In order to prevent scaling and corrosion in cooling circuits, certain limit and guidelines values in the circulation water need to be maintained. The specifications of the respective manufacturer are authoritative for that purpose. Within Germany, those are usually geared towards the VDI guideline "VDI 3803: Air-conditioning Systems - Structural and Technical Principles".
The limit and guideline values listed below are geared towards VDI 3803.
The concentration factor of the circuit water is calculated based upon the evaporation quantity and the blow-down quanity. Blow-down is usually conducted depending upon conducitvity. However, none of the listed limit values may be exceeded. Accordingly, the permitted concentration factor depends upon the limit values for the circulation water, and is thus influenced by the quality of the make-up water and accordingly the make-up water treatment. A concentration factor of about 3 ... 5 is usually economically expedient.
| Surface and pipeline material | carbon steel, non-ferrous metal | carbon steel, synthetic material | stainless steel | |
| Quantity | Unit | |||
| pH-value | 7.5 ... 8.5 | |||
| salt content | ppm | < 1800 | < 2100 | < 2500 |
| conductivity | μS/cm | < 2200 | < 2500 | < 3000 |
| calcium | ppm | > 20 | > 20 | - |
|
total alkaline earths (w/o dosing of antiscaling agents) |
mmol/l | ≥ 0.5 | ||
|
acid capacity KS 4,3 (w/o dosing of antiscaling agents) |
mmol/l | < 2.0 | ||
|
acid capacity KS 4,3 (with dosing of polyphosphate) |
mmol/l | < 3.5 | ||
|
acid capacity KS 4,3 (with dosing of organophosphate) |
mmol/l | < 7.0 | ||
| chloride | ppm | < 200 | < 250 | < 400 |
| sulphate | ppm | < 325 | < 400 | < 600 |
| iron | ppm | < 0.1 | ||
| manganese | ppm | < 0.1 | ||
| copper | ppm | < 0.5 | ||
| oxidability Mn VII - II | ppm | < 25 | ||