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13
Commissioning
6.6 Connection of Secondary Return
For cylinders that do not have a dedicated
secondary return connection, it is possible to
install a secondary return by connecting a swept -
T to the cold water inlet of the cylinder (see Figure
10).
The secondary return pipe should incorporate
a check valve and a WRAS approved circula-
tion pump; timer and thermostat to be provided
separately. Where secondary return circuits are
used, then an additional expansion vessel may be
required.
The secondary return loop must avoid:
- stagnant water in long pipe runs
- long waiting times at draw off point for hot water
- undue water wastage
To minimise the energy consumption of the sec-
ondary return circuit and to ensure reliable opera-
tion it is important to consider:
- the control of the circulation pump to be time
and temperature controlled
- the secondary return circuit pipe work to be
insulated
- the secondary return pump to be of suitable
materialandspecication
HW Outlet
To Taps
From Taps
Swept-T
Figure 10: Secondary Return Loop
7 Commissioning
At the time of commissioning, complete all
relevant sections of the Benchmark Checklist
located on the inside back pages of this
document.
The following commissioning procedures only
detail the required steps to be taken for the
potable water loop:
1) Before making any mains connections to
theinletcontrolgroup,ushthemains
pipework out
to ensure all debris has been removed so
as not to damage the strainer within the
combination valve.
2) Makenalmainsconnectionon
combination valve and check all
connections and joints to ensure they have
been tightened and secured correctly.
3) Before turning on the mains supply to the
cylinder a hot water tap should be opened,
preferablyonthesameoorortheoor
below where the cylinder is located.
4) Check the pre-charge in the expansion
vessel and ensure it is at least 3 bar. Note
actual pressure on label on expansion
vessel.
5) Turnonthesupplytothecylinderandll
until water runs from the open hot water
tap.Continuetoushthesystemuntilall
debris has been removed.
6) Close the hot water tap.
7) Check all joints for leaks, even those not
having been altered especially when
replacing a vented cylinder.
8) Open temperature and pressure relief valve
to ensure proper discharge and check after
closing that valve is not dripping.
9) Open expansion relief valve to ensure
proper discharge and check after closing
that valve is not dripping.
10) Check all shower outlets, toilet cisterns and
other draw off points for leaks or dripping
(especially when replacing a vented unit).
Open all water outlets to purge air from
pipe work and ensure proper operation.
11) Instruct user in the operation of the unit
and hand over this manual advising the
owner of annual service requirements.
12) Complete the technical data label on the
cylinder with legible and permanent
writing.
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