H E A T I N T E R F A C E U N I T
I N S T A L L A T I O N
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H E A T I N T E R F A C E U N I T
C O M M I S S I O N I N G
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7.5.2 Wiring Diagram (Underfloor Heating)
8. COMMISSIONING
Open the kitchen sink DHW tap to allow the
water to flush through the system
Open the DHW isolation valve at the top of the
HIU
Open the MCW isolation valve at the top of the
HIU
8.1 Before Filling the HIU
CAUTION
Flushing and back flushing through the HIU is
strictly prohibited, performing this action will
damage the HIU / Components. Failure to follow
this instruction will invalidate the HIU warranty.
Fig. 14
Refer to Section 3 with regards to tightening of
connections
Obtain pressure test certificates for the MCW,
DHW and HTG systems
Confirm that the Primary side connections
have been completed and are live
Obtain test certificates to show that all
pipework has been flushed / cleaned prior to
connecting the HIU
WARNING
Chemical inhibitors can cause serious injuries.
Always consult manufacturer’s instructions.
Run the water through the kitchen sink tap until
a cold, clean, steady flow of water is achieved
Open each DHW outlet within the property until
all air and any remaining debris has been flushed
through
Check HIU for leaking joints on the secondary
MCW and DHW connections, tighten connections
as required. Do not overtighten the fibre washers
as this will result in damage. Should a fibre
washer become damaged, replace the washer
immediately ensuring to isolate the HIU
mechanically and electrically first
Once all taps have had water drawn off and no
leaks are evident, move to the next step identified
in 8.2.2
Ensure that both drain valves identified in Fig.
14 are closed and end caps are fitted and tight
Confirm that there is an electrical supply to the
HIU which has been isolated
8.2 Filling the HIU
with Water
8.2.1 Filling the Secondary MCW and DHW
System
8.2.2 Filling the Secondary Heating System
Open the secondary HTG isolation valves at the
top of the HIU (always open the return valve first
to prevent debris entering the HIU)
Before filling the secondary HTG system introduce
a suitable inhibitor for the type of system
installed, in accordance with the manufacturer’s
instruction and BS 7593
Ensure that both valves identified in Fig 15 are
fully closed
Fig. 15
