BCIT 5th class boiler engineer quiz 5 Flashcards
Building ventilation mechanical air filters can be divided into two broad classes, namely
a) viscous and electronic.
b) electronic and dry.
c) viscous and non-viscous.
d) dry and wet.
e) throwaway and renewable.
e) throwaway and renewable.
B02 CH08 Q006
Mechanical air filters for industrial applications can be divided into two broad classes.
Throwaway filters, which use a filtering medium cheap enough to be disposed of when it becomes dust laden.
Cleanable or renewable filters, which can be cleaned and reused. They can also be classified as dry filters or viscous filters, or they can be grouped according to the various shapes and sizes, filtering efficiencies, materials, etc.
The best filter for the removal of fine dust, smoke and fumes is the
a) air washer.
b) bag filter.
c) viscous filter.
d) electrostatic filter.
e) activated carbon filter.
d) electrostatic filter.
B02 CH08 Q008
The electrostatic filter is the best filter available for the removal of fine dust, smoke, and fumes and, therefore, is extensively used in buildings where the air supply has to be as clean as possible, as in hospitals. However, since this filter is much more expensive than other types of filters, its use for comfort air conditioning in buildings used for ordinary purposes, such as offices and apartments, is only limited.
The substances in the air stream that can be sterilized by ultraviolet light are
a) lint and dust.
b) pollen and smoke.
c) dust and pollen.
d) bacteria and spores.
e) mists and fogs.
d) bacteria and spores.
B02 CH08 Q010
In buildings where it is necessary to provide an atmosphere free of bacteria and mould spores, the air is often sterilized by the use of germicidal lamps. These lamps emit ultraviolet light which effectively destroys bacteria and spores in the air.
In a tubular-cased wire heating element, the compound surrounding the wire is
a) calcium hydroxide.
b) magnesium oxide.
c) aluminium oxide.
d) potassium permanganate.
e) calcium chloride.
B) magnesium oxide.
B02 CH09 Q010
One common type of elements used is tubular-cased wire. The nickel-chromium resistance wire is surrounded by magnesium oxide powder; wire and powder are enclosed in a heat and corrosion resistant steel tube. This design protects against electrical shock.
The advantages of an electric heating system over other heating systems include:
1. Relatively safe because no toxic gases are produced.
2. The capital cost and maintenance are usually lower.
3. Individual room temperature control is not required.
4. Lower operating cost.
5. Heater operation is clean and silent.
a) 1, 2, 3, 4 and 5.
b) 1, 3 and 4 only.
c) 3, 4 and 5 only.
d) 1, 2 and 5 only.
e) 2, 4 and 5 only.
d) 1, 2 and 5 only.
B02 CH09 Q008
Electricity is an ideal source of heat for homes, stores, apartments, etc., and its use has many advantages over other heating systems. Some of these advantages are:
- The absence of combustion and combustion gases. This means that electric heating devices produce no toxic gases and require no combustion air, no chimney, and no fuel storage. Also the absence of flame and, in most instances, the lower operating temperatures make the system quite safe.
- The equipment normally requires less space. A central system is usually not required, each room can be equipped with a separate heating unit.
- Individual room temperature control is easily obtained.
- The cost of installation is usually lower.
- The operation of the heating devices is clean and silent.
- Maintenance cost is lower.
The type of infrared heater that generates heat by the oxidation of fuel gas is a
a) direct-fired unit heater.
b) surface combustion heater.
c) internal fired heater.
d) low temperature catalytic heater.
e) electric infrared heater.
d) low temperature catalytic heater.
B02 CH09 Q006
Low Temperature Catalytic Heater contains a layer of glass wool impregnated with a catalyst, usually a metallic salt which promotes oxidation, backed up by a layer of porous refractory and covered by a metal screen. The gas-air mixture passes through the refractory into the layer of glass wool and catalyst. Oxidation of the gas takes place here. Oxidation causes the fuel to burn slowly without flame and the resulting temperature is considerably lower than in the normal combustion process. The heat produced is absorbed by the metal screen which then becomes the radiating surface.
To protect the electric element in a pan type of humidifier, the system should be equipped with
a) a low water level electric power cut off.
b) a high water level electric power cut off.
c) a high water temperature electric power cut off.
d) a ground fault interrupter.
e) a circuit breaker.
a) a low water level electric power cut off.
