ASPE CPD EVALUATION SETS ANSWERS AND
QUESTIONS SET A+
✔✔What effects do oversizing and undersizing have on a hot water circulating system?
- ✔✔Oversizing will cause additional money to be spent on materials and create
additional heat losses. Undersizing will seriously hamper circulation, thus preventing
adequate hot water from being immediately available to all the fixtures.
✔✔Since increased water temperatures can be damaging to pipes, what maximum hot
water velocity should be used to keep the hot water from eroding the pipe? - ✔✔6 fps
for copper pipe, similar fps for other types of pipe.
✔✔In lieu of a circulation system, what else can be done to maintain hot water
temperatures in piping? - ✔✔Use heat trace.
✔✔By what method does hot water supply piping (whether insulated or not) transfer
heat to surrounding lower-temperature air? - ✔✔Convection, conduction, and radiation.
✔✔Of the water stored in a storage hot water, what percentage is useable and why? -
✔✔70 percent, because the stored water is cooled by the entering cold water.
✔✔What is the primary reason for selecting a storage type water heater instead of
instantaneous? - ✔✔To smooth out peak demands on heating systems with large-
volume changes in hot water demand. When correct storage capacity is combined with
the correct recovery capacity and the proper size of heating medium control valve,
substantial reduction of the peak heating fluid demand can be realized.
✔✔Name three advantages of a booster water heater. - ✔✔1. Only as much water as is
required for the specific job needs to be heated to above normal system temperatures.
2. Savings in capital costs, maintenance, and operating costs are derived from the
limited use of very hot water. 3. Small boosters can be located near their jobs, with
simple controls, minimal waste, and smooth operation.
,✔✔What is a booster water heater? - ✔✔A water heater that serves to raise the
temperature of the regular hot water supply to some higher temperature needed to
perform special functions.
✔✔Describe a semi-instantaneous water heater (application, pros, etc.) - ✔✔A limited-
storage type heater that contains between 10 to 20 seconds of domestic water storage
according to its rated heating capacity. (A 60 gpm rated heater will have approximately
20 gal of water in its shell) This small quantity of water allows the temperature control
system to react to sudden fluctuations in water flow and to maintain the outlet water
temperature to within +/- 5 degrees F.
✔✔What are the sizing of instantaneous hot water heaters most commonly based on? -
✔✔Fixture units. Peak demand for hot water using this method is two to three times
actual demand, so it is recommended that usage factors be applied to select the most
economically sized instantaneous hot water heater.
✔✔Name one problem with instantaneous water heaters. - ✔✔Adequate control of the
temperature of the outlet water to within acceptable limits during fluctuating demand.
This fluctuation is called overshooting or undershooting.
✔✔The heat transfer rate increases or decreases when water velocity increases in the
tubes? - ✔✔increases.
✔✔What is the minimum velocity that should be maintained through the tubes on an
instantaneous water heater? - ✔✔4 fps. This will minimize the rate of scale formation in
the tubes.
✔✔How should the instantaneous water heater be configured if the characteristics of
water are such that rapid scale deposits are possible? - ✔✔A straight-tube, floating
head exchanger should be used in lieu of the U-tube heater.
✔✔What is the most common form of instantaneous water heater? - ✔✔The U-tube,
removable bundle exchanger with steam or boiler water in the shell and domestic water
flowing through the tubes.
✔✔What should always be provided with instantaneous water heaters? - ✔✔A hot
water temperature limit to prevent scalding water from entering the system. This is
becoming more standard regardless of the type of water heater used.
✔✔Describe Instantaneous Water Heaters (application, pros, etc.) - ✔✔No built in
storage, designed to deliver full capacity rapidly and continuously. Must have sufficient
capacity to meet all demands simultaneously. Require a high heat input to meet the
required discharge rate and temperature of hot water. Best applied where demands are
, level and constant, such as swimming pools, dishwasher boosters, industrial processes.
They heat the water through conduction.
✔✔When using a fuel fired water heater, you must always provide what? -
✔✔Combustion air
✔✔Describe Direct Fired Storage water heaters (application, pros, etc.) - ✔✔Simple,
inexpensive in installation, piping, controls. Used in homes, small commercial. Low
demand heaters with low btu inputs so the heating of the water is spread over several
hours.
✔✔What is a good standard hot water temperature and why? - ✔✔140F because it kills
legionella and other harmful bacteria
✔✔When selecting a hot water heater, what cold inlet and rise temperatures are
commonly used? - ✔✔40 degree cold inlet, 100 degree F rise
✔✔What is the first step in selecting a hot water heater? - ✔✔Knowing the required
capacity.
✔✔What can the pressure setting on the relief valve be set to? - ✔✔25-30 lbs higher
than the system operating pressure (or 125 psi) to avoid false opening and dripping due
to normal pressure surges. The pressure setting must be less than the maximum
working pressure of the materials in the system.
✔✔What may be installed to prevent explosions in hot water systems? - ✔✔A combined
(or separate) temperature and pressure relief valve. Overheating is the direct cause of
explosions, protection against excessive temperature and pressure is needed.
Temperature and pressure relief valves must have a relief capacity of not less than the
pressure or heat input at maximum operating capacity. Every relief valve should have a
discharge pipe connected to it’s outlet of at least the size of the valve discharge
outlet.
✔✔What is the working limit design pressure for standard plumbing equipment to
minimize the risk of explosion? - ✔✔125 psi.
✔✔List the five objectives for the design of an efficient hot water distribution system. -
✔✔Adequate amounts of hot water, safe performance, economical heat source, cost-
effective and durable installation, economical operating system with reasonable
maintenance.
