22
■ Timing hot water supply system
Centralized hot water supply system designed hourly hot water supply amount for where need timing
supply of hot water, such asresidence, hotels, hospitals, rest quarters of industrial enterprises, public
bathrooms, schools, theatres, gyms (stadiums) and other types of buildings:
1000
0
∑
=
′
b
N
q
G
h
h
Formula (4)
Formula (5)
Formula (6)
Formula (7)
G
h
’ — designed hot water supply amount per hour (m
3
/h);
q
h
— Hourly hot water use quota of sanitary ware (L/h), see Appendix II;
N
0
— Quantity of sanitary ware of the same type;
b — Use percentage of sanitary ware: 70%~100% for bath tubs or showers in bathrooms of residence,
hotels, hospitals and nursing home wards; 100% for showers and washbasins in bathrooms of industrial
enterprises’ rest quarters, public bathrooms, schools, theatres, gyms (stadiums), etc.
In formula (4), designed hot water supply amount per hour for all kinds of sanitary ware is calculated at
water temperature of 60ºC according to Appendix ll (refer to "Code for Design of Building Water Supply and
Drainage").
Then, all-day hot water consumption should be:
In formula (5) and formula (6):
t — water using temperature (ºC), see table 4-2;
T — total time for hot water supply every day (h).
N — Quantity the unit;
G
r
— all-day hot water consumption (m
3
);
g
j
— Producing water volume of a single unit (m
3
/h);
T
0
— designed operation time of the unit (h).
Since the capacity of the unit will be affected by ambient temperature changing along seasons, the balance
between the unit and the auxiliary heat source as well as the economic performance should be considered for
unit selection. If the unit is selected based on working conditions in summer, large auxiliary heat source will
be required in winter, which will lead to high operation cost; if the unit is selected based on working conditions
in winter, the capacity of the unit will be too large in summer and the initial investment in heat pump unit will
be quite large. It is necessary to find the economic balance point and design a hot water system with low
investment (including auxiliary heat source for the heat pump hot water unit) and low operation cost. When
determine the water volume, it is recommended to take the local annual average temperature as the ambient
temperature and the designed operation time of the unit T
0
is recommenced to be set at 10~14. Without
configuring of auxiliary heat source, the unit operation time is considered as 18 hours. The producing water
volume of the unit is taken as under the worst local conditions.
Based on the calculated all-day hot water consumption, unit model and quantity can be determined according
to the unit's producing water volume, at most 16 sets of unit of the same model can be combined. Producing
water volume of the unit is specified in “Unit Producing Water volume Variation Table” in the User Manual
where the producing water volume is for the situation with the final water temperature of 55ºC. For inlet water
temperature, please refer to local cold water temperature (see Appendix lll).
l
r
l
h
h
t
t
t
t
G
G
−
−
′
=
T
G
T
t
t
t
t
G
G
h
l
r
l
h
r
=
−
−
′
=
Unit selection calculation
0
T
g
G
N
j
r
×
=
