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will significantly reduce short cycling and nuisance alarms such as low flow rate. It is also
essential to provide freeze protection as detailed in section 3.4.5.
3.4.5 Freeze Protection
Freeze protection works in a number of ways depending on the current operation and conditions
at the unit. When the unit is running, freeze protection is enabled if the outlet water temperature
is more than 2°C below the inlet water temperature and is also less than 5°C. This may be the
case if the unit is trying to defrost but there is not enough energy in the heating system to utilise.
When these conditions are met, the unit will stop the compressor but continue to run the
circulating pump. The unit will exit this freeze protection mode when the outlet water
temperature rises above 7°C and the suction pressure in the refrigeration circuit is above 0bar.
NOTE: If this type of Freeze Protection is triggered 3 times within 30 minutes, the unit will
not start up. Power to the unit needs to be turned OFF and then back ON in order to
perform a reset and confirm that everything is OK with the system. The unit will start up
and operate as normal after this reset.
When the unit is not running or in standby mode, there are two stages of freeze protection built
into the unit. In the first stage, if the temperature of the heating medium falls below 4°C within
the unit and the ambient temperature is less than 0°C, the unit will automatically start up the
circulating pump to increase the medium temperature and prevent it from freezing. Therefore
the unit needs to have a permanent electricity supply and be connected to a heating system
which can always provide a complete circuit in order to achieve the minimum heating flow rate.
The unit will exit freeze protection mode when the heating medium temperature rises above 8°C
or the ambient temperature rises above 1°C.
In the second stage, if the temperature of the heating medium falls below 2°C within the unit
and the ambient temperature is less than 0°C, the unit will automatically start up the compressor
and run in heating mode to increase the medium temperature and prevent it from freezing.
Again, the unit needs to have a permanent electricity supply and be connected to a heating
system which can always provide a complete circuit in order to achieve the minimum heating
flow rate. The unit will exit freeze protection mode when the heating medium temperature rises
above 15°C or the ambient temperature rises above 1°C.
3.4.6 Heating Circuit Line Components
Together with the heating system, associated pipework and manifolds, the heating circuit will
also require the following items, expansion vessel, strainer/filter, filling loop, drain valve,
pressure gauge, pressure relief valve and isolation valves. A full flow 3-port motorised valve
may also be required for some systems; this can be ordered separately, please contact
Warmflow for details. Please see section 3.9 for more details of installing and wiring the 3-port
motorised valve. These air source heat pump units come with the following items included
integrally, a high flow circulating pump, a manual air vent, flow switch and temperature sensors.
A strainer/filter, isolating valves, elbows and a set of flexible hoses are also supplied with the
units as standard.
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