Plumbing Connection 2-2015

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8 6 PLUMBING CONNECTION WINTER 2015
including digital display and adjustable
temperature differentials (for most
models). They also quote to have an
IP rating of IP54. These controllers
were made to suit the manufactures’
requirements when produced and you
may come across several branded
versions of this controller that work
the same. Replacement boards are still
available.
Older model roof sensors had
the white Teflon coating for higher
temperature rating. This has changed.
The new roof sensor cable still has
the Teflon but it is encased by a black
silicon cable. The problem is that they
now look similar to the tank sensor
which means people occasionally think
they can use the tank sensor on the
roof because it works out cheaper.
Don’t though. They have different
sensor ratings.
TANK SENSOR
Tank sensor positioning on some of
the older models is really worth looking
at when you go out to repair a system.
Check where they have been installed.
They could be anywhere. A couple of
examples include taped to a pipe or
pushed between the flow pipe and the
pipe insulation. Some of the older and
bigger 315L to 400L tanks had an inlet
Tee’s with the tank sensor and solar
flow all in one. Some of these sensor
ports only went into the tank as little
as 50 mm. The tank sensor needs to
be positioned differently so it is more
accurate and the system becomes a
little more efficient.
Sensor ports can be extended but
sometimes you are best to try to
move the sensor up the tank a couple
hundred millimeters’ depending on the
system and the return line positioning.
This takes the tank sensor away from
the cold water inlet and solar return
line. It can create a more accurate
reading which can help the pump and
internals of the tank to last longer.
The S3 sensor by Senztek is probably
one of the more handy options you
may come across but it depends on the
system you’re working on. It only works
with the Senztek controller but it can
be retrofitted into the outer casing of
the tank in any position.
One thing to check before using a
product like this is the effect it may
have on the warranty of the tank. It is
then important to explain the findings
to the customer before installation.
These types of sensor are more
commonly used in some of the original
evacuated tube type systems but can
also be used with split systems with
flat panels.
Mathew Briggs is a commercial
plumber and director of www.
–
specialising in solar hot water
replacement parts for all systems.
SOLAR HOT WATER SYSTEM REVIVAL
For this edition we have put together a
solar hot water revival on an old Saxon split
solar hot water system, also known as the
SP4002 split water heater.
I was unable to tell how long it was
since this system had actually worked
so the owner had the plumber install a
pump station designed for this model
and it was very successful. To make this
work he has had an electrician install an
external power point for the new pump
station. At the same time the electrician
has disconnected the original controller
and pump from the circuit used to power
the element.
The Viking pump has been replaced with
the upgraded option, the Grundfos 15 65
B , a flow meter and non return valve has
been installed. Both sensors have been
replaced with the new controller; the
tank inlet immersion sleeve has also been
replaced. While replacing the roof sensor
the air admittance valve was replaced with
an AEHT-10. Once everything was installed
the time consuming part was to bleed the
air from the collector and tank again. This
may need to be done a few times.
You will most commonly find these
systems in large housing estates. The
system was not your typical open loop
solar hot water system that some
plumbers mistake it for. It is basically a
low-pressure closed loop system, which
means it needs a slightly different pump
to your normal closed loop system. They
originally used an imported cheaper Viking
pump and towards the end of manufacture
this was replaced by the Grundfos 15 65B.
The Grundfos 15 65 B can still be bought
for this model it is a less expensive option
of the Grundfos 20 60N but both pumps
work fine. The controller is commonly
a PCB board in the side of the tank, but
there are some variations of this system
when it comes to how the system was set
up. Sensors can still be bought for these
systems. Some variations of this system
have the element and controller powered
off the same circuit. Because of this set up
most people do not know the solar part of
their system has not worked for years!
LEFT: Incorrect sensor installations are common as seen here where it was wedged
between the flow pipe and insulation. RIGHT: A Senztek s3 replacement sensor.
Solar Hot Water Parts
SOLAR FIX
MATHEW BRIGGS