Dimplex LA 12 MI, Installation & Technical Manual

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Page 23
Filter
It is essential to install a filter immediately before the
water inlet to the heat pump. Not installing this filter
would invalidate the warranty of the heat pump as
debris can easily block the condenser channels.
The MFK114 isolation valve as shown in Figure 14 is
included in the heat pump packages. The valve can be
closed and the filter removed and checked without
having to drain the system.
Figure 14: Isolation valve and filter supplied in LA MI
packages to be fitted to the heat pump return.
Figure 15: Isolation valve supplied in package to be fitted
to the heat pump flow.
Filling the system
The system should be filled with potable water. The
system water should be treated with standard central
heating inhibitors.
The cold fill gauge pressure on the heat pump should
be between 0.8 and 1.5 bar (0.08-0.15MPa). This will
rise during normal operation.
De-aeration
Air trapped in the system causes air locks which in turn
cause poor water flow around the system. Every high
point in the system should have a means of bleeding
out air which is supplied by the installer.
The pressure relief valve shown in Figure 17 can be
used to purge the air from the heat pump during filling.
Figure 16: Location of pressure relief valve
Figure 17: Pressure relief valve
Adjusting the water flow rate
The default setting is moderate speed (III). The
circulation pump must be adjusted to give a suitable
flow rate to maximise system operation. The heat
pump should be turned on and the compressor
allowed to reach maximum frequency. Once this
frequency is reached the pump speed should be
adjusted so the difference between the flow and return
is as close to 5

C as possible. If the difference is
greater than 7

C this would potentially cause nuisance
tripping of the flow alarm.
Expansion vessel sizing
The heat pump comes with an expansion vessel
installed as shown in Table 13. Dependant on the
static height of the system and the volume it may be
necessary to install a second expansion vessel.
Depending upon the specific system the
installer must determine if a second
expansion vessel is required.