Bosch CA Series - Water-Quality Considerations

Installation, Operation, and Maintenance Manual
CA Series Heat Pumps -8733851021 (2025/04) US
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12 Water-Quality Considerations
NOTICE
Product damage
NOTICE
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Failure to ensure proper water quality and flow rates can shorten the life of the heat
pump and potentially void the unit warranty.
Maintaining proper water quality is important for insuring a long and trouble free
service life for an CA series heat pump. (Refer to the Water Quality Table 6)
For closed loop and boiler/tower systems water chemistry can be checked and
easily maintained to ensure that corrosive elements, dissolved oxygen and pH
levels are kept in check. It is important to ensure that any additive, antifreeze or
corrosion inhibitor that is added to the water loop is compliant with all applicable
laws and regulations and is compatible with copper, brass and bronze alloys.
Ensure that all recommended safety precautions are followed when handling or
adding chemicals to the water loop.
For open loop systems, water quality is very important. Refer to Water Quality
Table on page 20 which shows acceptable ranges for a variety of water quality
factors. The three main concerns in open loop installations are scaling, corrosion
and fouling.
In installations with hard water, scaling due to a buildup of carbonates on the heat
exchanger wall can gradually degrade the heat pump performance over time. Heat
pumps that are affected by scaling may exhibit low suction pressures in heating and
high head pressures in cooling with a gradual loss of capacity and efficiency. Scaled
heat exchangers can be cleaned by a qualified technician but care should be taken
to avoid scaling in the first place.
To limit scaling, water flow rates should be kept at 3 gallons/minute per nominal
cooling ton (a 10°F temperature rise in cooling) and care should be taken to avoid
air in the water lines from suction side leaks.
In installations with high hydrogen sulfide, chlorine or ammonia, corrosion
is a potential problem. In these installations a cupro-nickel heat exchanger is
recommended along with maintaining proper flow and keeping air out of the
system. If water quality is outside of the values in water quality table, then a closed
loop is recommended.
Fouling due to iron bacteria can also pose problems in some open loop
installations. Iron bacteria fouling can quickly degrade system performance and
plug heat exchangers.
Air in the water system will greatly accelerate the fouling or corrosion process.