Table 13: Size of expansion vessel in the LA MI range
For most installations the 10L expansion vessel should
be able suitable with a volume up to 200L and a static
height of 7m. The 5L expansion vessel should be
suitable for a system volume up to 100L and a static
height of 7m.
2 port valves
The heat pump packages include 2 x F228 Horstmann
two port valves as shown in Figure 18 to switch
between space heating and domestic hot water mode.
Fit the valves ensuring that the actuator head is not
below the horizontal level of the pipe work and that the
flow is in the direction of the arrow. Remember to
make allowances for maintenance and replacement.
Figure 18: Dimensions of F228 valve
Controlling DHW temperature
The cylinder temperature is controlled via an NTC2
sensor.
For safety reasons the heat pump controller also
checks for continuity from the DHW thermostat. The
temperature regulation thermostat and high limit stat
are wired in series. To keep the contacts closed on the
regulation stat the dial must be set to maximum. The
contacts on the high limit stat will remain closed during
normal operation. If the heat pump does not detect
continuity across both the regulation stat and high limit
stat an H91 error will occur.
A label similar to that shown in Figure 6 should be
supplied by the installer and fixed on the cylinder to let
the user know.
Figure 19: Notice to be supplied by the installer and fixed
next to cylinder thermostat
TEMPERTURE ADJUSTMENT
The temperature of the hot water in this
cylinder is set using the wall mounted heat
pump controller. The setting shown on this
thermostat does not affect the hot water
temperature.
For normal operation the dial should be
set to the maximum position.
The F228 valves have been specifically
selected for their fast operating times. When
switching from heating to DHW the heat
pump flow must not be restricted. If a
different valve is used, the valve must be
fully open within 6 seconds of being
switched.
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