E93.1001EN.C Manual CD
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9.6
Equivalent lengths – table
When the water heaters and tanks are separated over some distance, the interconnecting pipes may only have a
certain maximum length, dependent of the number of bends and the like components. For every applied compo-
nent a so-called ‘equivalent length’ is deducted from the total allowed.
The meaning of the connection ‘VL’ can be seen in the drawing below.
The diameter of this connection VL should meet at least the specified pipe diameter D. For this pipe connection
the maximum straight length
of flow and return part added *
has been specified in the table below.
*
The real available maximum distance VL between water heaters and tanks is therefore half of the
length specified in the table!
Figure 9.3 Drawing in which pipe connection ‘VL’ is displayed
Each component that’s added to the straight pipes is contributing to the total resistance, and will therefore cause
a necessary reduction of straight length. The table contains a number of commonly used components and their
equivalent length:
Copper
pipe
diameter D
Maximum
straight length
flow + return
equiv. length
90° elbow
R=0.5
D
equiv. length
90° elbow
R=1.0
D
equiv. length
45° bend
R=1.0
D
e.l. of fully
ported
ball valve
mm
mm
m
m
m
m
m
42
1,4
22,7
2,5
0,9
0,5
0,4
54
1,5
24,2
2,8
1,0
0,6
0,4
67
1,9
26,1
3,3
1,1
0,7
0,5
80
2,1
28,5
3,8
1,3
0,8
0,6
93
2,3
31,9
4,6
1,6
0,9
0,7
106
2,5
36,7
5,7
2,0
1,1
0,9
133
2,8
44,3
7,5
2,6
1,5
1,1
159
3,0
58,2
10,8
3,8
2,2
1,6
Table
E: Equivalent lengths
Example:
Suppose, for a project the diameter D has been specified the value 106
2,5, so the maximum allowed straight
length is 36,7 m (see table).
In the connection is added
•
4
bend 90°, R=0,5
D
•
2
fully ported ball valve
This gives a reduced allowed straight length of:
36,7
−
(4
5,7)
−
(2
0,9) = 12,1 m
With this component configuration one may only use
12,1 m straight length
.
→
The distance between water heater main connections and tank main connections in this example is therefore
~6 m at max.
VL