B02 CH10 Q016
The electrically heated pan humidifier is equipped with a low water cutoff switch to protect the element.
Identify the spray water temperature control method that is NOT used on an air washer.
a) Recirculating the spray water through a heat exchanger which can be either heated or cooled.
b) Varying the spray water header pressure to change the boiling temperature of the spray water.
c) Mixing part of the spray water with make up hot or cold water.
d) Heating or cooling the spray water by an immersed heating or cooling coil in the spray water sump.
b) Varying the spray water header pressure to change the boiling temperature of the spray water.
B02 CH10 Q014
To maintain the spray water at the desired temperature, the following methods are employed.
- Only part of the spray water is recirculated and hot or cold water is added as needed.
- The spray water is recirculated through a heat exchanger and is either heated or cooled by hot or chilled water. This method is illustrated in Fig. 3. A heating or cooling coil is directly mounted in the sump of the washer.
The humidifier that uses a fine water spray into air ducts to increase humidity is the
a) power type wetted element humidifier.
b) atomizing humidifier.
c) bypass type wetted element humidifier.
d) pan type humidifier.
e) pan type humidifier with plates.
b) atomizing humidifier.
B02 CH10 Q010
Atomizing Humidifier: In this type of humidifier water is broken up into small particles by using either a spinning disc or cone, or a spray nozzle. In the basic spinning disc type humidifier, a rapidly rotating disc atomizes the water into a fine mist. This unit is usually used as a room unit, either portable or stationary.
Industrial air washers should be installed at the
a) suction side of the supply air fan.
b) discharge side of the return fan.
c) suction side of the return fan.
d) discharge side of the supply air fan.
e) location where it can be most easily serviced.
a) suction side of the supply air fan.
B02 CH10 Q012
An air washer should be installed on the suction side of the fan where it can be maintained at a pressure slightly below that of the atmosphere in order to avoid leakage of water through the joints.
An example of a controlled device would be
a) a damper motor operating air louvers.
b) a thermostat.
c) a radiator.
d) a hot water boiler.
e) a steam boiler.
a) a damper motor operating air louvers.
B02 CH11 Q006
Controlled Devices: Many different types of controlled devices can be used to perform a certain function in response to the signal of the controller. For example, an electric thermostat may control:
- The fuel valve in the supply line to the burner of a furnace or boiler.
- An electric relay that switches the circulator in a hydronic system on or off.
- An electric radiator valve in the supply line to one or more steam or hot water convectors.
- A three-way mixing valve controlling the temperature of the water supply to a heating system.
- A three-way diverter valve controlling the water flow to a heating system.
- A damper motor operating air louvres.
A room thermostat should be mounted on an inside wall about
a) 1.0 m above the floor.
b) 1.5 m above the floor.
c) 1.25 m above the floor.
d) 0.5 m above the floor.
e) 0.75 m above the floor.
b) 1.5 m above the floor.
B02 CH11 Q010
Location of Room Thermostats: It is vitally important that the room thermostat be located in such a way that it can sense the average temperature of the area to be heated. It should always be mounted on an inside wall about 1.5 m above the floor, and in the path of natural air circulation when the heating system is off, but also in the path of the circulating air when the heating system is in operation.
In a basic electrical control system for a heating system, the device that senses a drop in air temperature is called the
a) pneumatic temperature sensor.
b) egualator.
c) humidistat.
d) thermostat.
e) final controlled device.
d) thermostat.
B02 CH11 Q008
Basic Electric Control System: To illustrate a basic electric control system we will use a typical warm air heating example. This system consists of a thermostat which controls the operation of the burner of a heating unit in the following sequence:
- The thermostat, which is the controller, senses a drop in air temperature (the controlled variable) below the set point temperature.
- The thermostat switch, which is the controller mechanism, closes to send an electric signal.
- The electric current is transmitted through an electric wire, which is called the connecting link, to the burner, also called the controlled device.
- The burner starts up, raising the temperature of the heat transfer medium, which in this case is air, and in turn transferring the heat to the air in the building.
- The thermostat senses the increase in air temperature.
- When the air temperature reaches the temperature setting of the thermostat, the switch opens and the burner shuts down.
