Appendix - Grundfos PHP A-1 4.0 Instruction Manual

PHP A-1 Instruction Manual / Appendix
12

Appendix

APPENDIX A - DIMENSIONING OF EXPANSION PIPES
Expansion pipes connect the plant with the expansion and
pressure maintenance device.
INFORMATION
To calculate the expansion pipe you need to know the
nominal power to be dissipated, the max. operating
temperature and the flow speed acc. to ÖNORM H
5151-1:2010 12 15.
Part out of ÖNORM H 5151-1:2010 12 15:
11.2.3.2 Dimensioning of the expansion pipe
When dimensioning the expansion pipe the following points
must be observed:
• The dimensioning of the expansion pipe is based on the
nominal power of the heat generator.
• In plants with a nominal power smaller than 500 kW the
minimum nominal diameters can be taken from table 6.
Table 6 - Minimum nominal diameters of expansion pipes
DN
20
20
• The max. flow rate within the expansion pipe must not
exceed 0,15 m/s.
NOTE
If the system is divided between heat supply and
heat distribution a lower water volume could exist within
the heat supply system. Therefore the dimensioning
of the expansion pipe based on the max. flow rate
can be necessary.
The calculation of the flow rate within the expansion pipe is
based on the percentage temperature-dependent increase
in volume V
from the filling temperature (10°C) to the safety
e
temperature and the total content V
TZ
49
Nominal power in kW
up to 120
from 120 to 500
of the system.
A
The heating time t which is necessary for reaching the
A
safety temperature of the total content of the system V
TZ
is calculated acc. to equation (22):
The expansion flow V is calculated acc. to equation (23):
e
The inside diameter of the expansion pipe is calculated acc.
to equation (24):
The next pipe dimension must be selected. The max.
pressure drop within the expansion pipe must not be bigger
than 1 kPa.
NOTE
At the inside of the pressure maintenance device
(overflow pipe, suction pipe) the manufacturer defines
the flow rates which ensure a trouble-free function of
the pressure maintenance device. According to this, the
max. flow rates are 0,75 m/s in the overflow pipe and
0,50 m/s in the suction pipe.
A