23
■ All-day hot water supply
Service capacity of the water tank V
water tank
(the total capacity under the higher water level is the service
capacity):
G
j
is the producing water volume of the unit under worst local conditions
■ Timing hot water supply system
Service capacity of the water tank V
water tank
(the total capacity under the higher water level is the service
capacity):
Gjis the producing water volume of the unit under worst local conditions
Thermal insulation must be applied for the water tank which should meet the following conditions:
1. Ensure that the temperature difference of the water tank in a day and night should be not more than 5ºC.
2. The design of thermal insulation structure should ensure good thermal insulation effect, convenient
construction, be fire-proofing, water-proofing, durable and beautiful.
3. Dismountable thermal insulations structure should be adopted at the access hole of the water tank.
4. Water tanks placed outdoors should be configured with protective layer which should have functions of
thermal insulation layer protection and water proofing. Metal protective layer is recommended, such as
galvanized steel sheet at 0.3~0.8mm thickness or enclosure made of anti-rust aluminum sheet. Prevent
rain water from entering at the joint of the shell by overlap joint technology.
Note: recommend the water tank capacity should be no less than 5 times of the water volume of the
ordinary type of unit; For northern area with cold weather, the capacity of the water tank should be
no less than the designed daily water consumption in principle.
According to the project's needs, a set of auxiliary electric heater can be installed as backup system
which will be started up during equipment maintenance period when a temporary failure occurs for the
equipment. Besides, the backup system can also make up capacity degradation of the unit when the ambient
temperature is extremely low so as to guarantee producing water volume of the unit.
Usually, the capacity of the auxiliary electric heater will be: W=a*Q
2
=a* (Q-Q
1
). (Where, a is the margin
coefficient with the value range of 1.0~1.5; the value of a should be higher in northern area; it may be 1.5 in
cold northern areas).
For area with outdoor ambient temperature in winter lower than -7ºC, it is recommended to configure auxiliary
heating equipment with heating capacity equivalent to the unit to ensure hot water supply when the heat
pump unit does not run. Cost for hot water production can be significantly reduced by hot water production by
heat pump water heater in summer and transition season, which has even better economic performance for
boiler reconstruction projects in northern areas.
Formula (8)
Formula (9)
Water tank selection calculation
Selection of auxiliary electric heater (Backup)
24
(
1
.
1
h
water tank
K
G
G
V
j
r
−
≥
( )
24
(
1
.
1
h
water tank
K
G
G
V
j
r
−
≥
( )