On gas fired hot water heaters, “Aquastat” refers to a thermostatic device used to
a) regulates the hot water flow from the heater to the supply header.
b) proportion the air and fuel for correct combustion.
c) regulate the mixing of hot water and cooler water from the return and the make up cold water.
d) control the air flow to the heater.
e) control the fuel flow to the heater.
c) regulate the mixing of hot water and cooler water from the return and the make up cold water.
B02 CH12 Q014
A thermostatic controlling device, commonly called an “aquastat”, regulates the ratio of the two flows at the mixing valve so that the proper hot water temperature is maintained.
The backflow prevention method consisting of two check valves with a pressure differential relief valve between them is called
a) a PVB.
b) an air gap backflow prevention.
c) a double check valve.
d) an atmosphere vacuum breaker.
e) a reduced pressure principal device.
e) a reduced pressure principal device.
B02 CH12 Q020
Reduced Pressure Principal Device: This device is also known as an RP or RPP. It consists of two independently acting check valves with an automatic operating pressure differential relief valve located between the two check valves. The pressure between the two check valves is kept lower than the supply pressure by the first check valve. If for any reason either check valve leaks, the relief valve will discharge to atmosphere, maintaining the pressure in the area between the two check valves at lower than the supply pressure.
Characteristics of a circulating hot water system include:
- a return line connected near the end of each supply main.
- the length of the hot water line from the heater to the fixture is limited to 12.5 m.
- it wastes water.
- it eliminates hot water stagnation.
- circulation may be induced by gravity or by pumps.
a) 1, 2 and 3 only.
b) 1, 2, 4 and 5 only.
c) 1, 4 and 5 only.
d) 2, 4 and 5 only.
e) 2, 3 and 5 only.
c) 1, 4 and 5 only.
B02 CH12 Q012
Circulating Hot Water Systems: Circulating hot water systems have a return line connected near the end of each hot water main leading back to the water heater. This design eliminates hot water stagnation and allows hot water to be available at the fixture sooner and with much less waste of water than is the case in a non-recirculating system. This system can be applied to all types of buildings where the fixtures are a long distance from the central heating source. Circulation of hot water may be induced either by gravity or by the use of pumps. Many large, new buildings may have individual water heaters for every two to four floors so as to conserve energy by reducing heat losses in piping and energy consumption by large circulating pumps.
In an indirect hot water heater, the water is heated using
a) natural circulation.
b) gas or oil fired burners.
c) radiant heaters.
d) electric elements.
e) hot water or steam from the heating system.
e) hot water or steam from the heating system.
B02 CH12 Q016
Indirect Hot Water Heaters: Indirect hot water heaters are those which are heated by steam or high temperature water from a heating system. They may be of the storage or the instantaneous type.
To prevent hazardous conditions from occurring, a hot water heater will have
a) both a pressure and a temperature regulator installed.
b) a pressure regulator installed.
c) a temperature regulator installed.
d) a temperature regulator and a fusible plug installed.
e) pressure relief and temperature relief devices installed.
e) pressure relief and temperature relief devices installed.
B02 CH12 Q022
Hot water systems must be provided with safety devices to prevent dangerously high pressures and temperatures from developing in the system.
The most likely cause of water at the base of a faucet, even with the faucet closed is
a) a worn seat.
b) a worn washer.
c) corrosion in the valve body.
d) a worn packing.
e) a worn spout.
b) a worn washer.
B02 CH13 Q020
If a faucet drips when closed, or vibrates (“sings” or “flutters”) when opened, the trouble is usually a worn washer at the lower end of the spindle. If the faucet leaks around the spindle when opened, new packing is needed.
The storm drain piping installed in the building space should be
a) equipped with an automatic cleaning system.
b) electrically heat-traced.
c) equipped with gas traps.
d) insulated to prevent surface condensation.
e) constructed only of PVC.
d) insulated to prevent surface condensation.
B02 CH13 Q016
When storm drain piping is installed within a building, an insulating covering should be put on the pipes to prevent condensation on the outside surfaces of the piping during cold weather.
Water hammer in a plumbing system can be rectified by
1. the installation of air chambers.
2. closing valves slowly.
3. securing long lengths of pipe to joists or beams.
