Book 2 Chapter 7: Low Water Fuel Cut-offs & Feedwater Controls Flashcards
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
D) An electric motor via a V-belt connected to a fixed pulley mounted on the blower shaft
Which of the following are types of air distribution systems?
A) Extended plenum
B) Perimeter loop
C) Perimeter radial
D) All of the above
D) All of the above
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)
C) 45N (10 pounds force)
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)
B) 38ºC (68ºF)
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
E) Observed often for proper combustion
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
C) Poor heating efficiency
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
A) Crack on welded joints
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
A) When it shows signs of fraying, cracking or wear
Heat exchangers in gas fired furnaces are made of:
A) Brass
B) Cast iron
C) Copper
D) Steel
E) Aluminum
D) Steel
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
B) Carbon monoxide entering the air stream
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
C) Cleaning, lubrication and visual inspection
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
B) No basement
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
D) Warm air plenum
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
A) Feedwater control switch
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
D) Low water fuel cut-off device
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
B) 1,2,4
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
C) City water
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
B) An electrical switch
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
A) 2,3,4
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
C) Heating system
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
D) Buoyancy
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
E) Low water conditions
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
E) 30
