Solex Roofing Installation Manual 31
Solex Energy Ltd +44(0)1305 837223 www.solexenergy.co.uk
Plumbing Installation – solar hot water systems
Hot water systems store solar heated water in a hot water cylinder. The cylinder itself may
be either the
pressurised/unvented/mains pressure
type, or it may be the less
expensive
vented
type fed from a cold water tank in the loft. This choice does not affect
the operation of the solar heating.
Whatever arrangement is used, provision must be made to kill off legionella bacteria
(which can grow in temperatures between 20
o
C and 45
o
C) for example by heating the
water up to 60
o
C at least once a week. One method to achieve this is by means of an
immersion heater with a suitable controller unit – e.g. a simple timer and cylinder stat.
Systems using a new solar cylinder:
System boiler –
a new twin coil cylinder is fitted
to replace the existing single coil one, with the
solar collector heating the whole cylinder from
the bottom, and the boiler topping up the
temperature in the upper section when required.
1) Twin coil cylinder, 200 - 300 litres capacity
2) Solar pump circulates water from tank
3) Solar roof, heats water
4) Cylinder coil heats cylinder from bottom
5) Boiler coil tops up if necessary
6) Hot water out
Combination boiler –
a single coil cylinder is
installed with the solar connected to its coil. If
the boiler is ‘solar compatible’ and thus accepts
pre-heated hot water, then the output from the
cylinder may be fed through the boiler to the
taps. A cylinder of 120 - 150 litres is usually
used for this purpose. [2x combi diagrams]
Where a combination boiler is not ‘solar
compatible’, then a three port valve is used to
select water from either the boiler or from the
cylinder. The three port valve is controlled by a
tank thermostat at the top of the cylinder, which
is set to the minimum acceptable temperature
for hot water use.