4. the use of over sized pipe.
5. installation of a strainer on the supply line.
a) 3, 4 and 5 only.
b) 1, 2 and 3 only.
c) 2, 3 and 4 only.
d) 1, 3 and 4 only.
e) 1, 2 and 5 only.
b) 1, 2 and 3 only.
B02 CH13 Q026
Water Hammer: This type of noise is a pounding or banging of pipes and shuddering of fixtures, caused by a shock wave that results when water flow in a pipe is suddenly stopped, perhaps by the rapid closing of a faucet. If allowed to continue, it can cause serious damage to a plumbing system, resulting in costly repairs. Other water hammer causes, however, are very difficult to locate. If necessary, short lengths of closed pipe may be installed in the plumbing system to form air chambers. These air chambers act as a “cushion” to absorb the excessive pressure caused in the system when a flow of water is suddenly stopped. If a system already has these air chambers, it may be that the air has leaked out. In that case, the water system must be drained and the air cushion restored. All exposed water pipes should be checked to ensure that there are no long lengths of pipe which are not fastened to a joist or beam with a pipe strap, pipe hanger, or similar fastening device. Providing support for these pipes might prevent the vibration which causes the noise.
Problems that may occur if plumbing vent piping is not properly sized and arranged include:
- sewer gas may enter the building.
- during cold weather, frost may plug the vent system.
- plumbing fixtures may drain slowly.
- traps may be siphoned out, breaking the liquid seals.
a) 1, 2, 3 and 4.
b) 2, 3 and 4 only.
c) 1 and 4 only.
d) 1 and 3 only.
e) 1, 2 and 3 only.
a) 1, 2, 3 and 4.
B02 CH13 Q012
Air Venting: It is very important to displace the air in the drainage system when wastes are being discharged. Positive pressure in the drainage system can force sewer gases back through the traps into the building. Negative pressure (partial vacuum) in the drainage system can allow the sealing liquid to be drawn out of the traps, thus breaking the seal between the drainage system and the building. A proper venting system prevents both of these undesirable conditions from occurring. In extremely cold climates, ice can accumulate inside the stack vent where it exits through the roof. Because of this, stack vents are usually oversized in buildings located in colder climates. During periods of cold weather, one should check for the build-up of ice in the venting system where it exits through the roof. Also note that a loop, connected to the stack above the point of waste discharge, provides a continuous supply of air to the horizontal branch line. This prevents siphoning of the sealing liquid out of upstream traps when downstream units are flushed.
Luminaires can be classified into the following types
a) recessed troffers, ceiling mounted wrap around, open reflectors and structural lighting.
b) incandescent, fluorescent and H.I.D.
c) manual, on/off, and automatic.
d) fluorescent, incandescent and sodium vapour.
e) general, local or supplementary, and combined general/local.
a) recessed troffers, ceiling mounted wrap around, open reflectors and structural lighting.
B02 CH14 Q002
1. Recessed Troffers: These are the most commonly used fluorescent luminaires for general lighting in offices and commercial interiors. The shielding and control is a prismatic panel (acrylic or glass) that provides an efficient light distribution. Because of the large number of luminaires required in a large installation, the system can sometimes appear excessively bright.
- Ceiling Mount Wraparounds: These have plastic enclosures that surround the lamp. They have a broad light distribution and are relatively cheap and efficient. They will appear too bright in many installations.
- Open Reflectors: These are typically used in industrial installations or in storage areas of commercial buildings. The reflectors serves as a shield to partially screen the lamps from view.
- Structural Lighting: Here lamps are fitted into coves, cornices, valances, and wall brackets that are architectural components of the room. Furthermore, desks and furniture may have built-in structural lighting to provide task lighting to supplement the ambient lighting. The use of special lenses, baffles, and louvres is an effective means of controlling excessive brightness. These reduce efficiency and usually add cost to the system; but the added comfort that is achieved may off-set the added costs.
Occupancy sensors are
a) all of the above.
b) modulating switches.
c) self-regulating switches.
d) automatic switches.
e) semi-automatic switches.
d) automatic switches.
