Opop H 635 Manual page 10

11) Each pressure expansion vessel shall be checked visually at least once a year. This check shall be
accompanied by the charge pressure check.
12) A project shall be worked out and approved for every heating system.
13) The pressure difference in correctly selected pressure expansion vessel shall not exceed 60 kPa at the
system water temperature of from 10 up to 90 °C. This pressure difference can be checked during heating
test, when the system water heats up from the cold condition. If the pressure difference is bigger than
60 kPa, the pressure expansion vessel has not been selected correctly and the pressure body may be
damaged.
Calculation:
(based on proposed amendment of Art. 122, CSN 06 0830)
Volume of the pressure expansion vessel:
P B
+
1
O V
= ×
B
Where:
B - Pressure difference determined for steel boilers at 50 kPa
P - Absolute value of the hydrostatic pressure (kPa)
1
V - Increased volume of water in the whole system (dm
V = G. ∆ v
Where:
G - Weight of water in the heating system (kg)
v - Increase of the specific value of water at certain temperature difference (dm . kg
°
C
∆ t
3
dm . kg
∆ v
The actual pressure difference can be higher than the calculated value by not more than 10 kPa. In case of
boundary calculated values and due to the gas pressure increase in the pressure expansion vessel by the
water pressure as per section 7.
Example:
Weight of water in the heating system
Hydrostatic height of water in the system
Temperature difference in the system
Volume change for ∆ v of 80 °C
Safety valve set to
Pressure difference
Waver volume increase in the whole system:
V = G x ∆ v
V = 180 x 0.0355
3
V = 6.39 dm
The minimum required volume of the expansion vessel:
P B
+
1
O' V
= ×
B
195
O' 6.39
= ×
Hot Water Boiler Manual – Models H 635, H 650
60 80
-1
0.0224 0.0355
50
+
3
33.311 dm
=
50
3
)
90
0.0431
G = 180 kg
9.5 m
P = 195 kPa
1
°
∆ v = 80 C
3 -1
∆ v = 0.0355 dm . kg
180 kPa
B = 50 kPa
10
-1
)