Bosch BSS250E-2 Installation And User Manual page 41

SolaStat-Eco Plumbing Issues, Cont.
5. Cavitation.
A pump is used to circulate the water between the tank and the collector.
If the pressure at the inlet or impellor of the pump falls below the vapour pressure of the liquid
being pumped, cavitation will occur. Cavitation in a pump is more likely to occur as the
temperature of the water rises and/or the pressure of the water decreases.
Bubbles form when the water is sucked into the pumps impellor and collapse again as small
implosions when the water is ejected out of the impellor which can be so rapid that a
rumbling/cracking noise is produced (it sounds like stones passing through the pump) and
there can be damage to the impellor and other sensitive components as well as a drop in
water volume moved.
Mains pressure solar hot water systems are less susceptible to cavitation than low pressure
systems as the extra pressure will make it less likely that vapour bubbles will form.
The SolaStat-Eco controllers have an optional factory setting called „Pump Timer‟ to assist in
pump cavitation recovery. After the pump has run continuously for approximately ten minutes,
it will turn off for one minute. This cycle is repeated as long as the pump is required to run and
will not affect normal operation in a standard hot water collector and cylinder installation.
The one minute turn off period helps any accumulated air to escape from the pump and has
been effective as a backup in exceptional conditions. This should not be considered a
substitute for the afore mentioned best plumbing practices. This feature can help prevent the
pump running for hours in a „locked up‟ state, increasing the installation reliability.
GRUNFOS PUMP
The pump supplied is a Grunfos UP 15-14 and suitable for most domestic single and double
storey applications. The pump is mounted in a waterproof mounting box with the solar
controller fixed to the front of the box. Typically the „Solar pump Station‟ is mounted on a wall
adjacent to the tank.
The water-conduction part of the pump is hermetically separated from the stator with a
stainless steel spherical separator. The motor can be separated from the pump housing,
enabling easy maintenance and replacement.
MOTOR
240v/50Hz, enclosure class IP42, Insulation class F.
AMBIENT AND LIQUID TEMPERATURES
+2°c to +95°c
It is recommend to keep the operating temperature as low as possible (e.g 65°c) to avoid lime
precipitation.
MAXIMUM SYSTEM PRESSURE
1.0Mpa (1000 kPa)
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