B02 CH14 Q008
Occupancy Sensors: Occupancy sensors are being used in large buildings to reduce electrical bills by turning lights on when people enter a room and turning lights off when they leave. Employing occupancy sensors to turn lights on and off in areas of low occupation can reduce lighting costs by 20 to 60 percent. With these savings, the sensors can pay for themselves in less than two years. Sensor lighting control is most effective in spaces where there are transient types of activities and lights are easily forgotten. Some of these areas include conference and meeting rooms, hallways, washrooms, storage rooms and warehouses. Occupancy sensors are automatic switching devices that sense motion.
An advantage to low voltage switching for lighting control is
a) fewer switches are required.
b) less electrical power is used by the lighting.
c) better control of shadows is provided.
d) alteration work is simple and economical.
e) less heat is generated by the lighting.
d) alteration work is simple and economical.
B02 CH14 Q006
Low-Voltage Switching: The previous discussion on switches dealt with full voltage switches. This means that the switches are placed directly in the line to interrupt the circuit supplying current to the lights. The advantages of this system are:
- Local and remote control of lights is permitted, thus permitting centralization of control points and an increase in flexibility.
- The switching circuits are low voltage (24 V); therefore control wires without conduit can be used, greatly reducing costs.
- The full voltage circuitry is shortened, running only between the lights and the relays, thus reducing the quantities of expensive wiring required.
- Alteration work is simple and economical.
In a mechanical air intake natural exhaust ventilation system, the pressure in the building is
a) slightly above atmospheric pressure.
b) well below atmospheric pressure.
c) slightly below atmospheric pressure.
d) well above atmospheric pressure.
e) at atmospheric pressure.
a) slightly above atmospheric pressure.
B02 CH08 Q004
Mechanical Air Intake, Natural Exhaust:
Fresh air is forced into the building by a fan or blower moving the stale air out through the windows or air outlets in outside walls or the roof. This system keeps the pressure in the building slightly higher than atmospheric pressure and so prevents infiltration.
The substances in the air stream that can be sterilized by ultraviolet light are
a) mists and fogs.
b) pollen and smoke.
c) lint and dust.
d) bacteria and spores.
e) dust and pollen.
d) bacteria and spores.
B02 CH08 Q010
In buildings where it is necessary to provide an atmosphere free of bacteria and mould spores, the air is often sterilized by the use of germicidal lamps. These lamps emit ultraviolet light which effectively destroys bacteria and spores in the air.
The best filter for the removal of fine dust, smoke and fumes is the
a) electrostatic filter.
b) viscous filter.
c) bag filter.
d) activated carbon filter.
e) air washer.
a) electrostatic filter.
B02 CH08 Q008
The electrostatic filter is the best filter available for the removal of fine dust, smoke, and fumes and, therefore, is extensively used in buildings where the air supply has to be as clean as possible, as in hospitals. However, since this filter is much more expensive than other types of filters, its use for comfort air conditioning in buildings used for ordinary purposes, such as offices and apartments, is only limited.
A low temperature catalytic heater contains a layer of
a) glass wool impregnated with a catalyst.
b) plastic fibre impregnated with a catalyst.
c) porous glass impregnated with a catalyst.
d) metal impregnated with a catalyst.
e) wool fibre impregnated with a catalyst.
a) glass wool impregnated with a catalyst
B02 CH09 Q014
Low Temperature Catalytic Heater contains a layer of glass wool impregnated with a catalyst, usually a metallic salt which promotes oxidation, backed up by a layer of porous refractory and covered by a metal screen.
In an electric snow melting unit, a thermostat should be used to automatically shut the system down when the outdoor temperature is above
a) 1° C.
b) 0° C.
c) 2° C.
d) 3° C.
e) -1° C.
c) 2° C.
B02 CH09 Q012
The operation of an electric snow melting system can be controlled either manually with a pilot light indicating when the power is on, or automatically by a snow detector. In either case, an outdoor thermostat should be incorporated in the control system to protect the system from accidental operation during warm weather, by turning the system off when outdoor ambient temperature rises above 2°C (35.5°F).
In a tubular-cased wire heating element, the compound surrounding the wire is
a) calcium chloride.
b) potassium permanganate.
c) magnesium oxide.
d) aluminium oxide.
e) calcium hydroxide.
c) magnesium oxide.
