Mitsubishi Electric E Series, Service Handbook

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[
II
Restrictions ]
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HWE1417B GB
3. Notes on pipe corrosion
Water treatment and water quality control
Poor-quality circulating water can cause the water-side heat exchanger to scale up or corrode, reducing heat-
exchange performance. Properly control the quality of the circulating water.
• Removing foreign objects and impurities in the pipes
During installation, keep foreign objects, such as welding and sealant fragments and rust, out of the pipes.
• Water Quality Control
(1) Poor-quality water can corrode or scale up the heat exchanger. Regular water treatment is recommended.
Water circulation systems using open heat storage tanks are particularly prone to corrosion.
When using an open heat storage tank, install a water-to-water heat exchanger, and use a closed-loop circuit.
If a water supply tank is installed, keep contact with air to a minimum, and keep the level of dissolved oxygen in
the water no higher than 1 mg/ℓ.
(2) Water quality standard
Reference: Guideline of Water Quality for Refrigeration and Air Conditioning Equipment. (JRA GL02E-1994)
(3) Please consult with a water quality control specialist about water quality control methods and water quality
calculations before using anti-corrosive solutions for water quality management.
(4) When replacing an air conditioner (including when only the heat exchanger is replaced), first analyze the water
quality and check for possible corrosion.
Corrosion can occur in water systems in which there has been no signs of corrosion. If the water quality level
has dropped, adjust the water quality before replacing the unit.
Items
Lower mid-range temperature water system
Water Temp. ≤ 60ºC
Higher mid-range temperature water system
Water Temp. > 60ºC
Tendency
Recirculating water Make-up water Recirculating water Make-up water Corrosive
Scale-
forming
Standard
items
pH (25°C)
Electric conductivity (mS/m) (25°C)
30 or less
30 or less 30 or less 30 or less
(μs/cm) (25°C) [300 or less] [300 or less] [300 or less] [300 or less]
Chloride ion
(mg Cl
-
/ℓ)
50 or less 50 or less 30 or less 30 or less
Sulfate ion
(mg SO4
2-
/ℓ)
50 or less 50 or less 30 or less 30 or less
Acid consumption
50 or less 50 or less 50 or less 50 or less
(pH4.8) (mg CaCO
3
/ℓ)
Total hardness
(mg CaCO
3
/ℓ)
70 or less 70 or less 70 or less 70 or less
Calcium hardness
(mg CaCO
3
/ℓ)
50 or less 50 or less 50 or less 50 or less
Ionic silica
(mg SiO
2
/ℓ)
30 or less 30 or less 30 or less 30 or less
Reference
items
/ e F g m ( n o r I ℓ) 1.0 or less 0.3 or less 1.0 or less 0.3 or less
Copper (mg Cu/ℓ) 1.0 or less 1.0 or less 1.0 or less 1.0 or less
Sulfide ion
(mg S
2-
/ℓ) Not to be detected Not to be detected Not to be detected Not to be detected
Ammonium ion (mg NH
4
+
/ℓ) 0.3 or less 0.1 or less 0.1 or less 0.1 or less
Residual chlorine (mg Cl/ ℓ) 0.25 or less 0.3 or less 0.1 or less 0.3 or less
Free carbon dioxide
(mg CO
2
/ℓ)
0.4 or less 4.0 or less 0.4 or less 4.0 or less
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