10 filling the system, Filling the system – Grant Products HPAW155 User Manual
Filling the System
10 Filling the System
10.1 Filling and Venting -
1. To vent the heat pump – All Grant
Aerona heat pumps are fitted with a
single automatic air vent on the top
of the electric immersion element
Check that the small cap on the
automatic air vent is screwed on
fully, then unscrew it one complete
turn - leave the cap in this position.
Note. Cap is supplied loose in bag
attached to air vent.
2. Before filling the system check
charge pressure in the expansion
vessel (as supplied in the Sealed
This should be 0.2 – 0.3 bar higher
than the cold fill pressure for the
The nominal filling pressure for the
system when cold is 0.5 -1 bar.
3. If a flexible filling loop is to be used
to fill the system (as supplied in the
Sealed System kit), ensure it is
connected between the two filling
valves and that both valves are
A valve is open when the operating
lever is in line with the valve and
closed when at right angles to it.
4. To fill the system, ensure that the
mains cold water supply valve (stop
cock) is open, then open the filling
valve on the cold water supply.
Gradually open the filling valve on
the heating circuit (at the other end
of the filling loop) until water is
heard to flow into the system.
Fill the system until the required
system pressure is indicated on the
sealed system pressure gauge (as
supplied in the Sealed System kit).
Then close both filling valves.
5. Vent each UFH circuit and then
each radiator in turn, starting with
the lowest one in the system, to
6. It is important the circulating
pump(s) are properly vented to
avoid them running dry and the
bearings being damaged.
7. Check the operation of the safety
valve (as supplied in the Sealed
System kit) by turning the head
anticlockwise until it clicks. The click
is the safety valve head lifting off its
seat allowing water to escape from
the system. Check that this is
8. After venting, check system
pressure and top-up using the filling
loop, as required.
10.2 Flushing and Corrosion
To avoid the danger of dirt and foreign
matter entering the Heat pump the
complete heating system should be
thoroughly flushed out – both before
the heat pump is operated and then
again after the system has been heated
and is still hot.
This is especially important where the
heat pump is installed as a replacement
for a boiler on an old system.
In this case the system should be first
flushed hot, before the old boiler is
removed and replaced by the heat
For optimum performance after
installation, this heat pump and the
central heating system must
be flushed in accordance with the
guidelines given in BS 7593:1992
'Treatment of water in domestic hot
water central heating systems'.
This must involve the use of a
proprietary cleaner, such as Betz
Dearborn Sentinel X300 or X400, or
For long term protection against
corrosion and scale, after flushing, it is
recommended that an inhibitor such as
Betz Dearborn Sentinel X100 or Fernox
MB-1 is used in accordance with the
guidelines given in BS 7593:1992.
Full instructions on the correct use of
system cleaners and corrosion
inhibitors are supplied with the
products, but further information can be
obtained from www.betzdearborn.com
Failure to implement the above
guidelines by fully flushing the system
and using a suitable corrosion Inhibitor
will invalidate the Heat Pump product
To avoid the risk of the freezing in the
external section of the heating system
(i.e. the flexible hoses, condenser and
circulating pump within the heat pump
casing) in the event of power failure
during winter months, a suitable
domestic heating system antifreeze
should be used. This is added to the
system water when finally filling the
Full instructions are supplied with the
system antifreeze, but immediate
information can be obtained from
As with all wet
heating systems, it is
the responsibility of
the installer to
remove all the air
from the heating
system after filling.
For technical details and requirements
for Sealed Systems, refer to Section 7
of these instructions.
For details of the Grant Sealed
System kits for use with the Grant
Aerona heat pump range refer to