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12.3
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 TTW water heater and any primary pipework loop. Lochinvar will supply a
suitable bronze glanded shunt pump with every TTW water heater sized to overcome the resistance of the TTW
water heater plus the following primary pipework loop:
14 metres of pipe sized according to table 12.4.2
4 x 90 elbows
2 x Unions
2 x Full bore lever ball valves
2 x T fittings (cold feed and building return)
For installations with Longer Primary, pipework loops or a greater number of fittings please
contact Lochinvar Technical support before proceeding with any installation.
The specification of this type of pump ensures that the bronze body and associated parts in contact with water
are suitable for use with potable water. A glanded construction is required to ensure that any scale or deposits
within 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) must not be used with TTW water heaters due to the fact scale can quickly build
up on the rotor in hard water areas causing early and sudden failure not only of the pump but of the TTW water
heater as well.
The use of glandless (canned rotor pumps) will invalidate the warranty of the TTW water
heater
MATCHED PRIMARY CIRCULATION PUMP
Pump for models TTW410 & TTW580
12.4
PRIMARY PIPEWORK LOOP SIZING
The pipework header between the TTW water heater(s) and LST(s) buffer vessels must be
sized as per the guidance given in this section. Failure to use the correct pipework header size
will cause operational problems and potential early failure of the water heater: this will not
be covered under the water heater warranty.
If the installation is outside the scope of this guidance, please contact Lochinvar Technical
support before proceeding with the installation.
Minimum Water Flow
Pressure Loss – Heat Exchanger
Pressure Loss – Internal Piping
Pressure Loss – Water Flow Switch
Pressure Loss – Total (Appliance)
Differential Temperature – High Fire – nom.
Differential Temperature – High Fire – min.
Differential Temperature – High Fire – max.
12.4.1
CIRCULATION REQUIREMENTS
Using the example schematics shown in section 12.4.2 and assuming the TTW water heaters are TTW410 in both
cases the primary pipework header would be sized as:
Single unit = as there is only one TTW water heater there is no common header so all pipework should be sized as
per A blue at 76mm
Two units = the common header shown in red should be sized according to the table B-red at 108mm with the
pipework between each water heater and the header sized as per A-blue at 76mm.
PART NUMBER
LM900149A
TTW410
3
m
/hr
20.22
m H
O
5.4
2
m H
O
0.08
2
m H
O
1.0
2
m H
O
6.48
2
K
17.7
K
15.6
K
19.8
TTW580
26.94
5.4
0.08
1.0
6.48
18.3
16.2
20.4
35
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