A filter is located upstream of the solenoid. This has a removable element to
simplify cleaning. The filter connections suit a 12.5mm (½”) hose from the
supply tank. A small pump may be operated if an underground water supply
is used.
5.4.4
Drain System
A small pump is used to remove surplus water (rainfall) from the pan. If the
data logger detects the water level is higher than the reference at the reset
time (0900hrs), the pump is turned on until the level is correct. The pump is
also switched on to reset the pan level if rainfall increases the tank level to
240mm. The pump has the advantage of moving the water quickly and being
able to recycle it to a tank.
The pump mounts in a housing designed to stand within the evaporation pan,
and discharge water over the side through a 12.5mm (½”) hose fitting. A hose
can be connected to this fitting to direct the pumped water to storage or away
from the site.
The end of any drain hose should discharge into air at a higher level than the
pan top to prevent water siphoning in or out of the tank.
The submersible bilge pump is installed inside a small housing made from
PVC. Terminals beneath the lid connect the pump with the cable to the
control system. The pump housing can be lifted from the well, separated in
the middle and the pump lifted out for cleaning. The bottom of the pump can
be removed to clean and service the impeller.
The pump must be inverted when installed for reliable self-priming; the inlet
must be at about 190mm above the pan bottom. This prevents a
malfunctioning pump from draining the evaporation pan.
5.4.5
Power Supply
The system is powered by a 12-Volt, 7 Ampere-Hour sealed lead acid battery.
This is recharged by a 12-Volt 2-Watt solar panel located on the top of the
enclosure. A regulator on the relay card maintains the battery in a fully
charged condition. This will power the level control system for an expected
service life of at least three years.
The battery capacity is sufficient for up to two months of operation, without
recharging. When the sun shines the solar charger can replace the typical
daily power consumption within one hour.
Automatic Evaporation System
INSTALLING THE EQUIPMENT 27
5.4.6
Installing The Level Control System
There is a row of 16 pluggable terminals on the level control module. A strip
of 8 terminals permanently connects the data logger, GSM modem and solar
panel. Strips of two terminals are used to connect the battery and the drain
and fill devices. The Test socket is normally empty. You can plug in the
Drain or Fill device at any time to test it or to manually adjust the pan water
level.
UNIDATA
28 INSTALLING THE EQUIPMENT
