Closed Expansion Tanks are designed to meet the volumetric change of the heated water in heating systems, to keep the static pressure created by the pump at the usage level in sanitary applications, and to compensate for the changes in the water flow. A correctly selected expansion tank in the system prevents sudden pressure changes and prolongs the life of the installation elements and the pump.
TABLE: 1
TABLE: 2
TABLE: 3
CALCULATION OF THE AMOUNT OF CIRCULATION WATER IN THE SYSTEM
Vs : Q x f (liter)
Vs: Total amount of water in the system (lt)
Q: Heating capacity of the boiler (kCal/h)
f: Heat dissipation power of the heater (TABLE: 1)
Vg: Vs x n (liter)
Vg: The amount of water that the system will expand (lt)
n: Expansion coefficient of water according to temperature difference (TABLE: 2)
Vn: Vg ÷ K (liter)
Vn: Normal expansion tank volume (liter)
K: Coefficient according to pressure setting of safety valve with pre-pressure (TABLE: 3)
CONSTANT PRESSURE AND SAFETY VALVE ACCOUNT
Static Pressure: Building Floor Count x 2.8 m/floor + Boiler Room Height = Total Room Height ÷ 10 = Bar
Pre-Gas Pressure: Static Pressure + (0.2 ~ 0.5 bar is added.)
Safety Valve Pressure Value: Pvalve = Psafety – Ptolerance
Psa: OPERATING PRESSURE
Ptolerance: Psa ≤ 5 bar if 0.5 acceptable.
If; Ptolerance: Psa > 5 bar if Psa x 0.1 is taken.
SAMPLE ACCOUNT I
A panel radiator was used as a heating element in an apartment with 10 floors and 22 flats. 70/50 °C water circulates in the system. There is a boiler in the building with a heating power of 200,000 kCal/h. What is the pressure and volume of the expansion tank to be used in the system?
1) PRESSURE CLASS
Static Pressure: 10 x 2.8 + 3 ==> 31 ÷ 10 ≅ 3.1 bar
Front Gas Pressure: 3.1 + 0.4 = 3.5 bar
Psa: 5.5 bar (işletme basıncı)
Safety Pressure Value: 5.5 – 0.5 = 5 bar
2) NORMAL VOLUME OF WATER
Total Water Volume in the System:
Vs: Q x f, f: (to TABLE: 1)
Vs: 200.000 x 10 ÷ 1000 = 2000 liter
Expanded Water Volume in the System:
Vg: Vs x n, n: (to TABLE: 2)
n: 900 - 100 = 0.0359 – 0.00027 = 0.0356
Vg: 2000 x 0.0356 = 71.2 Liter
3) NORMAL VOLUME OF EXPANSION TANK
Vn : Vg ÷ K
K: ( By accepting the pre-gas pressure 3.5 bar and the safety valve pressure 5 bar (to TABLE: 3) K : 0.25 )
Vn: 71.2 ÷ 0.25 = 284.8 liter
Vn : 300 liter ==> STANDARD: LR 300/6 IS CHOSEN.
SAMPLE ACCOUNT II
Calculation of the expansion tank to be selected for a boiler with a heating power of 180,000 kCal/h operating at 70/50 °C in the steel panel radiator system of a 4-story and 16-flat apartment; boiler operating pressure is 5 bar. According to this;
Static Pressure: 4 x 2.8 + 3 ==> 14.2 ÷ 10 = 1.42 bar.
Front Gas Pressure: 1.42 + 0.1 = 1.52 ==> 1.5 bar. (22 lbs)
Normal Volume;
Total water volume in the system
Vs= Q x f = 180.000 x 12 ÷ 1000 = 2160 Liter
Expanded water volume in the system:
Vg= Vs x n = 2160 x 0.0356 = 76.89 Liter
Genleşme Deposunun Normal Hacmi;
Vn = Vg ÷ K (Front Gas Pressure: 1.5 bar Safety valve (3-0.5)= 2.5 bar)
K: to Table 3 K = 0.28
Vn= 76.89 ÷ 0.28 = 274.6 Liter
Vn= 300 lt STANDARD : LR 300/6 is chosen.