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Solahart Owner’s Manual – Thermosiphon Systems - Revision 3
5
Backup Electrical Heating
Primary heating of your hot water system will be from solar energy. The solar heating requires no operation by the user.
Systems fitted with a backup electrical heating unit can heat the water at times of low solar energy gain, such as during very
cloudy or rainy weather, or during the colder months. The electrical heating unit also provides the means to inhibit the growth
of bacteria in the water tank.
The backup electrical heating unit includes an immersion element, a thermostat that controls heating operation and an energy
cut-out (ECO) for electrical safety. The element is positioned approximately at the middle position of the tank water volume.
Electricity to the heating unit MUST be supplied via an Isolating Switch installed in the electrical switchboard.
The thermostat is factory preset to 60°C and has a maximum temperature setting of 70°C. When the water is below the
thermostat setting, the heating element will turn on and heat the water volume above it. The heating element will turn off
when the temperature of the water reaches the thermostat setting. If the water temperature drops below the setting again the
heating element will re-activate.
Individual situations may require this setting to be altered. Only a suitably qualified person is permitted to adjust the
thermostat temperature setting.
The overall performance and energy savings that you will obtain from your Solahart water heater will depend on your hot
water usage pattern and the operation of the backup heating unit. A suitably rated timer control switch connected to the
power supply can help maximize energy savings with a solar water heater fitted with a backup heating unit.
ENERGY CUT-OUT OPERATION
The ECO of the backup heating unit will de-energize the element should the temperature within the tank reach 83
°
C when the
element is activated.
Should a fault occur with the Thermostat unit, the ECO will terminate electricity draw to the backup heating unit. If this occurs
backup heating will not operate until the Thermostat/ECO assembly is replaced. The Thermostat/ECO assembly must be
replaced by a suitably qualified person.
Temperture Stratification and Stabilization
During day time with normal solar gain a natural temperature gradient known as stratification occurs inside the tank, where
the hotter water layers shift to the top and the colder layers settle at the bottom. This hot to cold variation inside the tank is
highly desirable as the water delivered from the heater will come from the hottest part of the tank. The utilization of the hot
water in this manner through the night and the following morning maximizes the opportunity of heat gain during daytime.
When there is no solar gain, the stratification described above gradually reduces as the hot water at the top of the storage
cylinder transfers some of its heat to the cooler water in the lower section of the cylinder. Known as stabilization, this effect
is often perceived as heat loss, but is actually the redistribution of stored heat more evenly over the entire contents of the
storage tank. This heat is not lost to the system and is more prevalent when more hot water is used the night before and also
in periods of lesser solar gain.
Water Supplies
This water heater must be installed in accordance with this advice to be covered by the Solahart warranty.
This water heater is manufactured to suit the water conditions of most public water supplies. Water supplies where the
saturation index ranges between -1.0 and +0.4, and the level of total dissolved solids in the range of 40mg/L to 600 mg/L are
considered suitable for this water heater.
However, there are some known water chemistries which can have detrimental effects on the water heater and its operation
and / or life expectancy. If you are unsure of your water chemistry, you may be able to obtain information from your local
water supply authority. This water heater should only be connected to a water supply which complies with these guidelines
for the Solahart warranty to apply.
The vitreous enamel lined cylinder of the water heater is only covered by the Solahart warranty when the total dissolved
solids (TDS) content in the water is from 40mg/L to 600 mg/L.
Anode Inspection and Replacement
The anode installed in this water heater will slowly dissipate whilst protecting the cylinder. The life of the cylinder may be
extended by replacing the anode. The changing of an anode must be carried out by a qualified person.
For water supplies which are either softened or desalinated, or where the water supply may alternate between a water tank
and a reticulated public supply or another supply, or where there is a variable supply (e.g. from a bore or public reticulated