Distribution Pump |
|
Chiller 1
Chiller 2
Decoupler | Expansion |
| Tank(s) |
Zone 1
Air Separator with Vent
Zone 2
Zone 3
NOTE: Expansion tanks must be disconnected for chillers placed parallel in the primary water loop.
Fig. 13 — Typical Air Separator and Expansion Tank Location on
Step 6 — Fill the Chilled Water Loop
WATER SYSTEM CLEANING — Proper water system cleaning is of vital importance. Excessive particulates in the water system can cause excessive pump seal wear, reduce or stop flow, and cause damage of other components. Water quality should be maintained within the limits indicated in Table 2. Failure to maintain proper water quality may result in heat exchanger failure.
CAUTION
Failure to properly clean all piping and components of the chilled water system before unit
1.Install a temporary bypass around the chiller to avoid cir- culating dirty water and particulates into the pump pack- age and chiller during the flush. Use a temporary circulat- ing pump during the cleaning process. Also, be sure that there is capability to fully drain the system after cleaning. (See Fig 14.)
2.Be sure to use a cleaning agent that is compatible with all system materials. Be especially careful if the system contains any galvanized or aluminum components. Both
3.It is a good idea to fill the system through a water meter. This provides a reference point for the future for loop volume readings, but it also establishes the correct quantity of cleaner needed in order to get the required concentration.
4.Use a feeder/transfer pump to mix the solution and fill the system. Circulate the cleaning system for the length of time recommended by the cleaning agent manufacturer.
a.After cleaning, drain the cleaning fluid and flush the system with fresh water.
b.A slight amount of cleaning residue in the system can help keep the desired, slightly alkaline, water pH of 8 to 9. Avoid a pH greater than 10, since this will adversely affect pump seal components.
c.A side stream filter is recommended (see Fig. 15) during the cleaning process. Filter side flow rate should be enough to filter the entire water volume every 3 to 4 hours. Change filters as often as neces- sary during the cleaning process.
d. Remove temporary bypass when cleaning is complete.
Table 2 — Water Quality Characteristics
and Limitations
WATER CHARACTERISTIC | QUALITY LIMITATION | |
Alkalinity (HCO | 70 – 300 ppm | |
| 3 |
|
Sulfate (SO | Less than 70 ppm | |
| 4 |
|
HCO | Greater than 1.0 | |
3 | 4 |
|
Electrical Conductivity | 10 – 500 μS/cm | |
pH |
| 7.5 – 9.0 |
|
| |
Ammonium (NH3) | Less than 2 ppm | |
Chorides | Less than 300 ppm | |
Free chlorine (Cl2) | Less than 1 ppm | |
Hydrogen Sulfide (H2S)* | Less than 0.05 ppm | |
Free (aggressive) Carbon | Less than 5 ppm | |
Dioxide (CO2)† |
| |
Total Hardness (dH) | 4.0 – 8.5 | |
Nitrate (NO3) | Less than 100 ppm | |
Iron (Fe) | Less than 0.2 ppm | |
Aluminum (Al) | Less than 0.2 ppm | |
Manganese (Mn) | Less than 0.1 ppm | |
*Sulfides in the water quickly oxidize when exposed to air, requiring that no agitation occur as the sample is taken. Unless tested immediately at the site, the sample will require stabilization with a few drops of one Molar zinc acetate solution, allowing accurate sulfide determination up to 24 hours after sampling. A low pH and high alkalinity cause system problems, even when both values are within the ranges shown. The term pH refers to the acidity, basicity, or neutrality of the water supply. Below 7.0, the water is considered to be acidic. Above 7.0, water is considered to be basic. Neutral water contains a pH of 7.0.
†Dissolved carbon dioxide can either be calculated from the pH and
total alkalinity values, shown below, or measured on the site using a test kit. Dissolved Carbon Dioxide, PPM = TA x
= Total Alkalinity, PPM as CaCO3.
FILLING THE SYSTEM — The initial fill of the chilled water system must accomplish three purposes:
1.The entire piping system must be filled with water.
2.The pressure at the top of the system must be high enough to vent air from the system (usually 4 psig is adequate for most vents).
3.The pressure at all points in the system must be high enough to prevent flashing in the piping or cavitation in the pump.
The pressure created by an operating pump affects system pressure at all points except one — the connection of the compression tank to the system. This is the only location in the system where pump operation will not give erroneous pressure indications during the fill. Therefore, the best location to install the fill connection is close to the expansion tank. An air vent should be installed close by to help eliminate air that enters during the fill procedure.
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