B02 CH09 Q010
One common type of elements used is tubular-cased wire. The nickel-chromium resistance wire is surrounded by magnesium oxide powder; wire and powder are enclosed in a heat and corrosion resistant steel tube. This design protects against electrical shock.
Humidifying units that employ a small fan to draw warmer air from the furnace return air plenum or from the room, and force the air through a wetted pad and return the air to the room are called
a) regenerative type humidifiers.
b) atomizing type humidifiers.
c) by pass type humidifiers.
d) power type wetted element humidifiers.
e) pan type humidifiers with plates.
d) power type wetted element humidifiers.
B02 CH10 Q008
Power type units have a small fan to draw warm air from the furnace plenum or from the room, force it through the wetted pad, and return the humidified air to the plenum or the room.
When the outdoor temperature falls to below -25°C, the recommended relative humidity inside a home should be maintained at
a) greater than 30%.
b) greater than 50%.
c) less than 10%.
d) at a much greater value from where condensation starts to appear on window glass.
e) a slightly lesser value from where condensation starts to appear on window glass.
e) a slightly lesser value from where condensation starts to appear on window glass.
B02 CH10 Q006
From a health standpoint, a humidity between 35% and 50% is desirable; however in colder climates this may create a condensation problem on the cool surfaces of walls, windows, and ceilings which could result in damage to the structure. A building operator can accept as a good rule of thumb that when a slight condensation appears in the corners of the window panes, the relative humidity inside the building has reached its maximum permissible value with relation to the outside temperature.
Identify the spray water temperature control method that is NOT used on an air washer.
a) Heating or cooling the spray water by an immersed heating or cooling coil in the spray water sump.
b) Varying the spray water header pressure to change the boiling temperature of the spray water.
c) Recirculating the spray water through a heat exchanger which can be either heated or cooled.
d) Mixing part of the spray water with make up hot or cold water.
b) Varying the spray water header pressure to change the boiling temperature of the spray water.
B02 CH10 Q014
To maintain the spray water at the desired temperature, the following methods are employed.
1. Only part of the spray water is recirculated and hot or cold water is added as needed.
2. The spray water is recirculated through a heat exchanger and is either heated or cooled by hot or chilled water. This method is illustrated in Fig.
3. A heating or cooling coil is directly mounted in the sump of the washer.
Industrial air washers should be installed at the
a) discharge side of the return fan.
b) location where it can be most easily serviced.
c) suction side of the supply air fan.
d) suction side of the return fan.
e) discharge side of the supply air fan.
c) suction side of the supply air fan.
B02 CH10 Q012
An air washer should be installed on the suction side of the fan where it can be maintained at a pressure slightly below that of the atmosphere in order to avoid leakage of water through the joints.
Pressure controllers can be divided into two classes, namely, high pressure and low pressure controllers.
True
False
True
B02 CH11 Q012
Pressure controllers can be divided into two classes according to the pressure range of the measured variable. High pressure controllers measure and control high pressures or vacuums measured in kPa or in mm of mercury (e.g. steam or water pressures in an air conditioning system). Low pressure controllers measure and control low pressures and vacuums measured in mm of water (e.g. pressure in an air duct).
An example of a controlled device would be
a) a hot water boiler.
b) a radiator.
c) a damper motor operating air louvers.
d) a thermostat.
e) a steam boiler.
c) a damper motor operating air louvers.
B02 CH11 Q006
Controlled Devices: Many different types of controlled devices can be used to perform a certain function in response to the signal of the controller. For example, an electric thermostat may control:
- The fuel valve in the supply line to the burner of a furnace or boiler.
- An electric relay that switches the circulator in a hydronic system on or off.
- An electric radiator valve in the supply line to one or more steam or hot water convectors.
- A three-way mixing valve controlling the temperature of the water supply to a heating system.
- A three-way diverter valve controlling the water flow to a heating system.
- A damper motor operating air louvres.
A room thermostat should be mounted on an inside wall about
a) 1.5 m above the floor.
b) 0.75 m above the floor.
c) 1.25 m above the floor.
d) 1.0 m above the floor.
e) 0.5 m above the floor.
a) 1.5 m above the floor.
