Mitsubishi Electric City Multi PWFY-P36NMU-E-BU Data Book page 62

15. INSTALLATION
Water processing and water quality control
To preserve water quality, use the closed type of cooling tower for unit. When the circulating water quality is poor, the water
heat exchanger can develop scales, leading to a reduction in heat-exchange power and possible corrosion of the heat
exchanger.
Please pay careful attention to water processing and water quality control when installing the water circulation system.
Removal of foreign objects or impurities within the pipes.
During installation, be careful that foreign objects, such as welding fragments, sealant particles, or rust, do not enter the
pipes.
Water Quality Processing
a) Depending on the quality of the cold-temperature water used in the air-conditioner, the copper piping of the heat
exchanger may become corroded. We recommend regular water quality processing.
Cold water circulation systems using open heat storage tanks are particularly prone to corrosion.
When using an open-type heat storage tank, install a water-to-water heat exchanger, and use a closed-loop circuit on
the air conditioner side. 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 1mg/liter.
b) Water quality standard
Items
pH
Electric conductivity (mS/m) 77 ˚F (25 ˚C)
(μ s/cm) 77 ˚F (25 ˚C)
Chloride ion
Sulfate ion (mg SO4
Standard
Acid consumption
items
(mg CaCO
Total hardness (mg CaCO
Calcium hardness (mg CaCO
Ionic silica
Refer- Iron
ence Copper
items
Sulfide ion
Ammonium ion (mg NH
Residual chlorine
Free carbon dioxide
Ryzner stability index
Reference: Guideline of Water Quality for Refrigeration and Air Conditioning Equipment. (JRA GL02E-1994)
c) 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.
d) When replacing a previously installed air conditioning device (even when only the heat exchanger is being replaced),
first conduct a water quality analysis and check for possible corrosion.
Corrosion can occur in cold-water systems even if there has been no prior signs of corrosion.
If the water quality level has dropped, please adjust water quality sufficiently before replacing the unit.Refer to the below
graph for the maximum amount of circulating water in the water pipe. Make sure that this amount does not exceed.
[Fig. 3-1-D] Maximum circulating water
PWFY-P36NMU-E-BU
500
400
300
200
Available water volume area
100
0
0 10 20
Condition: Water outlet temp. 160°F (71°C)
MEES20K028
Lower mid-range temperature water
system Water Temp. =< 140 ˚F (60 ˚C)
Recirculating water
77 ˚F (25 ˚C) 7.0 ~ 8.0
30 or less
[300 or less]
-
(mg Cl /liter) 50 or less
2-
/liter) 50 or less
(pH4.8)
50 or less
/liter)
3
/liter)
70 or less
3
/liter) 50 or less
3
(mg SiO /liter) 30 or less
2
(mg Fe/liter) 1.0 or less
(mg Cu/liter) 1.0 or less
not to be
2-
(mg S /liter)
detected
/liter) 0.3 or less
4+
(mg Cl/liter) 0.25 or less
(mg CO /liter) 0.4 or less
2
–
30 40 50 60
Total hardness [mg/L]
Higher mid-range temperature water
system Water Temp. > 140 ˚F (60 ˚C)
Recirculating water
Make-up water
7.0 ~ 8.0 7.0 ~ 8.0
30 or less 30 or less
[300 or less] [300 or less]
50 or less 30 or less
50 or less 30 or less
50 or less
50 or less
70 or less
70 or less
50 or less 50 or less
30 or less 30 or less
0.3 or less 1.0 or less
1.0 or less 1.0 or less
not to be not to be
detected detected
0.1 or less 0.1 or less
0.3 or less 0.1 or less
4.0 or less 0.4 or less
– –
PWFY-P36/72NMU-E2-AU
3000
2500
2000
1500
1000
Available water volume area
500
0
70 0 10 20
Condition: Water outlet temp. 113°F (45°C)
AIR TO WATER
Tendency
Make-up water Corrosive Scale-forming
7.0 ~ 8.0
30 or less
[300 or less]
30 or less
30 or less
50 or less
70 or less
50 or less
30 or less
0.3 or less
1.0 or less
not to be
detected
0.1 or less
0.3 or less
4.0 or less
–
30 40 50 60
Total hardness [mg/L]
70
61