Onix Tubing Installation Manual

Systems should not be operated at lev-
els below 30% glycol. Glycol levels
below 25% do not contain enough cor-
rosion inhibitors and may cause the
glycol to act as food, allowing
microbes to grow. The microbes feed,
grow and die, allowing a black sludge
material to form in the system.
Concentrations above 25%, propylene
glycol prevents microbe growth. Try
not to exceed a mixture level greater
than 70% as the fluid may become too
viscous (thick) for the circulators.
As glycol in the system ages, the
inhibitors and buffers added to the sys-
tem begin to break down. This process
slowly returns the system to the natu-
ral pH level of the glycol. If not prop-
erly maintained, glycol in the system
can cause corrosion. Check a glycol
system at least once a year to ensure
the glycol is still within its operating
parameters.
Glycol Maintenance
A glycol system should be checked for
two things: system pH and freeze pro-
tection. The quickest way to check a
glycol system s pH is with litmus
paper. If the pH drops below 7, then
more buffers must be added to a sys-
tem or the system needs to be flushed
and refilled. There are only a limited
number of times buffers can be added
to a system before it must be flushed
and replaced. Check with the glycol
manufacturer for further details. Some
glycol manufacturers will require a
higher minimum pH to be maintained.
Freeze Protection
The second item that must be checked
in a glycol system is the actual level of
freeze protection provided. Watts
Radiant recommends a 50% glycol
solution. However, this does not
always equate to a 50% glycol solu-
tion and 50% water. Different glycol
providers supply different concentra-
tions of glycol and/or may mix a cer-
tain amount of distilled water with the
inhibitors. For example, a glycol that
is already pre-mixed to a 50% level
and then is diluted by the installer with
50/50 water have a true 25% glycol
concentration.
The only way to accurately measure
glycol in a system is to use a refrac-
tometer. A refractometer uses a simple
property of a liquid to determine its
freeze point. Liquid will refract, or
bend light at a known angle. This
angle is a direct correlation to its
freeze point. A refractometer is a
device that measures this deflection. A
basic refractometer is a device that
looks like a kaleidoscope. The user
places a drop of fluid on a lens on one
end and then looks through the other
end. What is seen is a chart that shows
the freeze point.
This should be checked before and
after the glycol is installed. Check a
sample mixture, one cup glycol and
one cup water. Test this solution with
the refractometer to see what the sys-
tem freeze protection will be. Do this
each time the system is re-filled with
new glycol. Also, check the freeze
protection when the system pH is
checked just to make sure the system
is operating within the desired parame-
ters.
Caution: The refractometer used
must be calibrated for propylene
glycol. A refractometer calibrated
for automotive (ethylene) glycol will
not yield accurate results.
Perpendicular installations may be eas-
ier to install on long narrow steps.
This approach will more easily melt
snow and ice that may build up along
the outer step edge. However, it may
require additional rebar to support the
tubing around bends as it moves from
step to step.
In both applications it is important to
keep the Onix 2"—3’’ away from the
surface of the concrete. In some cases
it may be ideal to install a designated
manifold for the steps. This allows for
a dedicated vent/purge assembly to be
used for purging the tubing located in
the steps.
Glycol
Any hydronic system that is exposed
to near or below freezing conditions
must have propylene glycol installed
as the working fluid. Propylene glycol
can prevent the system fluid from
freezing. The level of frost protection
will depend on the glycol concentra-
tion used.
Glycol Basics
Glycol is naturally corrosive. Buffers
and inhibitors are added to offset this
corrosive effect. In addition, glycol
acts like an oxygen grabber , absorb-
ing any free oxygen molecules in the
system. The more oxygen the glycol
grabs , the more acidic it will
become.
10
10
0
-10
-20
-30
-40
Typical Refractometer image as seen
through the view finder. The terminus line
between the shaded area and the light
area represents the freeze level of the fluid
in question. In this case, the fluid being
tested is freeze protected to –15°F.
Snowmelt
Watts Radiant: Onix Installation Manual page 57