17
10.1.6
EXPANSION VESSEL SIZING
The following information is based on an inlet pressure of 3.5 bar. If a different inlet pressure is to be used, please
consult BS6700.
V V =
0.45
S V * e
Where:
V V
=
Vessel Volume
S V
=
System Volume
e
=
Coefficient of Expansion
(See Table 10.1)
Stored
Temp.
°
C
30
35
40
45
50
55
60
e
0.005
0.006
0.008
0.010
0.012
0.015
0.017
Stored
Temp.
°
C
65
70
75
80
82
85
90
e
0.020
0.023
0.026
0.030
0.031
0.033
0.037
TABLE 10.1
COEFFICIENT OF EXPANSION OF WATER AT 3.5 BAR INLET PRESSURE
10.1.7
DE-STRATIFICATION
If the hot water system does not include a constantly circulated building return, it is recommended that a de-
stratification pump be fitted, between the flow connection and the circulation connection on the right hand side of
the storage vessel, to ensure an even temperature distribution throughout the stored water. De-stratification pump
kits are available as ancillary items; please contact Lochinvar Limited for details.
10.1.8
CIRCULATING PUMPS
In order to ensure the correct flow rates through the water heater, the unit requires a bronze glanded pump sized
to overcome the resistance of the heat exchanger and a primary pipework loop. The primary loop should be no
longer than 14 metres plus the following fittings:
6 x 90
°
Elbows
2 x Unions
2 x Full bore lever ball valves
2 x Tee fittings (cold feed & HWS return)
For longer distances or a greater number of fittings, the pump may have to be resized.
The specification of this type of pump ensures that the bronze body and associated parts in contact with water are
suitable for potable use. A "glanded" construction is required to ensure that any scale in the system does not build
up within the pump and cause a resistance that can lead to a loss of water flow. Glandless (canned rotor) pumps
are not recommended by Lochinvar Limited due to the fact that in hard water areas, scale can build up within the
rotor and failure can occur, not only of the pump but also the heater itself. The warranty will be void if a failure of
the heat exchanger occurs due to a "glandless" pump.
