The efficient storage of the solar energy gained from the collectors is crucial
to the successful operation of the whole system. The storage volume must at a minimum provide for
the normal daily consumption of the household, but ideally, given the variability of our weather
should also provide for the next day as well. This raises issues with the level of heat loss from
the cylinder, the integration of the auxiliary heating system, the size of the area available for
the hot water cylinder (the strength of the supporting floor and the size of doorways for
installation access) and the prevention of overheating of the solar collectors in spells
of prolonged hot weather. The type of hot water cylinder chose will depend on the type
of system design that has been adopted. The range of cylinders employed varies from the
modified use of the existing cylinder if it is still compliant with insulation
regulations (BS ***) to the use of system specific polymer stores.
While much attention is provided to the main cylinder insulation,
the heat loss through the connections is often neglected. These can be
substantial particularly for connection near the top of the cylinder, where it is
warmer. Check valves, s-bending (180 o loops) or specilaist connections such as
Convectrol can be used to minimise these losses.
Desirable Solar Cylinder Properties
- High level of insulation of the cylinder.
- Good stratification of heated water in the cylinder.
- Prevention of heatlosses from cylinder connections.
- Sufficient storage volume for the daily demands of the household.
- Ability to control the auxiliary heating system.
- Provision of a reserved solar space that may be defined as a permanent
physical volume or a volume reserved in time by interlock of the auxiliary heating
- Means of minimising legionella risk
The immersion heater is normally pre-fitted to the cylinder. All heaters are factory pre-wired
with a 1 meter long heat resistant 4 core cable, ensure that all connections are tight
before switching on.
The thermostat is wired through the neutral, the brown wire goes to the bath element,
and the black wire goes to the sink element. It is very important to ensure that the
heater is earthed correctly.
With the cylinder full of water, heat the cylinder to 60C via the immersion heater or
central heating system. Adjust the thermostat so that it just turns off at 60C.
Anti-Legionella. Normally an immersion heater timer is wired in front of the Sink/Bath Switch,
so that this can be used to provided a timed source of heat. This is a SEI requirement.
It is common necessary to replace the cylinder when installing a solar system.