Water Quality Standards - Zehnder Rittling HP Series Installation, Operation And Maintenance Manual

Water quality standards

Proper maintenance of the
water loop is critical to both the
efficiency and longevity of the
system. This includes cleaning,
flushing and chemical treatment.
Three categories of issues can
arise from use of water including:
Scale formation: resulting
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from crystallization of
dissolved salts in the water.
These deposits form a
water-side insulation layer
that reduces heat transfer,
increases pressure drop and
may reduce flow.
Metal decay: resulting from
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corrosion or erosion
Table 6: Water characteristics
Impurity Copper coils
Calcium and
magnesium salts <350 PPM
(hardness)
Iron oxide Low levels only Moderate levels
pH 7.0 - 8.5
Hydrogen sulfide <10 PPM
CO <50 PPM
2
Chloride <300 PPM
Total dissolved solids <100 PPM
Slime and algae can form under
Slime and algae
certain environmental conditions
Notes:
Water quality varies widely from locale to locale. Consult a local water treatment specialist for specific treatment recommendations.
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Cupro-nickel is recommended if iron bacteria, suspended solids, or dissolved oxygen is high.
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If concentration of corrosives exceeds Cupro-nickel maximums the potential for serious corrosion problems exist.
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Organic growths: slime and
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algae can form under certain
environmental conditions. These
growths can have multiple adverse
impacts including reduced heat
transfer, increased pressure drop,
reduced flow and corrosion.
System water should be evaluated
for impurities. Testing is available
from independent labs, health
departments and/or state agencies.
Table 6 provides a list of water
characteristics, potential impurities
and effects and recommended
treatments.
Cupro-nickel
Result
coils
350 PPM sea
Scaling
water
5 - 10
10-50 PPM
Corrosion
50-75 PPM
300-600 PPM
1000-1500 PPM
Reduced heat transfer
due to forming of
insulating coating or
pitting due to corrosion
Potential problems can be
mitigated by:
Using cupro-nickel coils
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Maintaining flow rates of
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<4 GPM per ton to minimize
potential erosion
The Zehnder Rittling Water
Quality Table provides water
quality requirements for Zehnder
Rittling coaxial heat exchangers.
When water properties are
outside of those requirements,
an external secondary heat
exchanger must be used to
isolate the heat pump heat
exchanger from the unsuitable
water. Failure to do so will void
the warranty for the coaxial heat
exchanger.
Application
Open recirculating
1. Bleed off
2. Surface active agents such
as polyphosphates
3. Addition of acid
4. pH adjustment
1. Corrosion inhibiters 1. Corrosion inhibiters
2. pH control
3. Proper materials of 2. Proper materials of
construction
1. Chlorinated phenols
2. Other biocides
3. Chlorine by hypochlorites ot
by liquid chlorine
Closed recirculating
No treatment required
(high concentrations)
construction
No treatment required
Water quality standards 17