10
Air Handling Units
Connection of Heat Exchangers
Water Connected Air-handling Component
Installation
Recommendations on water quality for heat exchangers
that operate using low pressure hot water (LPHW) and
chilled water:
A good water quality – e.g. salt and lime-free drinking
water – increases the
lifetime and efficiency of the heat exchanger.
Check the limiting values shown in the table annually to
prevent damage to
the hydraulic system and its components.
If necessary inhibitors must be added.
Note:
These limiting values are only basic information about the
water quality and do not form any basis for a guarantee!
1/1,78 °D = 1 °Fr, with 1°Fr = 10 g CaCO
3
/m
3
ppm = parts per million (mg/l)
ppm = parts per billion (µg/l)
Description
Symbol
Values
Effects in vent
of deviation
Hydrogen ion
concentration
pH
7,5 - 9
< 7
> 9
Corrosion
Fouling
Calcium and
magnesium content
Hard-
ness
(Ca/Mg)
4 – 8,5 °D > 8,5
Fouling
Chloride ions
Cl-
< 50 ppm
Corrosion
Carbon dioxide
Fe
3+
< 0,5 ppm
Corrosion
Iron ions
Mg
2+
< 0,05
ppm
Corrosion
Carbon dioxide
CO
2
< 10 ppm
Corrosion
Hydrogen sulphate
H
2
S
< 50 ppb
Corrosion
Oxygen
O
2
< 0,1 ppm
Corrosion
Chlorine
Cl
2
< 0,5 ppm
Corrosion
Ammonia
NH
3
< 0,5 ppm
Corrosion
Ratio of carbons/
sulphates
HCO
3
2-
/
SO
4
2-
>1
<1
Corrosion
