heat?

a) 24 AC
b) 24v DC
c) 120v AC

A

a)

37
Q

How is the indoor blower circuit energized on a furnace incorporating an IFC?

a) the IFC uses electronic time delay
b) the IFC uses temperature-activated switch
c) the furnaces uses a separate fan control board

A

a)

38
Q

What is the range of a typical modulating furnace?

a) between 0% and 100% of input
b) between 40% and 100% of input
c) between 0% and 100% of capacity
d) between 40% and 100% of capacity

A

d)

39
Q

Why is it recommended to perform an ESP after retrofitting a furnace to existing ductwork?

a) to ensure the franc is operating within ESP limits
b) to ensure the furnace is operating within temp rise limits
c) to ensure the furnace is operating with temperature rise limits and ESP limits

A

c)

Level 3 - Gas Exam 3 (4 decks)

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