B02 CH11 Q010
Location of Room Thermostats: It is vitally important that the room thermostat be located in such a way that it can sense the average temperature of the area to be heated. It should always be mounted on an inside wall about 1.5 m above the floor, and in the path of natural air circulation when the heating system is off, but also in the path of the circulating air when the heating system is in operation.
The element that is NOT found in a circulating hot water system is
a) plugs.
b) back flow valves.
c) automatic air vents.
d) return piping.
e) heaters.
a) plugs.
B02 CH12 Q024
Circulating Hot Water Systems: Any hot water system consists of a heater, with or without a storage tank, supply piping to carry the hot water to the fixtures, and return piping to return the unused water back to the heater. A simple system with a storage tank is illustrated in Fig. Circulation is maintained because the water in the return main is cooler and more dense, therefore, exerting a greater pressure than the same height of water in the hotter supply main. A check or backflow valve must be installed in the return line so that no colder water can enter the hot water lines when there is maximum flow from the fixtures at end of the hot water supply. Cold water from a municipal distribution system or a domestic storage tank is used to supply the water heater. In many large hot water systems, it is impossible to develop adequate circulation by means of gravity. Pumps are used to improve circulation in both high and low buildings. A pump keeps the hot water circulating through the system and back to the heater. Automatic air vents are usually located at the top of hot water risers to remove air that is released when water is heated. If the hot water riser ends below the top floor fixtures, the top floor fixtures may be used to vent air from the system.
Most building regulations limit the length of a single pipe system from a water heater to
a) 30.2 m.
b) 6.0 m.
c) 15.2 m.
d) 12.5 m.
e) 20.5 m.
a) 30.2 m.
B02 CH12 Q010
Domestic Hot Water Distribution System: The single piping system is used to convey hot water from the water heater to the plumbing fixtures found in the building. Since the hot water is dead-ended at each fixture, it drops in temperature when the fixtures are not used for long periods of time. Thus, a large amount of water must be wasted before hot water becomes available at each fixture. Most plumbing regulations prohibit single pipe systems over 30 meters (100 feet) in length from a water heater.
A cross connection is any actual or potential connection between
a) the potable water supply and any source of other fluid.
b) the municipal water supply and the building water supply.
c) the soil water discharge and the waste water discharge.
d) the heating water system and the chilled water system.
e) the hot water supply and the cold water supply.
a) the potable water supply and any source of other fluid.
B02 CH12 Q018
Backflow Prevention
Backflow can be defined as a backwards flow of water or other liquid, gas, mixture, or other substance into the distributing pipes of a potable water supply from any source or sources. Backflow is caused by back syphoning which is caused by a negative or sub-atmospheric pressure in the line and by back pressure which is caused by a downstream pressure in the piping system that is higher than the upstream or supply pressure. Cross connection is any actual or potential connection between the potable water supply and any other source or system through which it is possible to introduce into the potable water system any used water, industrial fluid, gas, or other substance other than potable water. Any temporary or permanent device through which a backflow can or may occur is considered to be a cross connection.
To prevent hazardous conditions from occurring, a hot water heater will have
a) pressure relief and temperature relief devices installed.
b) a temperature regulator and a fusible plug installed.
c) a temperature regulator installed.
d) a pressure regulator installed.
e) both a pressure and a temperature regulator installed.
a) pressure relief and temperature relief devices installed.
B02 CH12 Q022
Hot water systems must be provided with safety devices to prevent dangerously high pressures and temperatures from developing in the system.
On gas fired hot water heaters, “Aquastat” refers to a thermostatic device used to
a) control the fuel flow to the heater.
b) control the air flow to the heater.
c) proportion the air and fuel for correct combustion.
d) regulate the mixing of hot water and cooler water from the return and the make up cold water.
e) regulates the hot water flow from the heater to the supply header.
d) regulate the mixing of hot water and cooler water from the return and the make up cold water.
B02 CH12 Q014
A thermostatic controlling device, commonly called an “aquastat”, regulates the ratio of the two flows at the mixing valve so that the proper hot water temperature is maintained.
The function of a water faucet is similar to a
a) gate valve.
b) stop and check valve.
c) butterfly valve.
d) flush valve.
e) globe valve.
e) globe valve.
B02 CH13 Q022
Water faucets and globe valves serve the same purpose; they control the flow of water. Faucets are used at discharge points over fixtures such as sinks, lavatories and tubs, while valves are used to close off portions of the plumbing system.
