61
13.5 Monitoring a Solar Pump System
Monitoring the pump Will you be able to
observe the output of your pump at the point
of discharge? If not, you may not know if it
malfunctions. Consider installing a water
meter, or additional valves so that the flow can
be directly observed. (See illustration in
Section 13.4)
13.6 Freeze Protection for Solar Water Pumps
In a cold climate, water can freeze in a pipe
and block the water flow. This will cause an
electrical overload that will cause the pump to
stop.
Pressure relief If there is any possibility of a
pipe freezing, install a pressure relief valve to
prevent excess pressure in the pump line.
Install it below frost line. Adjust the valve to
open if the pressure exceeds normal. This is
especially important for helical rotor pumps
(model number not containing “C”) which can
develop very high pressure.
Burial of pipe The best way to prevent
freezing is to bury all piping below frost line.
The modern method of burial at the wellhead
is to install a pitless adapter (see section 13.3,
Wellhead Assemblies for Drilled Wells).
Weep hole If you have above-ground piping
that must be drained for freeze protection,
make a tiny “weep hole” in the drop pipe,
below frost line. This will cause a constant
(but very small) leakage of water back into the
well. When the pump stops, the pipe will drain
back slowly. The pipe must be sloped without
low spots, so it drains completely. In plastic
pipe, a weep hole can be made with a hot
needle or an extremely small drill bit, or a
needle valve can be installed and adjusted.
Weep hole – “high tech” version The most
reliable way to control dripping is to use a
“drip emitter” made for drip irrigation systems.
It will resist accumulation of debris and
WARNING Do
not install the
pump with its
check valve
removed.
Question: Will
the pump drain
back when it
stops?
Answer: NO! The
pump has a check
valve that stops
water from
draining back
down when it
stops. A helical
rotor pump will
not drain back
even if the check
valve is removed.
mineral deposits far better than a simple hole
or a needle valve. Emitters are available from
irrigation suppliers, nurseries, and many
hardware stores. They are rated in gallons
(liters) per hour. The most common ones are
in the range of 1-2 gallons (4-8 liters) per
hour. Use a relatively fast one for best
reliability, especially if you get mineral depos-
its. Drill a hole in the pipe to fit the emitter,
and push the emitter into the hole.
Drip emitters are made for a pressure limit of
about 40 PSI (2.8 bar). This limits the vertical
lift above the emitter to about 90 feet (28 m).
In cases of relatively high lift, use a “pressure
compensated” emitter. It will maintain a
relatively constant drip rate as the pressure
varies. This will reduce water loss when the
pump is running.
Polyethylene pipe Flexible “poly pipe” (PE)
has proven to tolerate repeated freezing.
Connections may loosen from ice expansion,
but the pipe is not damaged. Poly pipe is
often used in places where pipe may freeze
accidentally or occasionally. See Section 7.3
for precautions regarding PE pipe. If you plan
to bury PE pipe, observe further precautions
supplied by the pipe manufacturer.
Monitoring the water level in your storage
tank Will you be able to observe the level of
water in your tank? If you cannot easily see
into your storage tank, here are some meth-
ods of tank monitoring.
1. dipstick in the air vent
2. float with a visible rod that protrudes
through the top of the tank
3. clear sight-tube alongside the tank
4. precision pressure gauge (note: 1 PSI =
2.3 feet)
To Next Page
Loading...
Need help?
General
