14
Enertech Global IOM, XT Models
Water Quality
The quality of the water used in geothermal
systems is very important. In closed loop systems the
dilution water (water mixed with antifreeze) must
be of high quality to ensure adequate corrosion
protection. Water of poor quality contains ions that
make the uid “hard” and corrosive. Calcium and
magnesium hardness ions build up as scale on the
walls of the system and reduce heat transfer. These
ions may also react with the corrosion inhibitors
in glycol based heat transfer uids, causing them
to precipitate out of solution and rendering the
inhibitors ineffective in protecting against corrosion.
In addition, high concentrations of corrosive ions,
such as chloride and sulfate, will eat through any
protective layer that the corrosion inhibitors form on
the walls of the system.
Ideally, de-ionized water should be used for dilution
with antifreeze solutions since de-ionizing removes
both corrosive and hardness ions. Distilled water
and zeolite softened water are also acceptable.
Softened water, although free of hardness ions, may
actually have increased concentrations of corrosive
ions and, therefore, its quality must be monitored.
It is recommended that dilution water contain less
than 100 PPM calcium carbonate or less than 25
PPM calcium plus magnesium ions; and less than 25
PPM chloride or sulfate ions.
In an open loop system the water quality is of no
less importance. Due to the inherent variation of the
supply water, it should be tested prior to making the
decision to use an open loop system. Scaling of the
heat exchanger and corrosion of the internal parts
are two of the potential problems. The Department
of Natural Resources or your local municipality can
direct you to the proper testing agency. Please see
following table for guidelines.
Removing Debris During Purging
Most ow center or pump failures are a result of
poor water quality or debris. Debris entering the loop
during fusion and installation can cause noise aand
premature pump failure. Enertech recommends a
double ush ltering method during purging. When
purging, use a 100 micron bag lter until air bubbles
are removed. Remove the 100 micron bag, replace
it with a 1 micron bag and restart the ushing.
Water Quality Guidelines
Section 5: Unit Piping Installation
Potential
Problem
Chemical(s) or Condition
Range for Copper
Heat Exchangers
Cupro-Nickel Heat
Exchanger Ranges
Stainless Steel Heat
Exchanger Ranges
Scaling
Calcium & Magnesium
Carbonate
Less than 350 ppm Less than 350 ppm Less than 0.1 ppm
Corrosion
pH Range 7 - 9 5 - 9 7 - 9
Total Dissolved Solids Less than 1000 ppm Less than 1500 ppm No rigid setpoint
Ammonia, Ammonium
Hydroxide
Less than 0.5 ppm Less than 0.5 ppm No Limit
Ammonium Chloride,
Ammonium Nitrate
Less than 0.5 ppm Less than 0.5 ppm Less than 2-20 ppm
Calcium/Sodium Chloride
See Note 4
Less than 125 ppm Less than 125 ppm None Allowed
Chlorine Less than 0.5 ppm Less than 0.5 ppm Less than 1 ppm*
Hydrogen Sulde None Allowed None Allowed Less than 0.05 ppm
Biological
Growth
Iron Bacteria None Allowed None Allowed None Allowed
Iron Oxide Less than 1 ppm Less than 1 ppm Less than 0.2 ppm
Erosion
Suspended Solids - Note 5 Less than 10 ppm Less than 10 ppm
16-20 mesh strainer
recommended
Water Velocity Less than 8 ft/s Less than 12 ft/s
Less than 5.5 m/s in the
port
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