Which of the following statements about building drainage systems is TRUE?
a) Branch line connections to the waste stack should be connected at an angle greater than 45°.
b) Discharge horizontally through the outside walls.
c) The stack vent and loop vents allow equalization of pressure in the system.
d) On loop vent piping, slope is not important.
e) The stack vent prevents sewer gas from being vented through the roof.
c) The stack vent and loop vents allow equalization of pressure in the system.
B02 CH13 Q010
Normally, the vent stack is connected to the discharge stack at the house drain and at least every ten floors in a multi-story building, so as to equalize pressures and prevent negative or positive pressures from developing. Most buildings have several waste and soil stacks, with each waste stack providing drainage for only one section of the building.
The kind of pump usually used to lift the sewage from the sump in a building is a submersible
a) reciprocating pump.
b) centrifugal pump.
c) gear pump.
d) vacuum pump.
e) injector.
b) centrifugal pump.
B02 CH13 Q014
Submersible-type centrifugal pumps are often used for raising sewage to a higher level.
The cause of a continuously-running flushometer may be.
- the supply water pressure is too high.
- the bypass orifice is plugged.
- dirt is caught between the main valve seat or the auxiliary valve seat.
- an oversized by-pass orifice is in use.
a) 2, 3 and 4 only.
b) 2 and 3 only.
c) 1, 2, 3, and 4.
d) 1 and 2 only.
e) 1, 2 and 3 only.
b) 2 and 3 only.
B02 CH13 Q024
Valve continues to run.
A foreign object is resting on the auxiliary valve seat or the main valve seat.
Remove foreign objects from the seat. Check adjacent parts to make sure no scoring or pitting has occurred in the interim.
The bypass orifice is blocked.
Clean out the bypass orifice
Wearing or pitting has occurred on the auxiliary valve seat or the main valve seat.
Replace auxiliary valve seat washer or main valve seat (unless the seat is cast integrally, in which case nothing can be done).
Direct lighting systems
a) are more energy efficient than indirect lighting.
b) have greater glare control.
c) produce shadow free light.
d) blend with the environment.
e) have a higher initial cost than indirect lighting.
a) are more energy efficient than indirect lighting.
B02 CH14 Q004
Analysis of Direct Lighting
Advantages
- More energy efficient
- Low initial cost
- Low floor to ceiling height possible
- Easier to control and direct
Disadvantages
- Harsh Shadows
- Greater potential for direct glare
- Greater potential for veiling reflections and reflected glare
- Excessive luminance ratios on the ceiling
- Excessive luminance and glare causes a change in focal point to the ceiling
An advantage to low voltage switching for lighting control is
a) less electrical power is used by the lighting.
b) better control of shadows is provided.
c) less heat is generated by the lighting.
d) fewer switches are required.
e) alteration work is simple and economical.
e) alteration work is simple and economical.
B02 CH14 Q006
Low-Voltage Switching: The previous discussion on switches dealt with full voltage switches. This means that the switches are placed directly in the line to interrupt the circuit supplying current to the lights. The advantages of this system are:
1. Local and remote control of lights is permitted, thus permitting centralization of control points and an increase in flexibility.
2. The switching circuits are low voltage (24 V); therefore control wires without conduit can be used, greatly reducing costs.
3. The full voltage circuitry is shortened, running only between the lights and the relays, thus reducing the quantities of expensive wiring required.
4. Alteration work is simple and economical.
Occupancy sensors are
a) automatic switches.
b) semi-automatic switches.
c) all of the above.
d) modulating switches.
e) self-regulating switches.
a) automatic switches.
B02 CH14 Q008
Occupancy Sensors: Occupancy sensors are being used in large buildings to reduce electrical bills by turning lights on when people enter a room and turning lights off when they leave. Employing occupancy sensors to turn lights on and off in areas of low occupation can reduce lighting costs by 20 to 60 percent. With these savings, the sensors can pay for themselves in less than two years. Sensor lighting control is most effective in spaces where there are transient types of activities and lights are easily forgotten. Some of these areas include conference and meeting rooms, hallways, washrooms, storage rooms and warehouses. Occupancy sensors are automatic switching devices that sense motion.
