Expansion vessels for heating systems, domestic hot water and Pressure tanks
Expansion vessels, Pressure tanks, Heat exchangers, Solar Boilers
Quality solutions for all volumes
Italian Quality
Technical Support | Sizing Expansion vessels Multifunction |

Dimensioning of an Expansion vessels Multifunction for domestic hot water use

The dimensioning of the expansion vessels for domestic water systems requires the same formula of the heating systems.

Dimensioning of an expansion vessel as water hammer arrester

The calculation of the storage volume against water hammer is essential to protect the system. Two formulas are provided for two different cases: first, in which the system pressure (P) is known; second, in which the flow (Q) of the system is known.
Knowing the pipe diameter, (D) crossing flow and pressure values as in the table below then could be obtained the linear capacity value (C).
In the case in which the flow is known/round up, if the value given is not equal to the one given by the table, then make a rounding up to obtain the value:
Qa Approximate flow (m3/h), the approximate value in the table immediatly above the..

Table of calculation of the linear capacity C

D (“) 1/2” 3/4” 1” 1,5“ 2” 2,5“ 3” 3,5” 4”
Velocità - Speed (m/s) 1.12 1.19 1.38 1.48 1.47 1.5 1.58 1.62
Q (m3/h) 0.9 1.5 3.0 7.0 12.0 19.0 27.0 37.0 48.0
P (bar) Minimum linear capacity of the vessel (lt./m)
5 0.0457 0.0568 0.1271 0.3077 0.5087 0.8162 1.1447 1.5793 2.0191
6 0.0200 0.0248 0.0557 0.1348 0.2229 0.3576 0.5015 0.6920 0.8847
7 0.0120 0.0149 0.0335 0.0811 0.1342 0.2153 0.3019 0.4166 0.5326
8 0.0084 0.0104 0.0234 0.0568 0.0939 0.1507 0.2113 0.2916 0.3728
9 0.0064 0.0080 0.0179 0.0433 0.0717 0.1150 0.1613 0.2226 0.2846
10 0.0054 0.0064 0.0144 0.0350 0.0578 0.0928 0.1302 0.1796 0.2296
11 0.0043 0.0054 0.0121 0.0293 0.0485 0.0778 0.1091 0.1506 0.1925
12 0.0037 0.0046 0.0104 0.0253 0.0418 0.0671 0.0941 0.1298 0.1660
13 0.0033 0.0041 0.0092 0.0222 0.0368 0.0590 0.0828 0.1141 0.1461
14 0.0029 0.0036 0.0082 0.0199 0.0329 0.0528 0.0710 0.1022 0.1307
15 0.0026 0.0033 0.0074 0.0180 0.0298 0.0479 0.0671 0.0926 0.1184

Given l = pipe length (m), the formula to calculate the adequate storage volume (V) is as follows:

1) Pressure known:  V=C·l
2) Flow known: V=C·l ·(Q/Qa) 2

The adequate expansion vessel will be the one with capacity immediately above V.
CD-ROM ‘Varem strong points’, available on demand, contains a calculation application

Example of calculation with flow known

l = 180 m pipe length
D= 1” pipe diameter
Q = 2,5 m3/h --> Qa = 3 m3/h flow known (Q); approximated flow (Qa)
C = 0.1271 linear capacity (see table)

V = 0.1271 l/m · 180 m · (2.5 m3/h / 3 m3/h)2 = 15.89 l ------------> Extravarem LC R1 18 lt.



Limena
Via del Santo, 207 - 35010
Limena Padova Italy
Tel.+39 049 8840322
Fax +39 049 8841399

Via Sabbioni, 2 - 35024
Bovolenta Padova Italy
45° 16’ 02.49” N, 11° 55’ 51.49” E

Name: *
Company: 
E-mail: *
Privacy: Consent to the data treatment according Disclosure GDPR art.13 EU 2016/679
Varem S.p.a. © Copyright 2013 - P.IVA 01010270286 - All rights reserved