INSTALLATION, OPERATION AND MAINTENANCE MANUAL
BiSolid Saver OM-BSSV00/08/2012/EN
43
7. The overpressure in the expansion tank can be adjusted by exhausting until reaching the
value for hydraulic pressure of the system in cold condition. The exhausting has to be
performed by the valve, located on top of the expansion tank and the overpressure can
be measured with pressure-gauge in the hydraulic system. If adding water in the system
the pressure has to be regulated with maximum 10 kPa higher than the hydrostatic
height value of the system.
8. After filling the system with water it is recommended to mark the corrected hydrostatic
height value on the pressure-gauge with dashes and also the maximum pressure in the
system after reaching water temperature of 90
o
C.
9. If during operation values reach hydraulic difference between the marked dashes and
exceed minimum or maximum pressure, it is necessary to re-check the system, to air-
free it, add water when the system is in cold condition and eventually to correct the gas
pressure in the expansion tank, in compliance with the manufacture company directions.
10. In boilers which use expansion tanks the hydrostatic height value must be maximum 12
m.
11. Outer control checks of the expansion tanks and water inlet pressure must be performed
at least once per year.
12. Individual project must be designed for every heating system.
13. If optimum expansion tank is chosen then should not be measured more than 60 kPa
hydraulic pressure and within 10 to 90
o
C water temperature in the system. This
hydraulic difference can be checked by performing heat test in which the water in the
system has to be heated by starting from cold condition. If the measured hydraulic
difference is higher than 60 kPa this means that you have made wrong choice of
expansion tank and there is a risk of damaging the boiler.
Calculation of expansion tank volume:
Expansion tank volume: O = 1,3 . V . (P1+B)/B
B - hydraulic difference, with defined value at 50 kPa for steel made boilers
P1 - hydrostatic pressure in absolute value (kPa)
V - Increased water volume in the system…... V=G.v, (dm3)
1,3 – safety coefficient
G - mass of the water in the heating system, (kg)
v - water volume increase at defined temperature difference (dm
3
/kg)
t /°C/ 60 80 90
v /dm/kg/ 0.0224 0.0355 0.0431
The real hydraulic difference value can be higher than the calculated with maximum 10 kPa, in
case of calculated limiting values and increased gas pressure in the expansion tank, according
to point 7.
Example:
Mass of the water in the heating system
G = 180 kg
Hydrostatic height of the water in the heating system 9.5 m
Hydrostatic pressure absolute value
P1 = 195 kPa
Temperature difference in the system t = 80 °C
Change in the volume with t = 80 °C
v = 0.0355 dm
3
/kg
Safety valve corresponding overpressure
180 kPa
