Book 2 Chapter 7: Low Water Fuel Cut-offs & Feedwater Controls

Question 1

The air blower used in a forced warm-air furnace is usually driven by:
A) An electric motor geared directly to the blower
B) A small diesel engine via. V-belt connected to a pulley mounted on the blower shaft
C) A small internal combustion engine geared directly to the blower rotor
D) An electric motor via a V-belt connected to a fixed pulley mounted on the blower shaft

Answer 1

D) An electric motor via a V-belt connected to a fixed pulley mounted on the blower shaft

Question 2

Which of the following are types of air distribution systems?
A) Extended plenum
B) Perimeter loop
C) Perimeter radial
D) All of the above

Answer 2

D) All of the above

Question 3

To determine the tension in a blower’s driving belt, a force of about ______ should be applied.
A) 25N (5.6 pounds force)
B) 30N (6.7 pounds force)
C) 45N (10 pounds force)
D) 75N (17 pounds force)

Answer 3

C) 45N (10 pounds force)

Question 4

If the warm air supply temperature is more than ________ higher than the return air temperature, the air filters are possibly plugged.
A) 25ºC (45ºF)
B) 38ºC (68ºF)
C) 50ºC (90ºF)
D) 65ºC (117ºF)

Answer 4

B) 38ºC (68ºF)

Question 5

Warm air furnace burners should be:
A) Adjusted often
B) Pressure tested often
C) Blown out regularly
D) Cleaned with a solvent regularly
E) Observed often for proper combustion

Answer 5

E) Observed often for proper combustion

Question 6

Dirty warm air furnace filters result in:
A) Low filter efficiency
B) Low heat exchanger temperature
C) Poor heating efficiency
D) High motor energy consumption
E) Low filter differential pressure

Answer 6

C) Poor heating efficiency

Question 7

One common cause for warm air furnace heat exchange failure is:
A) Crack on welded joints
B) The holes in the fresh air duct
C) Cold air leaking into the building
D) Too much air entering the furnace
E) Dry air entering the furnace

Answer 7

A) Crack on welded joints

Question 8

A fan belt should be replaced:
A) When it shows signs of fraying, cracking or wear
B) According to manufacturer’s recommendations
C) At regular intervals
D) Before each heating season
E) When it breaks

Answer 8

A) When it shows signs of fraying, cracking or wear

Question 9

Heat exchangers in gas fired furnaces are made of:
A) Brass
B) Cast iron
C) Copper
D) Steel
E) Aluminum

Answer 9

D) Steel

Question 10

The greatest danger presented by a cracked heat exchanger on a warm air furnace is the possibility of:
A) Carbon dioxide entering the air stream
B) Carbon monoxide entering the air stream
C) Raw fuel in the air stream
D) Hydrogen sulphide entering the air stream
E) Ethane in the air stream

Answer 10

B) Carbon monoxide entering the air stream

Question 11

Regular warm air furnace blower maintenance should include:
A) Shaft replacement
B) Casing replacement
C) Cleaning, lubrication and visual inspection
D) Bearing replacement
E) Pulley replacement

Answer 11

C) Cleaning, lubrication and visual inspection

Question 12

The perimeter loop system of a furnace ducting is ideal for a building with:
A) No insulation in the walls
B) No basement
C) No cold air returns
D) Concrete walls
E) Low head room in the basement

Answer 12

B) No basement

Question 13

A humidifier is usually installed in the:
A) Outside air vent
B) Fuel gas inlet
C) Heat exchanger
D) Warm air plenum
E) Combustion air inlet

Answer 13

D) Warm air plenum

Question 14

The low water fuel cut-off float is commonly used to operate both the Low water fuel cut-off switch and the:
A) Feedwater control switch
B) High steam pressure switch
C) Low feedwater temperature alarm
D) Low steam pressure alarm
E) Low fuel gas pressure switch

Answer 14

A) Feedwater control switch

Question 15

A second source of feedwater may be controlled by the:
A) Boiler operating control
B) Feedwater control switch
C) Boiler drum level control
D) Low water fuel cut-off device
E) Automatic blowdown device

Answer 15

D) Low water fuel cut-off device

Question 16

Possible causes of low water level include:
1. Leaks caused by breakage or corrosion
2. Excessive blowdown
3. Automatic feedwater valve passing
4. Boiler feed pump failure
5. Excessive makeup

A) 2,3,5
B) 1,2,4
C) 2,3,4
D) 1,2,3
E) 3,4,5

Answer 16

B) 1,2,4

Question 17

Make-up water for the heating system usually comes from the:
A) Deaerator
B) Returning condensate
C) City water supply
D) Boiler feedwater
E) Boiler feedwater pump

Answer 17

C) City water

Question 18

The float in the low water fuel cut-off will activate:
A) An electrical relay
B) An electrical switch
C) A gate valve
D) A solenoid valve
E) A globe valve

Answer 18

B) An electrical switch

Question 19

Low water fuel cut-off devices require regular attention, the following intervals are recommended:
1. Once per shift
2. Daily
3. Weekly
4. Month;y
5. No attention is required

A) 2,3,4
B) 3,4,5
C) 1,2,3
D) 2,3,5
E) 1,2,4

Answer 19

A) 2,3,4

Question 20

In a building heating system the condensate in the condensate receiver tank comes from the:
A) Make-up water supply
B) Boiler feedwater
C) Heating system
D) Economizer
E) Deaerator

Answer 20

C) Heating system

Question 21

The float operated low water fuel cut-off works on the principle of:
A) Differential pressure
B) Drum level variation
C) Temperature change
D) Buoyancy
E) Steam density

Answer 21

D) Buoyancy

Question 22

The main cause of heating boiler failure is overheating of the heating surfaces due to:
A) High firing rates
B) Low steam conditions
C) Scale build-up
D) High water conditions
E) Low water conditions

Answer 22

E) Low water conditions

Question 23

At normal boiler steaming rates, a condensate receiver tank should contain a sufficient volume of water equivalent to the water evaporated by the boiler for a maximum period of _____ minutes.
A) 45
B) 20
C) 60
D) 15
E) 30

Answer 23

E) 30