✔✔Give an example of a centrifugal pump, an axial pump, and a positive-displacement
pump. - ✔✔An automobile water pump, a boat propeller, and the human heart
QUESTIONS SET A+
✔✔What effects do oversizing and undersizing have on a hot water circulating system?
- ✔✔Oversizing will cause additional money to be spent on materials and create
additional heat losses. Undersizing will seriously hamper circulation, thus preventing
adequate hot water from being immediately available to all the fixtures.
✔✔Since increased water temperatures can be damaging to pipes, what maximum hot
water velocity should be used to keep the hot water from eroding the pipe? - ✔✔6 fps
for copper pipe, similar fps for other types of pipe.
✔✔In lieu of a circulation system, what else can be done to maintain hot water
temperatures in piping? - ✔✔Use heat trace.
✔✔By what method does hot water supply piping (whether insulated or not) transfer
heat to surrounding lower-temperature air? - ✔✔Convection, conduction, and radiation.
✔✔Of the water stored in a storage hot water, what percentage is useable and why? -
✔✔70 percent, because the stored water is cooled by the entering cold water.
✔✔What is the primary reason for selecting a storage type water heater instead of
instantaneous? - ✔✔To smooth out peak demands on heating systems with large-
volume changes in hot water demand. When correct storage capacity is combined with
the correct recovery capacity and the proper size of heating medium control valve,
substantial reduction of the peak heating fluid demand can be realized.
✔✔Name three advantages of a booster water heater. - ✔✔1. Only as much water as is
required for the specific job needs to be heated to above normal system temperatures.
2. Savings in capital costs, maintenance, and operating costs are derived from the
limited use of very hot water. 3. Small boosters can be located near their jobs, with
simple controls, minimal waste, and smooth operation.
,✔✔What is a booster water heater? - ✔✔A water heater that serves to raise the
temperature of the regular hot water supply to some higher temperature needed to
perform special functions.
✔✔Describe a semi-instantaneous water heater (application, pros, etc.) - ✔✔A limited-
storage type heater that contains between 10 to 20 seconds of domestic water storage
according to its rated heating capacity. (A 60 gpm rated heater will have approximately
20 gal of water in its shell) This small quantity of water allows the temperature control
system to react to sudden fluctuations in water flow and to maintain the outlet water
temperature to within +/- 5 degrees F.
✔✔What are the sizing of instantaneous hot water heaters most commonly based on? -
✔✔Fixture units. Peak demand for hot water using this method is two to three times
actual demand, so it is recommended that usage factors be applied to select the most
economically sized instantaneous hot water heater.
✔✔Name one problem with instantaneous water heaters. - ✔✔Adequate control of the
temperature of the outlet water to within acceptable limits during fluctuating demand.
This fluctuation is called overshooting or undershooting.
✔✔The heat transfer rate increases or decreases when water velocity increases in the
tubes? - ✔✔increases.
✔✔What is the minimum velocity that should be maintained through the tubes on an
instantaneous water heater? - ✔✔4 fps. This will minimize the rate of scale formation in
the tubes.
✔✔How should the instantaneous water heater be configured if the characteristics of
water are such that rapid scale deposits are possible? - ✔✔A straight-tube, floating
head exchanger should be used in lieu of the U-tube heater.
✔✔What is the most common form of instantaneous water heater? - ✔✔The U-tube,
removable bundle exchanger with steam or boiler water in the shell and domestic water
flowing through the tubes.
✔✔What should always be provided with instantaneous water heaters? - ✔✔A hot
water temperature limit to prevent scalding water from entering the system. This is
becoming more standard regardless of the type of water heater used.
✔✔Describe Instantaneous Water Heaters (application, pros, etc.) - ✔✔No built in
storage, designed to deliver full capacity rapidly and continuously. Must have sufficient
capacity to meet all demands simultaneously. Require a high heat input to meet the
required discharge rate and temperature of hot water. Best applied where demands are
, level and constant, such as swimming pools, dishwasher boosters, industrial processes.
They heat the water through conduction.
✔✔When using a fuel fired water heater, you must always provide what? -
✔✔Combustion air
✔✔Describe Direct Fired Storage water heaters (application, pros, etc.) - ✔✔Simple,
inexpensive in installation, piping, controls. Used in homes, small commercial. Low
demand heaters with low btu inputs so the heating of the water is spread over several
hours.
✔✔What is a good standard hot water temperature and why? - ✔✔140F because it kills
legionella and other harmful bacteria
✔✔When selecting a hot water heater, what cold inlet and rise temperatures are
commonly used? - ✔✔40 degree cold inlet, 100 degree F rise
✔✔What is the first step in selecting a hot water heater? - ✔✔Knowing the required
capacity.
✔✔What can the pressure setting on the relief valve be set to? - ✔✔25-30 lbs higher
than the system operating pressure (or 125 psi) to avoid false opening and dripping due
to normal pressure surges. The pressure setting must be less than the maximum
working pressure of the materials in the system.
✔✔What may be installed to prevent explosions in hot water systems? - ✔✔A combined
(or separate) temperature and pressure relief valve. Overheating is the direct cause of
explosions, protection against excessive temperature and pressure is needed.
Temperature and pressure relief valves must have a relief capacity of not less than the
pressure or heat input at maximum operating capacity. Every relief valve should have a
discharge pipe connected to it’s outlet of at least the size of the valve discharge
outlet.
✔✔What is the working limit design pressure for standard plumbing equipment to
minimize the risk of explosion? - ✔✔125 psi.
✔✔List the five objectives for the design of an efficient hot water distribution system. -
✔✔Adequate amounts of hot water, safe performance, economical heat source, cost-
effective and durable installation, economical operating system with reasonable
maintenance.
✔✔Give an example of a centrifugal pump, an axial pump, and a positive-displacement
pump. - ✔✔An automobile water pump, a boat propeller, and the human heart
